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1. First Measurement of $a^0_2(1320)$ Polarized Photoproduction Cross Section

Author: GlueX Collaboration, Afzal, F., Akondi, C. S., Albrecht, M., Amaryan, M., Arrigo, S., Arroyave, V., Asaturyan, A., Austregesilo, A., Baldwin, Z., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Barton, D., Baturin, V., Berdnikov, V. V., Black, T., Boeglin, W., Boer, M., Briscoe, W. J., Britton, T., Cao, S., Chudakov, E., Chung, G., Cole, P. L., Cortes, O., Crede, V., Dalton, M. M., Darulis, D., Deur, A., Dobbs, S., Dolgolenko, A., Dugger, M., Dzhygadlo, R., Ebersole, D., Edo, M., Egiyan, H., Erbora, T., Eugenio, P., Fabrizi, A., Fanelli, C., Fang, S., Fitches, J., Foda, A. M., Furletov, S., Gan, L., Gao, H., Gardner, A., Gasparian, A., Glazier, D. I., Gleason, C., Goryachev, V. S., Grube, B., Guo, J., Guo, L., Hernandez, J., Hernandez, K., Hoffman, N. D., Hornidge, D., Hou, G., Hurck, P., Hurley, A., Imoehl, W., Ireland, D. G., Ito, M. M., Jaegle, I., Jarvis, N. S., Jeske, T., Jing, M., Jones, R. T., Kakoyan, V., Kalicy, G., Khachatryan, V., Kourkoumelis, C., LaDuke, A., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Liu, B., Livingston, K., Lolos, G. J., Lorenti, L., Lyubovitskij, V., Ma, R., Mahmood, A., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mizutani, K., Moran, P., Neelamana, V., Ng, L., Nissen, E., Orešić, S., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Pedroni, R., Pentchev, L., Peters, K. J., Prather, E., Veetil, L. Puthiya, Rakshit, S., Reinhold, J., Remington, A., Ritchie, B. G., Ritman, J., Rodriguez, G., Romanov, D., Saldana, K., Salgado, C., Schadmand, S., Schertz, A. M., Scheuer, K., Schick, A., Schmidt, A., Schumacher, R. A., Schwiening, J., Scott, M., Septian, N., Sharp, P., Shen, X., Shepherd, M. R., Sikes, J., Smith, A., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Stevens, J. R., Strakovsky, I. I., Sumner, B., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Viducic, T., Whitlatch, T., Wickramaarachchi, N., Wunderlich, Y., Yu, B., Zarling, J., Zhang, Z., Zhou, X., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: We measure for the first time the differential photoproduction cross section $d\sigma/dt$ of the $a_2(1320)$ meson at an average photon beam energy of 8.5~GeV, using data with an integrated luminosity of 104~pb$^{-1}$ collected by the GlueX experiment. We fully reconstruct the $\gamma p \to \eta\pi^0 p$ reaction and perform a partial-wave analysis in the $a_2(1320)$ mass region with amplitudes that incorporate the linear polarization of the beam. This allows us to separate for the first time the contributions of natural- and unnatural-parity exchanges. These measurements provide novel information about the photoproduction mechanism, which is critical for the search for spin-exotic states., Comment: 8 pages, 4 figures plus supplemental material
Published: 2025

2. EWOCS-III: JWST observations of the supermassive star cluster Westerlund 1

Author: Guarcello, M. G., Almendros-Abad, V., Lovell, J. B., Monsch, K., Muzic, K., Martiinez-Galarza, J. R., Drake, J. J., Anastasopoulou, K., Andersen, M., Argiroffi, C., Bayo, A., Bonito, R., Capela, D., Damiani, F., Gennaro, M., Ginsburg, A., Grebel, E. K., Hora, J. L., Moraux, E., Najarro, F., Negueruela, I., Prisinzano, L., Richardson, N. D., Ritchie, B., Robberto, M., Rom, T., Sabbi, E., Sciortino, S., Umana, G., Winter, A., Wright, N. J., and Zeidler, P.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract: The typically large distances, extinction, and crowding of Galactic supermassive star clusters have so far hampered the identification of their very low mass members, required to extend our understanding of star and planet formation, and early stellar evolution, to starburst. This situation has now evolved thanks to the James Webb Space Telescope (JWST), and its unmatched resolution and sensitivity in the infrared. In this paper, the third of the series of the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS), we present JWST/NIRCam and JWST/MIRI observations of the supermassive star cluster Westerlund 1. These observations are specifically designed to unveil the cluster members down to the BD mass regime, and to allow us to select and study the protoplanetary disks and to study the mutual feedback between the cluster members and the surrounding environment. Westerlund 1 was observed as part of JWST GO-1905 for 23.6 hours. The data have been reduced using the JWST calibration pipeline, together with specific tools necessary to remove artifacts. Source identification and photometry were performed with DOLPHOT. The MIRI images show a plethora of different features. Diffuse nebular emission is observed around the cluster, which is typically composed of myriads of droplet-like features pointing toward the cluster center or the group of massive stars surrounding the WR star W72/A. A long pillar is also observed in the NW. The MIRI images also show resolved shells and outflows surrounding the M-type RSG W20, W26, W75, and W237, the sgB[e] star W9 and the YHG W4. The color-magnitude diagrams built using the NIRCam photometry show a clear cluster sequence, which is marked in its upper part by the 1828 NIRCam stars with X-ray counterparts. NIRCam observations using the F115W filter have reached the 23.8 mag limit with 50\% completeness (roughly corresponding to a 0.06 Msol brown dwarf)., Comment: Accepted for publication in Astronomy & Astrophysics
Published: 2024

3. EWOCS-II: X-ray properties of the Wolf-Rayet stars in the young Galactic super star cluster Westerlund 1

Author: Anastasopoulou, K., Guarcello, M. G., Flaccomio, E., Sciortino, S., Benatti, S., De Becker, M., Wright, N. J., Drake, J., Albacete-Colombo, J. F., Andersen, M., Argiroffi, C., Bayo, A., Castellanos, R., Gennaro, M., Grebel, E. K., Miceli, M., Najarro, F., Negueruela, I., Prisinzano, L., Ritchie, B., Robberto, M., Sabbi, E., and Zeidler, P.
Subjects: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract: We present the most comprehensive and deepest X-ray study to date of the properties of the richest Wolf-Rayet (WR) population observed in a single stellar cluster, Westerlund 1 (Wd1). This work is based on 36 Chandra observations obtained from the "Extended Westerlund 1 and 2 Open Clusters Survey" (EWOCS) project, plus 8 archival Chandra observations. The overall exposure depth (~1.1 Ms) and baseline of the EWOCS observations extending over more than one year enable us to perform a detailed photometric, colour, and spectral analysis, as well as to search for short- and long-term periodicity. In X-rays, we detect 20 out of the 24 known Wolf-Rayet stars in Wd1 down to an observed luminosity of ~7$\times10^{29}$erg s$^{-1}$ (assuming a distance of 4.23 kpc to Wd1), with 8 WR stars being detected in X-rays for the first time. Nine stars show clear evidence of variability over the year-long baseline, with clear signs of periodicity. The X-ray colours and spectral analysis reveal that the vast majority of the WR stars are hard X-ray sources (kT$\geq$2.0keV). The Fe XXV emission line at ~6.7 keV, which commonly originates from the wind-wind collision zone in binary systems, is detected for the first time in the spectra of 17 WR stars in Wd1. In addition the ~6.4 keV fluorescent line is observed in the spectra of three stars, indicating that dense cold material coexists with the hot gas in these systems. Overall, our X-ray results alone suggest a very high binary fraction ($\geq$80%) for the WR star population in Wd1. When combining our results with properties of the WR population from other wavelengths, we estimate a binary fraction of $\geq$92%, which could even reach unity. This suggests that either all the most massive stars are found in binary systems within Wd1, or that binarity is essential for the formation of such a rich population of WR stars., Comment: 20 pages, 11 figures, 6 tables, accepted for publication in A&A
Published: 2024

4. Upper Limit on the Photoproduction Cross Section of the Spin-Exotic $\pi_1(1600)$

Author: GlueX Collaboration, Afzal, F., Akondi, C. S., Albrecht, M., Amaryan, M., Arrigo, S., Arroyave, V., Asaturyan, A., Austregesilo, A., Baldwin, Z., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Barton, D., Baturin, V., Berdnikov, V. V., Black, T., Boeglin, W., Boer, M., Briscoe, W. J., Britton, T., Cao, S., Chudakov, E., Chung, G., Cole, P. L., Cortes, O., Crede, V., Dalton, M. M., Darulis, D., Deur, A., Dobbs, S., Dolgolenko, A., Dugger, M., Dzhygadlo, R., Ebersole, D., Edo, M., Egiyan, H., Erbora, T., Eugenio, P., Fabrizi, A., Fanelli, C., Fang, S., Fitches, J., Foda, A. M., Furletov, S., Gan, L., Gao, H., Gardner, A., Gasparian, A., Glazier, D., Gleason, C., Goryachev, V. S., Grube, B., Guo, J., Guo, L., Hernandez, J., Hernandez, K., Hoffman, N. D., Hornidge, D., Hou, G., Hurck, P., Hurley, A., Imoehl, W., Ireland, D. G., Ito, M. M., Jaegle, I., Jarvis, N. S., Jeske, T., Jing, M., Jones, R. T., Kakoyan, V., Kalicy, G., Khachatryan, V., Kourkoumelis, C., LaDuke, A., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Liu, B., Livingston, K., Lolos, G. J., Lorenti, L., Lyubovitskij, V., Ma, R., Mack, D., Mahmood, A., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mizutani, K., Neelamana, V., Ng, L., Nissen, E., Orešić, S., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Pedroni, R., Pentchev, L., Peters, K. J., Prather, E., Rakshit, S., Reinhold, J., Remington, A., Ritchie, B. G., Ritman, J., Rodriguez, G., Romanov, D., Saldana, K., Salgado, C., Schadmand, S., Schertz, A. M., Scheuer, K., Schick, A., Schmidt, A., Schumacher, R. A., Schwiening, J., Septian, N., Sharp, P., Shen, X., Shepherd, M. R., Sikes, J., Smith, A., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Stevens, J. R., Strakovsky, I. I., Sumner, B., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Viducic, T., Whitlatch, T., Wickramaarachchi, N., Wunderlich, Y., Yu, B., Zarling, J., Zhang, Z., Zhou, X., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: The spin-exotic hybrid meson $\pi_{1}(1600)$ is predicted to have a large decay rate to the $\omega\pi\pi$ final state. Using 76.6~pb$^{-1}$ of data collected with the GlueX detector, we measure the cross sections for the reactions $\gamma p \to \omega \pi^+ \pi^- p$, $\gamma p \to \omega \pi^0 \pi^0 p$, and $\gamma p\to\omega\pi^-\pi^0\Delta^{++}$ in the range $E_\gamma =$ 8-10 GeV. Using isospin conservation, we set the first upper limits on the photoproduction cross sections of the $\pi^{0}_{1}(1600)$ and $\pi^{-}_{1}(1600)$. We combine these limits with lattice calculations of decay widths and find that photoproduction of $\eta'\pi$ is the most sensitive two-body system to search for the $\pi_1(1600)$., Comment: 7 pages, 3 figures plus supplemental materials
Published: 2024
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5. Measurement of Spin-Density Matrix Elements in $\Delta^{++}(1232)$ photoproduction

Author: Afzal, F., Akondi, C. S., Albrecht, M., Amaryan, M., Arrigo, S., Arroyave, V., Asaturyan, A., Austregesilo, A., Baldwin, Z., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Barton, D., Baturin, V., Berdnikov, V. V., Black, T., Boeglin, W., Boer, M., Briscoe, W. J., Britton, T., Cao, S., Chudakov, E., Chung, G., Cole, P. L., Cortes, O., Crede, V., Dalton, M. M., Darulis, D., Deur, A., Dobbs, S., Dolgolenko, A., Dugger, M., Dzhygadlo, R., Ebersole, D., Edo, M., Egiyan, H., Erbora, T., Eugenio, P., Fabrizi, A., Fanelli, C., Fang, S., Fitches, J., Foda, A. M., Furletov, S., Gan, L., Gao, H., Gardner, A., Gasparian, A., Glazier, D. I., Gleason, C., Goryachev, V. S., Grube, B., Guo, J., Guo, L., Hernandez, J., Hernandez, K., Hoffman, N. D., Hornidge, D., Hou, G., Hurck, P., Hurley, A., Imoehl, W., Ireland, D. G., Ito, M. M., Jaegle, I., Jarvis, N. S., Jeske, T., Jing, M., Jones, R. T., Kakoyan, V., Kalicy, G., Khachatryan, V., Kourkoumelis, C., LaDuke, A., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Liu, B., Livingston, K., Lolos, G. J., Lorenti, L., Lyubovitskij, V., Ma, R., Mack, D., Mahmood, A., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mizutani, K., Neelamana, V., Ng, L., Nissen, E., Orešić, S., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Pedroni, R., Pentchev, L., Peters, K. J., Prather, E., Rakshit, S., Reinhold, J., Remington, A., Ritchie, B. G., Ritman, J., Rodriguez, G., Romanov, D., Saldana, K., Salgado, C., Schadmand, S., Schertz, A. M., Scheuer, K., Schick, A., Schmidt, A., Schumacher, R. A., Schwiening, J., Septian, N., Sharp, P., Shen, X., Shepherd, M. R., Sikes, J., Smith, A., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Stevens, J. R., Strakovsky, I. I., Sumner, B., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Viducic, T., Whitlatch, T., Wickramaarachchi, N., Wunderlich, Y., Yu, B., Zarling, J., Zhang, Z., Zhou, X., and Zihlmann, B.
Subjects: Nuclear Experiment
Abstract: We measure the spin-density matrix elements (SDMEs) of the $\Delta^{++}(1232)$ in the photoproduction reaction $\gamma p \to \pi^-\Delta^{++}(1232)$ with the GlueX experiment in Hall D at Jefferson Lab. The measurement uses a linearly--polarized photon beam with energies from $8.2$ to $8.8$~GeV and the statistical precision of the SDMEs exceeds the previous measurement by three orders of magnitude for the momentum transfer squared region below $1.4$ GeV$^2$. The data are sensitive to the previously undetermined relative sign between couplings in existing Regge-exchange models. Linear combinations of the extracted SDMEs allow for a decomposition into natural and unnatural--exchange amplitudes. We find that the unnatural exchange plays an important role in the low momentum transfer region.
Published: 2024

6. EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Westerlund 1 and 2 Open Clusters Survey

Author: Guarcello, M. G., Flaccomio, E., Albacete-Colombo, J. F., Almendros-Abad, V., Anastasopoulou, K., Andersen, M., Argiroffi, C., Bayo, A., Bartlett, E. S., Bastian, N., De Becker, M., Best, W., Bonito, R., Borghese, A., Calzetti, D., Castellanos, R., Cecchi-Pestellini, C., Clark, S., Clarke, C. J., Zelati, F. Coti, Damiani, F., Drake, J. J., Gennaro, M., Ginsburg, A., Grebel, E. K., Hora, J. L., Israel, G. L., Lawrence, G., Locci, D., Mapelli, M., Martinez-Galarza, J. R., Micela, G., Miceli, M., Moraux, E., Muzic, K., Najarro, F., Negueruela, I., Nota, A., Pallanca, C., Prisinzano, L., Ritchie, B., Robberto, M., Rom, T., Sabbi, E., Scholz, A., Sciortino, S., Trigilio, C., Umana, G., Winter, A., Wright, N. J., and Zeidler, P.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Context. With a mass exceeding several 10^4 solar masses and a rich and dense population of massive stars, supermassive young star clusters represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions among stars. Aims. In this paper we present the "Extended Westerlund 1 and 2 Open Clusters Survey" (EWOCS) project, which aims to investigate the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars. The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun. Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically, the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec. Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation were carried out using the ACIS-Extract software. Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a photon flux threshold of approximately 2x10^-8 photons/cm^2/s. The X-ray sources exhibit a highly concentrated spatial distribution, with 1075 sources located within the central 1 arcminute. We have successfully detected X-ray emissions from 126 out of the 166 known massive stars of the cluster, and we have collected over 71000 photons from the magnetar CXO J164710.20-455217, Comment: The paper has been accepted for publication by Astronomy and Astrophysics
Published: 2023

7. Measurement of Spin-Density Matrix Elements in $\rho(770)$ Production with a Linearly Polarized Photon Beam at $E_\gamma = 8.2\,-\,8.8\,\text{GeV}$

Author: GlueX Collaboration, Adhikari, S., Afzal, F., Akondi, C. S., Albrecht, M., Amaryan, M., Arroyave, V., Asaturyan, A., Austregesilo, A., Baldwin, Z., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Briscoe, W. J., Britton, T., Brooks, W. K., Byer, D., Chudakov, E., Cole, P. L., Cortes, O., Crede, V., Dalton, M. M., Darulis, D., Deur, A., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Ebersole, D., Edo, M., Egiyan, H., Erbora, T., Eugenio, P., Fabrizi, A., Fanelli, C., Fang, S., Fegan, S., Fitches, J., Foda, A. M., Furletov, S., Gan, L., Gao, H., Gardner, A., Gasparian, A., Gleason, C., Goetzen, K., Goryachev, V. S., Grube, B., Guo, J., Guo, L., Hague, T. J., Hakobyan, H., Hernandez, J., Hoffman, N. D., Hornidge, D., Hou, G., Huber, G. M., Hurck, P., Hurley, A., Imoehl, W., Ireland, D. G., Ito, M. M., Jaegle, I., Jarvis, N. S., Jeske, T., Jones, R. T., Kakoyan, V., Kalicy, G., Khachatryan, V., Khatchatryan, M., Kourkoumelis, C., LaDuke, A., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Liu, B., Livingston, K., Lolos, G. J., Lorenti, L., Lyubovitskij, V., Ma, R., Mack, D., Mahmood, A., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mizutani, K., Neelamana, V., Ng, L., Nissen, E., Orešić, S., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Pedroni, R., Pentchev, L., Peters, K. J., Prather, E., Rakshit, S., Reinhold, J., Remington, A., Ritchie, B. G., Ritman, J., Rodriguez, G., Romanov, D., Saldana, K., Salgado, C., Schadmand, S., Schertz, A. M., Scheuer, K., Schick, A., Schmidt, A., Schumacher, R. A., Schwiening, J., Sharp, P., Shen, X., Shepherd, M. R., Smith, A., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Stevens, J. R., Strakovsky, I. I., Sumner, B., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Viducic, T., Whitlatch, T., Wickramaarachchi, N., Williams, M., Wunderlich, Y., Yu, B., Zarling, J., Zhang, Z., Zhao, Z., Zhou, J., Zhou, X., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized $8.5\,\text{GeV}$ photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson $\rho$(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. We confirm a high degree of $s$-channel helicity conservation at small squared four-momentum transfer $t$ and are able to extract the $t$-dependence of natural and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full $t$ range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced $\rho(770)$ differ by two units are negligible for $-t<0.5\,\text{GeV}^{2}/c^{2}$., Comment: 15 pages, 11 figures
Published: 2023
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8. Measurement of the J/$\psi $ photoproduction cross section over the full near-threshold kinematic region

Author: GlueX Collaboration, Adhikari, S., Afzal, F., Akondi, C. S., Albrecht, M., Amaryan, M., Arroyave, V., Asaturyan, A., Austregesilo, A., Baldwin, Z., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Briscoe, W. J., Britton, T., Brooks, W. K., Byer, D., Chudakov, E., Cole, P. L., Cortes, O., Crede, V., Dalton, M. M., Darulis, D., Deur, A., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Ebersole, D., Egiyan, H., Erbora, T., Eugenio, P., Fabrizi, A., Fanelli, C., Fang, S., Fegan, S., Fitches, J., Foda, A. M., Furletov, S., Gan, L., Gao, H., Gardner, A., Gasparian, A., Gleason, C., Goetzen, K., Goryachev, V. S., Grube, B., Guo, J., Guo, L., Hague, T. J., Hakobyan, H., Hernandez, J., Hoffman, N. D., Hornidge, D., Hou, G., Huber, G. M., Hurck, P., Hurley, A., Imoehl, W., Ireland, D. G., Ito, M. M., Jaegle, I., Jarvis, N. S., Jeske, T., Jones, R. T., Kakoyan, V., Kalicy, G., Khachatryan, V., Khatchatryan, M., Kourkoumelis, C., LaDuke, A., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Li, W. B., Liu, B., Livingston, K., Lolos, G. J., Lorenti, L., Lyubovitskij, V., Mack, D., Mahmood, A., Martel, P. P., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mizutani, K., Neelamana, V., Ng, L., Nissen, E., Orei, S., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Pedroni, R., Pentchev, L., Peters, K. J., Prather, E., Rakshit, S., Reinhold, J., Remington, A., Ritchie, B. G., Ritman, J., Rodriguez, G., Romanov, D., Saldana, K., Salgado, C., Schadmand, S., Schertz, A. M., Scheuer, K., Schick, A., Schmidt, A., Schumacher, R. A., Schwiening, J., Sharp, P., Shen, X., Shepherd, M. R., Smith, A., Smith, E. S., Sober, D. I., Somov, S., Somov, A., Stevens, J. R., Strakovsky, I. I., Sumner, B., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Viducic, T., Whitlatch, T., Wickramaarachchi, N., Williams, M., Wunderlich, Y., Yu, B., Zarling, J., Zhang, Z., Zhao, Z., Zhou, X., Zhou, J., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: We report the total and differential cross sections for $J/\psi$ photoproduction with the large acceptance GlueX spectrometer for photon beam energies from the threshold at 8.2~GeV up to 11.44~GeV and over the full kinematic range of momentum transfer squared, $t$. Such coverage facilitates the extrapolation of the differential cross sections to the forward ($t = 0$) point beyond the physical region. The forward cross section is used by many theoretical models and plays an important role in understanding $J/\psi$ photoproduction and its relation to the $J/\psi-$proton interaction. These measurements of $J/\psi$ photoproduction near threshold are also crucial inputs to theoretical models that are used to study important aspects of the gluon structure of the proton, such as the gluon Generalized Parton Distribution (GPD) of the proton, the mass radius of the proton, and the trace anomaly contribution to the proton mass. We observe possible structures in the total cross section energy dependence and find evidence for contributions beyond gluon exchange in the differential cross section close to threshold, both of which are consistent with contributions from open-charm intermediate states., Comment: 15 pages 18 figures
Published: 2023
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9. The Arches cluster revisited: IV. Observational constraints on the binary properties of very massive stars

Author: Clark, J. S., Lohr, M. E., Najarro, F., Patrick, L. R., and Ritchie, B. W.
Subjects: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract: Serving as the progenitors of electromagnetic and gravitational wave transients, massive stars have received renewed interest in recent years. However, many aspects of their birth and evolution remain opaque, particularly in the context of binary interactions. The centre of our galaxy hosts a rich cohort of very massive stars, which appear to play a prominent role in the ecology of the region. In this paper we investigate the binary properties of the Arches cluster, which is thought to host a large number of very massive stars. A combination of multi-epoch near-IR spectroscopy and photometry was utilised to identify binaries. 13 from 36 cluster members meet our criteria to be classed as RV variable. Combining the spectroscopic data with archival radio and X-ray observations - to detect colliding wind systems - provides a lower limit to the binary fraction of ~43%; increasing to >50% for the O-type hypergiants and WNLha. Dynamical and evolutionary masses reveal the primaries to be uniformly massive (>50M$_{\odot}$). Where available, orbital analysis reveals a number of short period, highly eccentric binaries, which appear to be pre-interaction systems. Such systems are X-ray luminous, with 80% above an empirical bound of $(L_{\rm x}/L_{\rm bol})\sim10^{-7}$ and their orbital configurations suggest formation and evolution via a single star channel; however, we cannot exclude a binary formation channel for a subset. Qualitative comparison to surveys of lower mass OB-type stars confirms that the trend to an extreme binary fraction (>60%) extends to the most massive stars currently forming in the local Universe., Comment: Accepted in MNRAS; In Memoriam: This work is dedicated to the memory of our dearest friend and colleague Simon Clark
Published: 2023
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10. CORE -- a COmpact detectoR for the EIC

Author: CORE Collaboration, Alarcon, R., Baker, M., Baturin, V., Brindza, P., Bueltmann, S., Bukhari, M., Capobianco, R., Christy, E., Diehl, S., Dugger, M., Dupré, R., Dzhygadlo, R., Flood, K., Gnanvo, K., Guo, L., Hayward, T., Hattawy, M., Hoballah, M., Hohlmann, M., Hyde, C. E., Ilieva, Y., Jacobs, W. W., Joo, K., Kalicy, G., Kim, A., Kubarovsky, V., Lehmann, A., Li, W., Marchand, D., Marukyan, H., Murray, M. J., Montgomery, H. E., Morozov, V., Mostafanezhad, I., Movsisyan, A., Munevar, E., Camacho, C. Muñoz, Nadel-Turonski, P., Niccolai, S., Peters, K., Prokudin, A., Richards, J., Ritchie, B. G., Shrestha, U., Schmookler, B., Schnell, G., Schwarz, C., Schwiening, J., Schweitzer, P., Simmerling, P., Szumila-Vance, H., Tripathi, S., Trotta, N., Varner, G., Vossen, A., Voutier, E., Wickramaarachchi, N., and Zachariou, N.
Subjects: Physics - Instrumentation and Detectors, Nuclear Experiment
Abstract: The COmpact detectoR for the Eic (CORE) Proposal was submitted to the EIC "Call for Collaboration Proposals for Detectors". CORE comprehensively covers the physics scope of the EIC Community White Paper and the National Academies of Science 2018 report. The design exploits advances in detector precision and granularity to minimize size. The central detector includes a 3Tesla, 2.5m solenoid. Tracking is primarily silicon. Electromagnetic calorimetry is based on the high performance crystals. Ring-imaging Cherenkov detectors provide hadronic particle identification., Comment: Contact authors: C.E. Hyde, chyde@odu.edu and P. Nadel-Turonski, turonski@jlab.org
Published: 2022

11. A VLT/FLAMES survey for massive binaries in Westerlund 1: VIII. Binary Systems and Orbital Parameters

Author: Ritchie, B. W., Clark, J. S., Negueruela, I., and Najarro, F.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: The galactic cluster Westerlund 1 contains a rich population of evolved, massive stars, and a high binary fraction has been inferred from previous multiwavelength observations. We use multi-epoch spectroscopy of a large sample of early-type stars to identify new binaries and binary candidates in the cluster. VLT/FLAMES was used to obtain spectra of ~100 OB stars over a 14-month baseline in 2008 and 2009, supplemented with follow-up observations in 2011 and 2013, and we identify 20 new OB I--III binaries, a WN9h binary, and a WC9d binary, greatly increasing the number of directly confirmed binary systems in Westerlund 1, while 12 O9--9.5 Iab--III stars are identified as candidate binaries. The 173.9 day SB1 W1030 represents the first longer-period system identified in the cluster, while the determination of a 53.95 day period for W44/L makes it the first Wolf-Rayet binary in Westerlund 1 with a confirmed orbital period greater than ten days. Our results suggest the binary fraction in the OB population is at least 40%, and may be significantly higher. (Abridged), Comment: Accepted for publication in Astronomy & Astrophysics, and dedicated to the memory of Dr Simon Clark
Published: 2021
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12. Search for photoproduction of axion-like particles at GlueX

Author: GlueX Collaboration, Adhikari, S., Akondi, C. S., Albrecht, M., Ali, A., Amaryan, M., Asaturyan, A., Austregesilo, A., Baldwin, Z., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Briscoe, W. J., Britton, T., Brooks, W. K., Chudakov, E., Cole, S., Cole, P. L., Cortes, O., Crede, V., Dalton, M. M., Deur, A., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Ebersole, D., Egiyan, H., Erbora, T., Ernst, A., Eugenio, P., Fanelli, C., Fegan, S., Fitches, J., Foda, A. M., Furletov, S., Gan, L., Gao, H., Gasparian, A., Gleason, C., Goetzen, K., Goryachev, V. S., Guo, L., Hagen, M., Hakobyan, H., Hamdi, A., Hernandez, J., Hoffman, N. D., Hou, G., Huber, G. M., Hurley, A., Ireland, D. G., Ito, M. M., Jaegle, I., Jarvis, N. S., Jones, R. T., Kakoyan, V., Kalicy, G., Kamel, M., Khachatryan, V., Khatchatryan, M., Kourkoumelis, C., Kuleshov, S., LaDuke, A., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Li, W. B., Liu, B., Livingston, K., Lolos, G. J., Lorenti, L., Luckas, K., Lyubovitskij, V., Mack, D., Mahmood, A., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mizutani, K., Neelamana, V., Nerling, F., Ng, L., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Pauli, P., Pedroni, R., Pentchev, L., Peters, K. J., Reinhold, J., Ritchie, B. G., Ritman, J., Rodriguez, G., Romanov, D., Romero, C., Saldana, K., Salgado, C., Schadmand, S., Schertz, A. M., Schick, A., Schmidt, A., Schumacher, R. A., Schwiening, J., Sharp, P., Shen, X., Shepherd, M. R., Smith, A., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Stevens, J. R., Strakovsky, I. I., Sumner, B., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Vasileiadis, G., Viducic, T., Whitlatch, T., Wickramaarachchi, N., Williams, M., Yang, Y., Yoon, S., Zarling, J., Zhang, Z., Zhao, Z., Zhou, J., Zhou, X., and Zihlmann, B.
Subjects: High Energy Physics - Experiment, Nuclear Experiment
Abstract: We present a search for axion-like particles, $a$, produced in photon-proton collisions at a center-of-mass energy of approximately 4 GeV, focusing on the scenario where the $a$-gluon coupling is dominant. The search uses $a\to\gamma\gamma$ and $a\to\pi^+\pi^-\pi^0$ decays, and a data sample corresponding to an integrated luminosity of 168 pb$^{-1}$ collected with the GlueX detector. The search for $a\to\gamma\gamma$ decays is performed in the mass range of $180 < m_a < 480$ MeV, while the search for $a\to\pi^+\pi^-\pi^0$ decays explores the $600 < m_a < 720$ MeV region. No evidence for a signal is found, and 90% confidence-level exclusion limits are placed on the $a$-gluon coupling strength. These constraints are the most stringent to date over much of the mass ranges considered., Comment: 8 pages, 4 figures, 2 tables; updated to published version
Published: 2021
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13. Measurement of Spin Density Matrix Elements in $\Lambda(1520)$ Photoproduction at 8.2-8.8 GeV

Author: GlueX Collaboration, Adhikari, S., Akondi, C. S., Albrecht, M., Ali, A., Amaryan, M., Asaturyan, A., Austregesilo, A., Baldwin, Z., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Briscoe, W. J., Britton, T., Brooks, W. K., Chudakov, E., Cole, S., Cole, P. L., Cortes, O., Crede, V., Dalton, M. M., Daniels, T., Deur, A., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Egiyan, H., Erbora, T., Ernst, A., Eugenio, P., Fanelli, C., Fegan, S., Fitches, J., Foda, A. M., Furletov, S., Gan, L., Gao, H., Gasparian, A., Gleason, C., Goetzen, K., Goryachev, V. S., Guo, L., Hagen, M., Hakobyan, H., Hamdi, A., Hernandez, J., Hoffman, N. D., Hou, G., Huber, G. M., Hurley, A., Ireland, D. G., Ito, M. M., Jaegle, I., Jarvis, N. S., Jones, R. T., Kakoyan, V., Kalicy, G., Kamel, M., Khachatryan, V., Khatchatryan, M., Kourkoumelis, C., Kuleshov, S., LaDuke, A., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Li, W. B., Liu, B., Livingston, K., Lolos, G. J., Luckas, K., Lyubovitskij, V., Mack, D., Mahmood, A., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mizutani, K., Neelamana, V., Nerling, F., Ng, L., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Pauli, P., Pedroni, R., Pentchev, L., Peters, K. J., Reinhold, J., Ritchie, B. G., Ritman, J., Rodriguez, G., Romanov, D., Romero, C., Saldana, K., Salgado, C., Schadmand, S., Schertz, A. M., Schick, A., Schmidt, A., Schumacher, R. A., Schwiening, J., Sharp, P., Shen, X., Shepherd, M. R., Smith, A., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Stevens, J. R., Strakovsky, I. I., Sumner, B., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Vasileiadis, G., Viducic, T., Whitlatch, T., Wickramaarachchi, N., Williams, M., Yang, Y., Zarling, J., Zhang, Z., Zhao, Z., Zhou, J., Zhou, X., Zhou, Q., Zihlmann, B., Glazier, D. I., and Mathieu, V.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: We report on the measurement of spin density matrix elements of the $\Lambda(1520)$ in the photoproduction reaction $\gamma p\rightarrow \Lambda(1520)K^+$, via its subsequent decay to $K^{-}p$. The measurement was performed as part of the GlueX experimental program in Hall D at Jefferson Lab using a linearly polarized photon beam with $E_\gamma =$ 8.2-8.8 GeV. These are the first such measurements in this photon energy range. Results are presented in bins of momentum transfer squared, $-(t-t_\text{0})$. We compare the results with a Reggeon exchange model and determine that natural exchange amplitudes are dominant in $\Lambda(1520)$ photoproduction., Comment: 11 pages, 8 figures, accepted version
Published: 2021
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14. Photoproduction of the $f_2(1270)$ meson using the CLAS detector

Author: Carver, M., Celentano, A., Hicks, K., Marsicano, L., Mathieu, V., Pilloni, A., Adhikari, K. P., Adhikari, S., Amaryan, M. J., Angelini, Giovanni, Atac, H., Baltzell, N. A., Barion, L., Battaglieri, M., Bedlinskiy, I., Benmokhtar, Fatiha, Bianconi, A., Biselli, A. S., Bondi, M., Bossù, F., Boiarinov, S., Briscoe, W. J., Brooks, W. K., Bulumulla, D., Burkert, V. D., Carman, D. S., Carvajal, J. C., Chatagnon, P., Chetry, T., Ciullo, G., Clark, L., Clary, B. A., Cole, P. L., Contalbrigo, M., Crede, V., D'Angelo, A., Dashyan, N., De~Vita, R., Defurne, M., Deur, A., Diehl, S., Djalali, C., Dugger, M., Dupre, R., Egiyan, H., Ehrhart, M., El~Alaoui, A., El~Fassi, L., Eugenio, P., Fedotov, G., Fegan, S., Filippi, A., Gavalian, G., Gevorgyan, N., Gilfoyle, G. P., Girod, F. X., Gothe, R. W., Griffioen, K. A., Hafidi, K., Hakobyan, H., Hattawy, M., Hayward, T. B., Heddle, D., Holtrop, M., Huang, Q., Hyde, C. E., Ilieva, Y., Ireland, D. G., Isupov, E. L., Jenkins, D., Jo, H. S., Joo, K., Joosten, S. ~, Keller, D., Khanal, A., Khandaker, M., Kim, A., Kim, C. W., Klein, F. J., Kripko, A., Kubarovsky, V., Lanza, L., Leali, M., Lenisa, P., Livingston, K., MacGregor, I. J. D., Marchand, D., Mascagna, V., McCracken, M. E., McKinnon, B., Meziani, Z. E., Mokeev, V., A~Movsisyan, Munevar, E., Munoz~Camacho, C., Nadel-Turonski, P., Neupane, K., Niccolai, S., Niculescu, G., Osipenko, M., Ostrovidov, A. I., Paolone, M., Pappalardo, L. L., Paremuzyan, R., Pasyuk, E., Phelps, W., Pogorelko, O., Prok, Y., Protopopescu, D., Ripani, M., Ritchie, B. G., Ritman, J., Rizzo, A., Rosner, G., Rowley, J., Sabatié, F., Salgado, C., Schmidt, A., Schumacher, R. A., Sharabian, Y. G., Shrestha, U., Sokhan, D., Soto, O., Sparveris, N., Stepanyan, S., Strakovsky, I. I., Strauch, S., Tyler, N., Tyson, R., Ungaro, M., Venturelli, L., Voskanyan, H., Voutier, E., Watts, D. P., Wei, K., Wei, X., Yale, B., Zachariou, N., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: The quark structure of the $f_2(1270)$ meson has, for many years, been assumed to be a pure quark-antiquark ($q\bar{q}$) resonance with quantum numbers $J^{PC} = 2^{++}$. Recently, it was proposed that the $f_2(1270)$ is a molecular state made from the attractive interaction of two $\rho$-mesons. Such a state would be expected to decay strongly to final states with charged pions, due to the dominant decay $\rho \to \pi^+ \pi^-$, whereas decay to two neutral pions would likely be suppressed. Here, we measure for the first time the reaction $\gamma p \to \pi^0 \pi^0 p$, using the CLAS detector at Jefferson Lab for incident beam energies between 3.6-5.4~GeV. Differential cross sections, $d\sigma / dt$, for $f_2(1270)$ photoproduction are extracted with good precision, due to low backgrounds, and are compared with theoretical calculations., Comment: 5 pages, 4 figures
Published: 2020
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15. Measurement of beam asymmetry for $\pi^-\Delta^{++}$ photoproduction on the proton at $E_\gamma$=8.5 GeV

Author: GlueX Collaboration, Adhikari, S., Akondi, C. S., Ali, A., Amaryan, M., Asaturyan, A., Austregesilo, A., Baldwin, Z., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Briscoe, W. J., Britton, T., Brooks, W. K., Cannon, B. E., Chudakov, E., Cole, S., Cortes, O., Crede, V., Dalton, M. M., Daniels, T., Deur, A., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Egiyan, H., Erbora, T., Ernst, A., Eugenio, P., Fanelli, C., Fegan, S., Fitches, J., Foda, A. M., Furletov, S., Gan, L., Gao, H., Gasparian, A., Gleason, C., Goetzen, K., Goryachev, V. S., Guo, L., Hakobyan, H., Hamdi, A., Huber, G. M., Hurley, A., Ireland, D. G., Ito, M. M., Jaegle, I., Jarvis, N. S., Jones, R. T., Kakoyan, V., Kalicy, G., Kamel, M., Khachatryan, V., Khatchatryan, M., Kourkoumelis, C., Kuleshov, S., LaDuke, A., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Li, W. B., Liu, B., Livingston, K., Lolos, G. J., Luckas, K., Lyubovitskij, V., Mack, D., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., McGinley, W., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mizutani, K., Neelamana, V., Nerling, F., Ng, L., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Pauli, P., Pedroni, R., Pentchev, L., Peters, K. J., Phelps, W., Pooser, E., Reinhold, J., Ritchie, B. G., Ritman, J., Rodriguez, G., Romanov, D., Romero, C., Salgado, C., Schadmand, S., Schertz, A. M., Schick, A., Schumacher, R. A., Schwiening, J., Shen, X., Shepherd, M. R., Smith, A., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Stevens, J. R., Strakovsky, I. I., Sumner, B., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Vasileiadis, G., Whitlatch, T., Wickramaarachchi, N., Williams, M., Yang, Y., Zarling, J., Zhang, Z., Zhao, Z., Zhou, J., Zhou, Q., Zhou, X., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: We report a measurement of the $\pi^-$ photoproduction beam asymmetry for the reaction $\vec{\gamma} p \rightarrow \pi^- \Delta^{++}$ using data from the GlueX experiment in the photon beam energy range 8.2--8.8 GeV. The asymmetry $\Sigma$ is measured as a function of four-momentum transfer $t$ to the $\Delta^{++}$ and compared to phenomenological models. We find that $\Sigma$ varies as a function of $t$: negative at smaller values and positive at higher values of $|t|$. The reaction can be described theoretically by $t$-channel particle exchange requiring pseudoscalar, vector, and tensor intermediaries. In particular, this reaction requires charge exchange, allowing us to probe pion exchange and the significance of higher-order corrections to one-pion exchange at low momentum transfer. Constraining production mechanisms of conventional mesons may aid in the search for and study of unconventional mesons. This is the first measurement of the process at this energy., Comment: 7 pages, 5 figures
Published: 2020
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16. The GlueX Beamline and Detector

Author: Adhikari, S., Akondi, C. S., Ghoul, H. Al, Ali, A., Amaryan, M., Anassontzis, E. G., Austregesilo, A., Barbosa, F., Barlow, J., Barnes, A., Barriga, E., Barsotti, R., Beattie, T. D., Benesch, J., Berdnikov, V. V., Biallas, G., Black, T., Boeglin, W., Brindza, P., Briscoe, W. J., Britton, T., Brock, J., Brooks, W. K., Cannon, B. E., Carlin, C., Carman, D. S., Carstens, T., Cao, N., Chernyshov, O., Chudakov, E., Cole, S., Cortes, O., Crahen, W. D., Crede, V., Dalton, M. M., Daniels, T., Deur, A., Dickover, C., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Dzierba, A., Egiyan, H., Erbora, T., Ernst, A., Eugenio, P., Fanelli, C., Fegan, S., Foda, A. M., Foote, J., Frye, J., Furletov, S., Gan, L., Gasparian, A., Gerasimov, A., Gevorgyan, N., Gleason, C., Goetzen, K., Goryachev, A. Goncalves V. S., Guo, L., Hakobyan, H., Hamdi, A., Hardin, J., Henschel, C. L., Huber, G. M., Hutton, C., Hurley, A., Ioannou, P., Ireland, D. G., Ito, M. M., Jarvis, N. S., Jones, R. T., Kakoyan, V., Katsaganis, S., Kalicy, G., Kamel, M., Keith, C. D., Klein, F. J., Kliemt, R., Kolybaba, D., Kourkoumelis, C., Krueger, S. T., Kuleshov, S., Larin, I., Lawrence, D., Leckey, J. P., Lersch, D. I., Leverington, B. D., Levine, W. I., Li, W., Liu, B., Livingston, K., Lolos, G. J., Lyubovitskij, V., Mack, D., Marukyan, H., Mattione, P. T., Matveev, V., McCaughan, M., McCracken, M., McGinley, W., McIntyre, J., Meekins, D., Mendez, R., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mokaya, F., Moriya, K., Nerling, F., Ng, L., Ni, H., Ostrovidov, A. I., Papandreou, Z., Patsyuk, M., Paudel, C., Pauli, P., Pedroni, R., Pentchev, L., Peters, K. J., Phelps, W., Pierce, J., Pooser, E., Popov, V., Pratt, B., Qiang, Y., Qin, N., Razmyslovich, V., Reinhold, J., Ritchie, B. G., Ritman, J., Robison, L., Romanov, D., Romero, C., Salgado, C., Sandoval, N., Satogata, T., Schertz, A. M., Schadmand, S., Schick, A., Schumacher, R. A., Schwarz, C., Schwiening, J., Semenov, A. Yu., Semenova, I. A., Seth, K. K., Shen, X., Shepherd, M. R., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Sparks, N., Staib, M. J., Stanislav, C., Stevens, J. R., Stewart, J., Strakovsky, I. I., Summner, B. C. L., Suresh, K., Tarasov, V. V., Taylor, S., Teigrob, L. A., Teymurazyan, A., Thiel, A., Tolstukhin, I., Tomaradze, A., Toro, A., Tsaris, A., Van Haarlem, Y., Vasileiadis, G., Vega, I., Visser, G., Voulgaris, G., Walford, N. K., Werthmüller, D., Whitlatch, T., Wickramaarachchi, N., Williams, M., Wolin, E., Xiao, T., Yang, Y., Zarling, J., Zhang, Z., Zhou, Q., Zhou, X., and Zihlmann, B.
Subjects: Physics - Instrumentation and Detectors, Nuclear Experiment
Abstract: The GlueX experiment at Jefferson Lab has been designed to study photoproduction reactions with a 9-GeV linearly polarized photon beam. The energy and arrival time of beam photons are tagged using a scintillator hodoscope and a scintillating fiber array. The photon flux is determined using a pair spectrometer, while the linear polarization of the photon beam is determined using a polarimeter based on triplet photoproduction. Charged-particle tracks from interactions in the central target are analyzed in a solenoidal field using a central straw-tube drift chamber and six packages of planar chambers with cathode strips and drift wires. Electromagnetic showers are reconstructed in a cylindrical scintillating fiber calorimeter inside the magnet and a lead-glass array downstream. Charged particle identification is achieved by measuring energy loss in the wire chambers and using the flight time of particles between the target and detectors outside the magnet. The signals from all detectors are recorded with flash ADCs and/or pipeline TDCs into memories allowing trigger decisions with a latency of 3.3 $\mu$s. The detector operates routinely at trigger rates of 40 kHz and data rates of 600 megabytes per second. We describe the photon beam, the GlueX detector components, electronics, data-acquisition and monitoring systems, and the performance of the experiment during the first three years of operation., Comment: Accepted by Nuclear Instruments and Methods A, 78 pages, 54 figures
Published: 2020
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17. Measurement of the Photon Beam Asymmetry in $\vec{\gamma} p\to K^+\Sigma^0$ at $E_{\gamma} = 8.5$ GeV

Author: The GlueX Collaboration, Adhikari, S., Ali, A., Amaryan, M., Austregesilo, A., Barbosa, F., Barlow, J., Barriga, E., Barsotti, R., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Briscoe, W. J., Britton, T., Brooks, W. K., Cannon, B. E., Cao, N., Chudakov, E., Cole, S., Cortes, O., Crede, V., Dalton, M. M., Daniels, T., Deur, A., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Egiyan, H., Erbora, T., Ernst, A., Eugenio, P., Fanelli, C., Fegan, S., Foda, A. M., Foote, J., Frye, J., Furletov, S., Gan, L., Gasparian, A., Gleason, C., Goetzen, K., Goncalves, A., Goryachev, V. S., Guo, L., Hakobyan, H., Hamdi, A., Huber, G. M., Hurley, A., Ireland, D. G., Ito, M. M., Jarvis, N. S., Jones, R. T., Kakoyan, V., Kalicy, G., Kamel, M., Kourkoumelis, C., Kuleshov, S., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Li, W., Liu, B., Livingston, K., Lolos, G. J., Lyubovitskij, V., Mack, D., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., McGinley, W., Meyer, C. A., Miskimen, R., Mitchell, R. E., Nerling, F., Ng, L., Ni, H., Ostrovidov, A. I., Papandreou, Z., Patsyuk, M., Paudel, C., Pauli, P., Pedroni, R., Pentchev, L., Peters, K. J., Phelps, W., Pooser, E., Qin, N., Reinhold, J., Ritchie, B. G., Robison, L., Romanov, D., Romero, C., Salgado, C., Schertz, A. M., Schumacher, R. A., Schwiening, J., Seth, K. K., Shen, X., Shepherd, M. R., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Stevens, J. R., Strakovsky, I. I., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Vasileiadis, G., Whitlatch, T., Wickramaarachchi, N., Williams, M., Xiao, T., Yang, Y., Zarling, J., Zhang, Z., Zhou, Q., Zhou, X., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract: We report measurements of the photon beam asymmetry $\Sigma$ for the reaction $\vec{\gamma} p\to K^+\Sigma^0$(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected using a linearly polarized photon beam in the energy range of 8.2-8.8 GeV incident on a liquid hydrogen target. The beam asymmetry $\Sigma$ was measured as a function of the Mandelstam variable $t$, and a single value of $\Sigma$ was extracted for events produced in the $u$-channel. These are the first exclusive measurements of the photon beam asymmetry $\Sigma$ for the reaction in this energy range. For the $t$-channel, the measured beam asymmetry is close to unity over the $t$-range studied, $-t=(0.1-1.4)~$(GeV/$c$)$^{2}$, with an average value of $\Sigma = 1.00\pm 0.05$. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the $K^{*}$(892) Regge trajectory. A value of $\Sigma = 0.41 \pm 0.09$ is obtained for the $u$-channel integrated up to $-u=2.0$~(GeV/$c$)$^{2}$.
Published: 2020
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18. A VLT/FLAMES survey for massive binaries in Westerlund 1: VII. Cluster census

Author: Clark, J. S., Ritchie, B. W., and Negueruela, I.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: The formation, properties, and evolution of massive stars remain subject to considerable uncertainty; impacting on fields as diverse as galactic feedback and the nature of the progenitors of both electromagnetic and gravitational wave transients. The clusters many such stars reside within provide a unique laboratory for addressing these issues, and in this work we provide a comprehensive stellar census of Westerlund 1 to underpin such efforts. 69 new members were identified via I-band spectroscopy, yielding a total cluster population of 166 stars with initial masses of ~25Msun to ~50Msun, with more massive stars already lost to supernova. The stellar population follows a smooth and continuous morphological sequence from late-O giant through to OB supergiant. Subsequently, the progression bifurcates, with one branch yielding mid- to late-B hypergiants and cool super-/hypergiants, and the other massive blue stragglers, prior to a diverse population of H-depleted Wolf-Rayets. A substantial population of O-type stars with anomalously broad Paschen series lines are seen, a property which we attribute to binarity. Binary interaction is clearly required to yield the uniquely rich cohort of hypergiants, which includes both mass-stripped primaries and rejuvenated secondaries/stellar mergers. As a consequence future observations of Wd1 and similar stellar aggregates hold out the prospect of characterising both single- and binary- evolutionary channels for massive stars and determining their relative contributions. This in turn will permit the physical properties of such objects at the point of core-collapse to be predicted; of direct relevance for understanding the formation of relativistic remnants such as the magnetars associated with Wd1 and other young massive clusters (Abridged)., Comment: 21 pages, 9 figures, accepted for publication in Astronomy and Astrophysics
Published: 2019
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19. Beam Asymmetry $\mathbf{\Sigma}$ for the Photoproduction of $\mathbf{\eta}$ and $\mathbf{\eta^{\prime}}$ Mesons at $\mathbf{E_{\gamma}=8.8}$GeV

Author: The GlueX Collaboration, Adhikari, S., Ali, A., Amaryan, M., Austregesilo, A., Barbosa, F., Barlow, J., Barnes, A., Barriga, E., Barsotti, R., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Boer, M., Briscoe, W. J., Britton, T., Brooks, W. K., Cannon, B. E., Cao, N., Chudakov, E., Cole, S., Cortes, O., Crede, V., Dalton, M. M., Daniels, T., Deur, A., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Egiyan, H., Erbora, T., Ernst, A., Eugenio, P., Fanelli, C., Fegan, S., Foda, A. M., Foote, J., Frye, J., Furletov, S., Gan, L., Gasparian, A., Gevorgyan, N., Gleason, C., Goetzen, K., Goncalves, A., Goryachev, V. S., Guo, L., Hakobyan, H., Hamdi, A., Huber, G. M., Hurley, A., Ireland, D. G., Ito, M. M., Jarvis, N. S., Jones, R. T., Kakoyan, V., Kalicy, G., Kamel, M., Kourkoumelis, C., Kuleshov, S., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Li, W., Liu, B., Livingston, K., Lolos, G. J., Lyubovitskij, V., Mack, D., Marukyan, H., Mattione, P., Matveev, V., McCaughan, M., McCracken, M., McGinley, W., Meyer, C. A., Miskimen, R., Mitchell, R. E., Nerling, F., Ng, L., Ostrovidov, A. I., Papandreou, Z., Patsyuk, M., Paudel, C., Pauli, P., Pedroni, R., Pentchev, L., Peters, K. J., Phelps, W., Pooser, E., Qin, N., Reinhold, J., Ritchie, B. G., Robison, L., Romanov, D., Romero, C., Salgado, C., Schertz, A. M., Schumacher, R. A., Schwiening, J., Semenov, A. Yu., Semenova, I. A., Seth, K. K., Shen, X., Shepherd, M. R., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Staib, M., Stevens, J. R., Strakovsky, I. I., Suresh, K., Tarasov, V. V., Taylor, S., Teymurazyan, A., Thiel, A., Vasileiadis, G., Whitlatch, T., Wickramaarachchi, N., Williams, M., Xiao, T., Yang, Y., Zarling, J., Zhang, Z., Zhao, G., Zhou, Q., Zhou, X., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: We report on the measurement of the beam asymmetry $\Sigma$ for the reactions $\vec{\gamma}p\rightarrow p\eta$ and $\vec{\gamma}p \rightarrow p\eta^{\prime}$ from the GlueX experiment, using an 8.2--8.8 GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Lab. These measurements are made as a function of momentum transfer $-t$, with significantly higher statistical precision than our earlier $\eta$ measurements, and are the first measurements of $\eta^{\prime}$ in this energy range. We compare the results to theoretical predictions based on $t$--channel quasi-particle exchange. We also compare the ratio of $\Sigma_{\eta}$ to $\Sigma_{\eta^{\prime}}$ to these models, as this ratio is predicted to be sensitive to the amount of $s\bar{s}$ exchange in the production. We find that photoproduction of both $\eta$ and $\eta^{\prime}$ is dominated by natural parity exchange with little dependence on $-t$., Comment: 18 pages, 7 figures
Published: 2019
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20. First measurement of near-threshold J/$\psi $ exclusive photoproduction off the proton

Author: The GlueX Collaboration, Ali, A., Amaryan, M., Anassontzis, E. G., Austregesilo, A., Baalouch, M., Barbosa, F., Barlow, J., Barnes, A., Barriga, E., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Boer, M., Briscoe, W. J., Britton, T., Brooks, W. K., Cannon, B. E., Cao, N., Chudakov, E., Cole, S., Cortes, O., Crede, V., Dalton, M. M., Daniels, T., Deur, A., Dobbs, S., Dolgolenko, A., Dotel, R., Dugger, M., Dzhygadlo, R., Egiyan, H., Ernst, A., Eugenio, P., Fanelli, C., Fegan, S., Foda, A. M., Foote, J., Frye, J., Furletov, S., Gan, L., Gasparian, A., Gauzshtein, V., Gevorgyan, N., Gleason, C., Goetzen, K., Goncalves, A., Goryachev, V. S., Guo, L., Hakobyan, H., Hamdi, A., Han, S., Hardin, J., Huber, G. M., Hurley, A., Ireland, D. G., Ito, M. M., Jarvis, N. S., Jones, R. T., Kakoyan, V., Kalicy, G., Kamel, M., Kourkoumelis, C., Kuleshov, S., Kuznetsov, I., Larin, I., Lawrence, D., Lersch, D. I., Li, H., Li, W., Liu, B., Livingston, K., Lolos, G. J., Lyubovitskij, V., Mack, D., Marukyan, H., Matveev, V., McCaughan, M., McCracken, M., McGinley, W., McIntyre, J., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mokaya, F., Nerling, F., Ng, L., Ostrovidov, A. I., Papandreou, Z., Patsyuk, M., Pauli, P., Pedroni, R., Pentchev, L., Peters, K. J., Phelps, W., Pooser, E., Qin, N., Reinhold, J., Ritchie, B. G., Robison, L., Romanov, D., Romero, C., Salgado, C., Schertz, A. M., Schumacher, R. A., Schwiening, J., Seth, K. K., Shen, X., Shepherd, M. R., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Stevens, J. R., Strakovsky, I. I., Suresh, K., Tarasov, V., Taylor, S., Teymurazyan, A., Thiel, A., Vasileiadis, G., Werthmueller, D., Whitlatch, T., Wickramaarachchi, N., Williams, M., Xiao, T., Yang, Y., Zarling, J., Zhang, Z., Zhao, G., Zhou, Q., Zhou, X., and Zihlmann, B.
Subjects: Nuclear Experiment
Abstract: We report on the measurement of the $\gamma p \rightarrow J/\psi p$ cross section from $E_\gamma = 11.8$ GeV down to the threshold at $8.2$ GeV using a tagged photon beam with the GlueX experiment. We find the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section $d\sigma /dt$ has an exponential slope of $1.67 \pm 0.39$ GeV$^{-2}$ at $10.7$ GeV average energy. The LHCb pentaquark candidates $P_c^+$ can be produced in the $s$-channel of this reaction. We see no evidence for them and set model-dependent upper limits on their branching fractions $\mathcal{B}(P_c^+ \rightarrow J/\psi p)$ and cross sections $\sigma(\gamma p \to P_c^+)\times\mathcal{B}(P_c^+ \to J/\psi p) $., Comment: 12 pages, 7 figures
Published: 2019
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21. High Precision Measurement of Compton Scattering in the 5 GeV region

Author: Ambrozewicz, P., Ye, L., Prok, Y., Larin, I., Ahmidouch, A., Baker, K., Baturin, V., Benton, L., Bernstein, A., Burkert, V., Clinton, E., Cole, P. L., Collins, P., Dale, D., Danagoulian, S., Davidenko, G., Demirchyan, R., Deur, A., Dolgolenko, A., Dutta, D., Dzyubenko, G., Evdokimov, A., Fedotov, G., Feng, J., Gabrielyan, M., Gan, L., Gao, H., Gasparian, A., Gevorkyan, N., Gevorkyan, S., Glamazdin, A., Goryachev, V., Guo, L., Gyurjyan, V., Hardy, K., He, J., Isupov, E., Ito, M., Jiang, L., Kang, H., Kashy, D., Khandaker, M., Kingsberry, P., Klein, F., Kolarkar, A., Konchatnyi, M., Korchin, O., Korsch, W., Kosinov, O., Kowalski, S., Kubantsev, M., Kubarovsky, A., Kubarovsky, V., Lawrence, D., Li, X., Levillain, M., Lu, H., Ma, L., Martel, P., Matveev, V., McNulty, D., Mecking, B., Micherdzinska, A., Milbrath, B., Minehart, R., Miskimen, R., Mochalov, V., Morrison, B., Mtingwa, S., Nakagawa, I., Overby, S., Pasyuk, E., Payen, M., Park, K., Pedroni, R, Phelps, W., Protopopescu, D., Rimal, D., Ritchie, B. G., Romanov, D., Salgado, C, Shahinyan, A., Sitnikov, A, Sober, D., Stepanyan, S., Stephens, W., Tarasov, V., Taylor, S., Teymurazyan, A., Underwood, J., Vasiliev, A., Vishnyakov, V., Weygand, D. P., Wood, M., Zhang, Y., Zhou, S., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Phenomenology, Nuclear Theory
Abstract: The cross section of atomic electron Compton scattering $\gamma + e \rightarrow \gamma^\prime + e^\prime $ was measured in the 4.40--5.475 GeV photon beam energy region by the {\em PrimEx} collaboration at Jefferson Lab with an accuracy of 2\% and less. The results are consistent with theoretical predictions that include next-to-leading order radiative corrections. The measurements provide the first high precision test of this elementary QED process at beam energies greater than 0.1 GeV., Comment: 6 pages, 4 figures
Published: 2019
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22. Measurement of the helicity asymmetry Eγ→p→→pπ0 for the Eγ→p→→pπ0 reaction in the resonance region: The CLAS Collaboration

Author: Kim, C. W., Zachariou, N., Bashkanov, M., Briscoe, W. J., Fegan, S., Kashevarov, V. L., Nikonov, K., Sarantsev, A., Schmidt, A., Strakovsky, I. I., Watts, D. P., Workman, R. L., Achenbach, P., Akbar, Z., Amaryan, M. J., Angelini, G., Armstrong, W. R., Atac, H., Baashen, L., Baltzell, N. A., Barion, L., Battaglieri, M., Bedlinskiy, I., Benkel, B., Benmokhtar, F., Benmouna, N., Bianconi, A., Biselli, A. S., Booth, W. A., Bossù, F., Boiarinov, S., Brinkmann, K. T., Brock, J., Bulumulla, D., Burkert, V. D., Cao, T., Carlin, C., Carman, D. S., Carvajal, J. C., Chatagnon, P., Chesnokov, V., Chetry, T., Ciullo, G., Clash, G., Cole, P. L., Contalbrigo, M., Becerra, O. Cortes, Costantini, G., Crede, V., D’Angelo, A., Dashyan, N., De Vita, R., Defurne, M., Deur, A., Diehl, S., Djalali, C., Dugger, M., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Elouadrhiri, L., Eugenio, P., Filippi, A., Fogler, C., Gavalian, G., Gilfoyle, G. P., Golubenko, A. A., Gosta, G., Gothe, R. W., Griffioen, K. A., Hafidi, K., Hakobyan, H., Hattawy, M., Hauenstein, F., Hayward, T. B., Heddle, D., Hobart, A., Holtrop, M., Ilieva, Y., Illari, I., Ireland, D. G., Isupov, E. L., Iwamoto, H., Jenkins, D., Jo, H. S., Johnston, R., Joo, K., Joosten, S., Kageya, T., Keith, C. D., Keller, D., Khanal, A., Kim, A., Kim, W., Klein, F. J., Klimenko, V., Kripko, A., Kubarovsky, V., Lanza, L., Leali, M., Lee, S., Li, X., Livingston, K., MacGregor, I. J. D., Marchand, D., Mascagna, V., McKinnon, B., Migliorati, S., Milner, R. G., Mineeva, T., Mokeev, V., Camacho, C. Munoz, Nadel-Turonski, P., Neupane, K., Niccolai, S., Osipenko, M., Ostrovidov, A. I., Pandey, P., Paolone, M., Pappalardo, L. L., Paremuzyan, R., Pasyuk, E., Paul, S. J., Pilleux, N., Pokhrel, M., Poudel, J., Price, J. W., Prok, Y., Radic, A., Ramasubramanian, N., Ratliff, S., Reed, T., Richards, J., Ripani, M., Ritchie, B. G., Ritman, J., Rosner, G., Salgado, C., Schadmand, S., Schott, D., Schumacher, R. A., Scott, M. B. C., Seely, M. L., Seroka, E. M., Shirokov, E. V., Shrestha, U., Sokhan, D., Sparveris, N., Spreafico, M., Strauch, S., Tan, J., Tyson, R., Ungaro, M., Vallarino, S., Venturelli, L., Voskanyan, H., Voutier, E., Wei, X., Williams, R., Wishart, R., Wood, M. H., Yurov, M., Zhang, J., and Zurek, M.
Published: 2023
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23. Lanadelumab demonstrates rapid and sustained prevention of hereditary angioedema attacks

Author: Riedl, Marc A, Maurer, Marcus, Bernstein, Jonathan A, Banerji, Aleena, Longhurst, Hilary J, Li, H Henry, Lu, Peng, Hao, James, Juethner, Salomé, Lumry, William R, Hébert, J, Ritchie, B, Sussman, G, Yang, WH, Ettingshausen, C Escuriola, Magerl, M, Martinez‐Saguer, I, Maurer, M, Staubach, P, Zimmer, S, Cicardi, M, Perego, F, Wu, MA, Zanichelli, A, Al‐Ghazawi, A, Shennak, M, Zaragoza‐Urdaz, RH, Ghurye, R, Longhurst, HJ, Zinser, E, Anderson, J, Banerji, A, Baptist, AP, Bernstein, JA, Boggs, PB, Busse, PJ, Christiansen, S, Craig, T, Davis‐Lorton, M, Gierer, S, Gower, RG, Harris, D, Hong, DI, Jacobs, J, Johnston, DT, Levitch, ES, Li, HH, Lockey, RF, Lugar, P, Lumry, WR, Manning, ME, McNeil, DL, Melamed, I, Mostofi, T, Nickel, T, Otto, WR, Petrov, AA, Poarch, K, Radojicic, C, Rehman, SM, Riedl, MA, Schwartz, LB, Shapiro, R, Sher, E, Smith, AM, Smith, TD, Soteres, D, Tachdjian, R, Wedner, HJ, Weinstein, ME, Zafra, H, and Zuraw, BL
Subjects: Neurosciences, Clinical Research, Clinical Trials and Supportive Activities, Evaluation of treatments and therapeutic interventions, 6.1 Pharmaceuticals, Angioedemas, Hereditary, Antibodies, Monoclonal, Humanized, Complement C1 Inhibitor Protein, Humans, Treatment Outcome, durable efficacy, hereditary angioedema, long-term prophylaxis, onset of action, HELP Investigators
Abstract: BackgroundLanadelumab demonstrated efficacy in preventing hereditary angioedema (HAE) attacks in the phase 3 HELP Study.ObjectiveTo assess time to onset of effect and long-term efficacy of lanadelumab, based on exploratory findings from the HELP Study.MethodsEligible patients with HAE type I/II received lanadelumab 150 mg every 4 weeks (q4wks), 300 mg q4wks, 300 mg q2wks, or placebo. Ad hoc analyses evaluated day 0-69 findings using a Poisson regression model accounting for overdispersion. Least-squares mean monthly HAE attack rate for lanadelumab was compared with placebo. Intrapatient comparisons for days 0-69 versus steady state (days 70-182) used a paired t test for continuous endpoints or Kappa statistics for categorical endpoints.ResultsOne hundred twenty-five patients were randomized and treated. During days 0-69, mean monthly attack rate was significantly lower with lanadelumab (0.41-0.76) vs placebo (2.04), including attacks requiring acute treatment (0.33-0.61 vs 1.66) and moderate/severe attacks (0.31-0.48 vs 1.33, all P ≤ .001). More patients receiving lanadelumab vs placebo were attack free (37.9%-48.1% vs 7.3%) and responders (85.7%-100% vs 26.8%). During steady state, the efficacy of lanadelumab vs placebo was similar or improved vs days 0-69. Intrapatient differences were significant with lanadelumab 300 mg q4wks for select outcomes. Lanadelumab efficacy was durable-HAE attack rate was consistently lower vs placebo, from the first 2 weeks of treatment through study end. Treatment emergent adverse events were comparable during days 0-69 and 70-182.ConclusionProtection with lanadelumab started from the first dose and continued throughout the entire study period.
Published: 2020

24. A VLT/FLAMES survey for massive binaries in Westerlund 1: VI. Properties of X-ray bright massive cluster members

Author: Clark, J. S., Ritchie, B. W., and Negueruela, I.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: Despite the first detection of X-rays from massive stars occurring four decades ago, the physical dependence of the emission mechanism(s) on the underlying stellar and binary properties of the emitters remains uncertain. The young massive cluster Westerlund 1 provides an ideal testbed for understanding this phenomenon, with over 50 cluster members detected in historical X-ray observations. In the decade since these data were obtained, significant new multi-epoch observations of the cluster have been made, allowing a fundamental reappraisal of the nature of both X-ray bright and dark stars. A total of 45 X-ray sources within Wd1 now have precise spectral classifications. These observations identify 16 candidate and confirmed massive binaries; by comparison 22 stars have X-ray properties that imply a contribution from a wind collision zone. X-ray emission appears confined to O9-B0.5 supergiants, Wolf-Rayets and a small group of highly luminous interacting/post-interaction binaries. Despite their presence in large numbers, no emission is seen from earlier, less evolved O stars or later, cooler B super-/hypergiants. We suppose that the lack of X-ray emission from O giants is due to their comparatively low bolometric luminosities if, as expected, they follow the canonical L_X/L_bol relation for hot stars. The transition away from X-ray emission for OB supergiants occurs at the location of the bistability jump; we speculate that below this limit, stellar wind velocities are insufficient for internal, X-ray emitting shocks to form. Our results are consistent with recent findings that massive binaries are not uniformly brighter than single stars of comparable luminosity and spectral type, although it is noteworthy that the brightest and hardest stellar X-ray sources within Wd1 are all either confirmed or candidate massive, interacting/post-interaction binaries (Abridged)., Comment: 10 pages, 2 figures, accepted for publication in Astronomy and Astrophysics
Published: 2019
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25. First Measurements of the Double-Polarization Observables $F$, $P$, and $H$ in $\omega$ Photoproduction off Transversely Polarized Protons in the $N^\ast$ Resonance Region

Author: Roy, P., Park, S., Crede, V., Anisovich, A. V., Klempt, E., Nikonov, V. A., Sarantsev, A. V., Wei, N. C., Huang, F., Nakayama, K., Adhikari, K. P., Adhikari, S., Angelini, G., Avakian, H., Barion, L., Battaglieri, M., Bedlinskiy, I., Biselli, A. S., Boiarinov, S., Briscoe, W. J., Brock, J., Brooks, W. K., Burkert, V. D., Cao, F., Carlin, C., Carman, D. S., Celentano, A., Chatagnon, P., Chetry, T., Ciullo, G., Cole, P. L., Contalbrigo, M., Cortes, O., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Diehl, S., Djalali, C., Dugger, M., Dupre, R., Duran, B., Egiyan, H., Ehrhart, M., Alaoui, A. El, Fassi, L. El, Eugenio, P., Fegan, S., Filippi, A., Fradi, A., Gilfoyle, G. P., Girod, F. X., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Guo, L., Hafidi, K., Hanretty, C., Harrison, N., Hattawy, M., Hayward, T. B., Heddle, D., Hicks, K., Holtrop, M., Ilieva, Y., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Jo, H. S., Johnston, S., Joosten, S., Kabir, M. L., Keith, C. D., Keller, D., Khachatryan, G., Khachatryan, M., Khanal, A., Khandaker, M., Kim, A., Kim, W., Klein, F. J., Kubarovsky, V., Kuleshov, S. V., Kunkel, M. C., Lanza, L., Lenisa, P., Livingston, K., MacGregor, I. J. D., Marchand, D., McKinnon, B., Meekins, D. G., Meyer, C. A., Mineeva, T., Mokeev, V., Montgomery, R. A., Movsisyan, A, Camacho, C. Munoz, Nadel-Turonski, P., Niccolai, S., Niculescu, G., Osipenko, M., Ostrovidov, A. I., Paolone, M., Pappalardo, L. L., Paremuzyan, R., Pasyuk, E., Payette, D., Phelps, W., Pierce, J., Pogorelko, O., Prok, Y., Protopopescu, D., Raue, B. A., Ripani, M., Riser, D., Ritchie, B. G., Rizzo, A., Rosner, G., Sabatie, F., Salgado, C., Schumacher, R. A., Seely, M. L., Sharabian, Y. G., Shrestha, U., Skorodumina, Iu., Sokhan, D., Soto, O., Sparveris, N., Strakovsky, I. I., Strauch, S., Taiuti, M., Tan, J. A., Torayev, B., Tyler, N., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N. K., Wang, R., Watts, D. P., Wei, X., Wood, M. H., Zachariou, N., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: First measurements of double-polarization observables in $\omega$ photoproduction off the proton are presented using transverse target polarization and data from the CEBAF Large Acceptance Spectrometer (CLAS) FROST experiment at Jefferson Lab. The beam-target asymmetry $F$ has been measured using circularly polarized, tagged photons in the energy range 1200 - 2700 MeV, and the beam-target asymmetries $H$ and $P$ have been measured using linearly polarized tagged photons in the energy range 1200 - 2000 MeV. These measurements significantly increase the database on polarization observables. The results are included in two partial-wave analyses and reveal significant contributions from several nucleon ($N^\ast$) resonances. In particular, contributions from new $N^\ast$ resonances listed in the Review of Particle Properties are observed, which aid in reaching the goal of mapping out the nucleon resonance spectrum., Comment: Two authors added, figures updated
Published: 2018
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26. A VLT/FLAMES survey for massive binaries in Westerlund 1 V. the X-ray selected blue stragglers Wd1-27 and -30a

Author: Clark, J. S., Najarro, F., Negueruela, I., Ritchie, B. W., Gonzalez-Fernandez, C., and Lohr, M. E.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: Observational studies suggest that many OB stars are found within binary systems which may be expected to interact during their lifetimes. Significant mass transfer or merger of both components will modify evolutionary pathways, facilitating the production of exceptionally massive stars which will present as blue stragglers. Identification and characterisation of such objects is crucial if the outcomes of binary evolutionary channels are to be quantified. The massive cluster Westerlund 1 hosts a rich population of X-ray bright stars where the emission is thought to derive from the wind collision zones of massive binaries. Selected on this basis, we present the results of a multiwavelength analysis of the X-ray luminous O stars Wd1-27 and -30a. We find both to be early/mid-O hypergiants with luminosities, temperatures and masses significantly in excess of other early stars within Wd1, hence qualifying as massive blue stragglers. The nature of Wd1-27 remains uncertain but the detection of radial velocity changes and the X-ray properties of Wd1-30a suggest that it is a binary. Analysis of Gaia proper motion and parallactic data indicates that both are cluster members; we also provide a membership list for Wd1 based on this analysis. The presence of hypergiants of spectral types O to M within Wd1 cannot be understood via single-star evolution. We suppose that the early-B and mid-O hypergiants formed via binary-induced mass-stripping of the primary and mass-transfer to the secondary, respectively. This implies that for a subset of objects massive star-formation may be regarded as a two-stage process, with binary-driven mass-transfer or merger yielding stars with masses significantly in excess of their initial birth mass (Abridged)., Comment: 19 pages, 9 figures, accepted for publication in Astronomy and Astrophysics
Published: 2018
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27. An ALMA 3mm continuum census of Westerlund 1

Author: Fenech, D. M., Clark, J. S., Prinja, R. K., Dougherty, S., Najarro, F., Negueruela, I., Richards, A., Ritchie, B. W., and Andrews, H.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: Massive stars play an important role in both cluster and galactic evolution and the rate at which they lose mass is a key driver of both their own evolution and their interaction with the environment up to and including their SNe explosions. Young massive clusters provide an ideal opportunity to study a co-eval population of massive stars. We performed 3mm continuum observations with the Atacama Large Millimetre/submillimetre Array of the Galactic cluster Westerlund 1, to study the constituent massive stars and determine mass-loss rates for the diverse post-main sequence population. We detected emission from 50 stars in Westerlund 1, comprising all 21 Wolf-Rayets within the field of view, eight cool and 21 OB super-/hypergiants. Emission nebulae were associated with a number of the cool hypergiants while, unexpectedly, a number of hot stars also appear spatially resolved. We measured the mass-loss rates for a unique population of massive post-main sequence stars at every stage of evolution, confirming a significant increase as stars transition from OB supergiant to WR states. The range of spectral types exhibited provides a critical test of radiatively driven wind theory and the reality of the bi-stability jump. The extreme mass-loss rate inferred for the interacting binary Wd1-9 in comparison to other cluster members confirmed the key role binarity plays in massive stellar evolution. The presence of compact nebulae around a number of OB and WR stars is unexpected; by analogy to the cool super-/hypergiants we attribute this to confinement and sculpting of the stellar wind via interaction with the intra-cluster medium/wind. Given the morphology of core collapse SNe depend on the nature of the pre-explosion circumstellar environment, if this hypothesis is correct then the properties of the explosion depend not just on the progenitor, but also the environment in which it is located., Comment: 35 pages, 20 figures, accepted for publication in A&A
Published: 2018
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28. Proton-$\eta^\prime$ interactions at threshold

Author: Anisovich, A. V., Burkert, V., Dugger, M., Klempt, E., Nikonov, V. A., Ritchie, B. G., Sarantsev, A. V., and Thoma, U.
Subjects: Nuclear Experiment
Abstract: Recent data on photoproduction of $\eta'$ mesons off protons have been included in the data base for the Bonn-Gatchina partial wave analysis. The real and imaginary parts of the $S$-wave $\eta^\prime p\to \eta^\prime p$ scattering amplitude in the threshold region were fit to yield the $\eta^\prime p$ scattering length and the interaction range. This new analysis found $|a_{\eta^\prime p}|= (0.403\pm 0.015\pm 0.060)$ fm and a phase $\phi=(87\pm2)^\circ$, while the range parameter is not well-constrained. The striking behavior of the GRAAL data on the beam asymmetry in the threshold region suggests that a narrow proton-$\eta'$ resonance might exist. However, the scattering length was found to be relatively insensitive to the possible existence of this narrow resonance., Comment: 5 pages, 5 figures
Published: 2018
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29. Double $K_S^0$ Photoproduction off the Proton at CLAS

Author: Chandavar, S., Goetz, J. T., Hicks, K., Keller, D., Kunkel, M. C., Paolone, M., Weygand, D. P., Adhikari, K. P., Adhikari, S., Akbar, Z., Ball, J., Balossino, I., Barion, L., Bashkanov, M., Battaglieri, M., Bedlinskiy, I., Biselli, A. S., Briscoe, W. J., Brooks, W. K., Burkert, V. D., Cao, F., Carman, D. S., Celentano, A., Charles, G., Chetry, T., Ciullo, G., Clark, L., Cole, P. L., Contalbrigo, M., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Defurne, M., Deur, A., Djalali, C., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Eugenio, P., Fedotov, G., Filippi, A., Fradi, A., Gavalian, G., Ghandilyan, Y., Gilfoyle, G. P., Girod, F. X., Glazier, D. I., Gohn, W., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Hattawy, M., Heddle, D., Holtrop, M., Ilieva, Y., Ireland, D. G., Isupov, E. L., Jenkins, D., Johnston, S., Joo, K., Joosten, S., Kabir, M. L., Khachatryan, G., Khachatryan, M., Khandaker, M., Kim, W., Klein, A., Klein, F. J., Kubarovsky, V., Lanza, L., Lenisa, P., Livingston, K., MacGregor, I. J. D., Markov, N., McCracken, M. E., McKinnon, B., Meyer, C. A., Mineeva, T., Mokeev, V., Movsisyan, A, Camacho, C. Munoz, Nadel-Turonski, P., Niccolai, S., Niculescu, G., Osipenko, M., Ostrovidov, A. I., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, W., Pogorelko, O., Price, J. W., Prok, Y., Protopopescu, D., Raue, B. A., Ripani, M., Riser, D., Ritchie, B. G., Rizzo, A., Rosner, G., Sabatie, F., Salgado, C., Schumacher, R. A., Sharabian, Y. G., Simonyan, A., Skorodumina, Iu., Sokhan, D., Smith, G. D., Sparveris, N., Stepanyan, S., Strakovsky, I. I., Strauch, S., Ungaro, M., Voutier, E., Wei, X., Zachariou, N., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment
Abstract: The $f_0$(1500) meson resonance is one of several contenders to have significant mixing with the lightest glueball. This resonance is well established from several previous experiments. Here we present the first photoproduction data for the $f_0$(1500) via decay into the $K_S^0 K_S^0$ channel using the CLAS detector. The reaction $\gamma p$ -> $f_0 p$ -> $K_S^0 K_S^0 p$, where J = 0, 2, was measured with photon energies from 2.7 to 5.1 GeV. A clear peak is seen at 1500 MeV in the background subtracted invariant mass spectra of the two kaons. This is enhanced if the measured 4-momentum transfer to the proton target is restricted to be less than 1.0 GeV2. By comparing data with simulations, it can be concluded that the peak at 1500 MeV is produced primarily at low t, which is consistent with a t-channel production mechanism., Comment: 12 pages, 12 figures
Published: 2017
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30. Measurement of the beam asymmetry $\Sigma$ and the target asymmetry $T$ in the photoproduction of $\omega$ mesons off the proton using CLAS at Jefferson Laboratory

Author: Roy, P., Akbar, Z., Park, S., Crede, V., Anisovich, A. V., Denisenko, I., Klempt, E., Nikonov, V. A., Sarantsev, A. V., Adhikari, K. P., Adhikari, S., Pereira, S. Anefalos, Ball, J., Balossino, I., Bashkanov, M., Battaglieri, M., Batourine, V., Bedlinskiy, I., Biselli, A. S., Boiarinov, S., Briscoe, W. J., Brock, J., Brooks, W. K., Burkert, V. D., Carlin, C., Carman, D. S., Celentano, A., Charles, G., Chetry, T., Ciullo, G., Clary, B. A., Cole, P. L., Contalbrigo, M., D'Angelo, A., Dashyan, N., De Vita, R., Deur, A., Djalali, C., Dugger, M., Dupre, R., Alaoui, A. El, Fassi, L. El, Elouadrhiri, L., Eugenio, P., Fedotov, G., Fegan, S., Filippi, A., Fradi, A., Gavalian, G., Gevorgyan, N., Gilfoyle, G. P., Giovanetti, K. L., Girod, F. X., Gleason, C., Gohn, W., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Hattawy, M., Hicks, K., Holtrop, M., Ilieva, Y., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Joo, K., Joosten, S., Keith, C. D., Keller, D., Khachatryan, G., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F. J., Kubarovsky, V., Kuleshov, S. V., Lanza, L., Lenisa, P., Livingston, K., Lu, H. Y., MacGregor, I. J. D., Markov, N., Mayer, M., McCracken, M. E., McKinnon, B., Meekins, D. G., Meyer, C. A., Meziani, Z. E., Mineeva, T., Mokeev, V., Montgomery, R. A., Movsisyan, A., Camacho, C. Munoz, Nadel-Turonski, P., Niccolai, S., Niculescu, G., Osipenko, M., Ostrovidov, A. I., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, E., Phelps, W., Pierce, J. J., Pogorelko, O., Price, J. W., Procureur, S., Prok, Y., Protopopescu, D., Raue, B. A., Ripani, M., Riser, D., Ritchie, B. G., Rizzo, A., Rosner, G., Sabatie, F., Salgado, C., Schumacher, R. A., Sharabian, Y. G., Skorodumina, Iu., Smith, G. D., Sober, D. I., Sokhan, D., Sparveris, N., Stepanyan, S., Strakovsky, I. I., Strauch, S., Taiuti, M., Tan, J. A., Torayev, B., Ungaro, M., Voutier, E., Walford, N. K., Watts, D. P., Wei, X., Wood, M. H., Zachariou, N., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: The photoproduction of $\omega$ mesons off the proton has been studied in the reaction $\gamma p\to p\,\omega$ using the CEBAF Large Acceptance Spectrometer (CLAS) and the frozen-spin target (FROST) in Hall B at the Thomas Jefferson National Accelerator Facility. For the first time, the target asymmetry, $T$, has been measured in photoproduction from the decay $\omega\to\pi^+\pi^-\pi^0$, using a transversely-polarized target with energies ranging from just above the reaction threshold up to 2.8 GeV. Significant non-zero values are observed for these asymmetries, reaching about 30-40% in the third-resonance region. New measurements for the photon-beam asymmetry, $\Sigma$, are also presented, which agree well with previous CLAS results and extend the world database up to 2.1 GeV. These data and additional $\omega$-photoproduction observables from CLAS were included in a partial-wave analysis within the Bonn-Gatchina framework. Significant contributions from $s$-channel resonance production were found in addition to $t$-channel exchange processes., Comment: 15 pages, 10 figures, author list and references updated
Published: 2017
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31. Measurement of the helicity asymmetry $E$ in $\omega\to\pi^+\pi^-\pi^0$ photoproduction

Author: Akbar, Z., Roy, P., Park, S., Crede, V., Anisovich, A. V., Denisenko, I., Klempt, E., Nikonov, V. A., Sarantsev, A. V., Adhikari, K. P., Adhikari, S., Amaryan, M. J., Pereira, S. Anefalos, Avakian, H., Ball, J., Battaglieri, M., Batourine, V., Bedlinskiy, I., Boiarinov, S., Briscoe, W. J., Brock, J., Brooks, W. K., Burkert, V. D., Cao, F. T., Carlin, C., Carman, D. S., Celentano, A., Charles, G., Chetry, T., Ciullo, G., Clark, L., Cole, P. L., Contalbrigo, M., Cortes, O., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Dugger, M., Dupre, R., Egiyan, H., Fassi, L. El, Eugenio, P., Fedotov, G., Fersch, R., Filippi, A., Fradi, A., Garcon, M., Gevorgyan, N., Giovanetti, K. L., Girod, F. X., Gleason, C., Gohn, W., Golovach, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Hattawy, M., Heddle, D., Hicks, K., Hollis, G., Holtrop, M., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Joosten, S., Keith, C. D., Keller, D., Khachatryan, G., Khachatryan, M., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F. J., Kubarovsky, V., Lanza, L., Livingston, K., MacGregor, I. J. D., Markov, N., McKinnon, B., Meekins, D. G., Mineeva, T., Mokeev, V., Movsisyan, A., Camacho, C. Munoz, Nadel-Turonski, P., Niccolai, S., Osipenko, M., Ostrovidov, A. I., Paolone, M., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, W., Pogorelko, O., Price, J. W., Prok, Y., Protopopescu, D., Raue, B. A., Ripani, M., Ritchie, B. G., Rizzo, A., Rosner, G., Sabatie, F., Salgado, C., Schumacher, R. A., Sharabian, Y. G., Skorodumina, Iu., Smith, G. D., Sober, D. I., Sokhan, D., Sparveris, N., Stepanyan, S., Strakovsky, I. I., Strauch, S., Taiuti, M., Ungaro, M., Voskanyan, H., Voutier, E., Wei, X., Wood, M. H., Zachariou, N., Zana, L., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: The double-polarization observable $E$ was studied for the reaction $\gamma p\to p\omega$ using the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at the Thomas Jefferson National Accelerator Facility and the longitudinally-polarized frozen-spin target (FROST). The observable was measured from the charged decay mode of the meson, $\omega\to\pi^+\pi^-\pi^0$, using a circularly-polarized tagged-photon beam with energies ranging from the $\omega$ threshold at 1.1 to 2.3 GeV. A partial-wave analysis within the Bonn-Gatchina framework found dominant contributions from the $3/2^+$ partial wave near threshold, which is identified with the sub-threshold $N(1720)\,3/2^+$ nucleon resonance. To describe the entire data set, which consisted of $\omega$ differential cross sections and a large variety of polarization observables, further contributions from other nucleon resonances were found to be necessary. With respect to non-resonant mechanisms, $\pi$ exchange in the $t$-channel was found to remain small across the analyzed energy range, while pomeron $t$-channel exchange gradually grew from the reaction threshold to dominate all other contributions above $W \approx 2$ GeV., Comment: 12 pages, 8 figures
Published: 2017
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32. First Exclusive Measurement of Deeply Virtual Compton Scattering off $^4$He: Toward the 3D Tomography of Nuclei

Author: Hattawy, M., Baltzell, N. A., Dupré, R., Hafidi, K., Stepanyan, S., Bültmann, S., De Vita, R., Alaoui, A. El, Fassi, L. El, Egiyan, H., Girod, F. X., Guidal, M., Jenkins, D., Liuti, S., Perrin, Y., Torayev, B., Voutier, E., Adhikari, K. P., Adhikari, S., Adikaram, D., Akbar, Z., Amaryan, M. J., Pereira, S. Anefalos, Armstrong, Whitney R., Avakian, H., Ball, J., Bashkanov, M., Battaglieri, M., Batourine, V., Bedlinskiy, I., Biselli, A. S., Boiarinov, S., Briscoe, W. J., Brooks, W. K., Burkert, V. D., Cao, Frank Thanh, Carman, D. S., Celentano, A., Charles, G., Chetry, T., Ciullo, G., Clark, L., Colaneri, L., Cole, P. L., Contalbrigo, M., Cortes, O., Crede, V., D'Angelo, A., Dashyan, N., De Sanctis, E., Deur, A., Djalali, C., Elouadrhiri, L., Eugenio, P., Fedotov, G., Fegan, S., Fersch, R., Filippi, A., Fleming, J. A., Forest, T. A., Fradi, A., Garçon, M., Gevorgyan, N., Ghandilyan, Y., Gilfoyle, G. P., Giovanetti, K. L., Gleason, C., Gohn, W., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guo, L., Hakobyan, H., Hanretty, C., Harrison, N., Heddle, D., Hicks, K., Holtrop, M., Hughes, S. M., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jiang, H., Joo, K., Joosten, S., Keller, D., Khachatryan, G., Khachatryan, M., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F. J., Kubarovsky, V., Kuhn, S. E., Kuleshov, S. V., Lanza, L., Lenisa, P., Livingston, K., Lu, H. Y., MacGregor, I . J . D., Markov, N., Mayer, M., McCracken, M. E., McKinnon, B., Meyer, C. A., Meziani, Z. E., Mineeva, T., Mirazita, M., Mokeev, V., Montgomery, R. A., Moutarde, H., Movsisyan, A, Camacho, C. Munoz, Nadel-Turonski, P., Net, L. A., Niccolai, S., Niculescu, G., Niculescu, I., Osipenko, M., Ostrovidov, A. I., Paolone, M., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, E., Phelps, W., Pisano, S., Pogorelko, O., Price, J. W., Prok, Y., Protopopescu, D., Ripani, M., Ritchie, B. G., Rizzo, A., Rosner, G., Rossi, P., Sabatié, F., Salgado, C., Schumacher, R. A., Seder, E., Sharabian, Y. G., Simonyan, A., Skorodumina, Iu., Smith, G. D., Sokhan, D., Sparveris, N., Strauch, S., Taiuti, M., Ungaro, M., Voskanyan, H., Walford, N. K., Watts, D. P., Wei, X., Weinstein, L. B., Wood, M. H., Zachariou, N., Zana, L., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: We report on the first measurement of the beam-spin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment used the 6 GeV electron beam from the CEBAF accelerator at Jefferson Lab incident on a pressurized $^4$He gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron was detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber was used to detect the recoiling $^4$He nuclei. We measured beam-spin asymmetries larger than those observed on the free proton in the same kinematic domain. From these, we were able to extract, in a model-independent way, the real and imaginary parts of the only $^4$He Compton form factor, $\cal H_A$. This first measurement of coherent deeply virtual Compton scattering on the $^4$He nucleus, with a fully exclusive final state via nuclear recoil tagging, leads the way toward 3D imaging of the partonic structure of nuclei.
Published: 2017
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33. $N^*\to N \eta^\prime$ decays from photoproduction of $\eta^\prime$-mesons off protons

Author: Anisovich, A. V., Burkert, V., Collins, P. M., Dugger, M., Klempt, E., Nikonov, V. A., Ritchie, B. G., Sarantsev, A., and Thoma, U.
Subjects: Nuclear Experiment
Abstract: A study of the partial-wave content of the $\gamma p\to \eta^\prime p$ reaction in the fourth resonance region is presented, which has been prompted by new measurements of polarization observables for that process. Using the Bonn-Gatchina partial-wave formalism, the incorporation of new data indicates that the $N(1895)1/2^-$, $N(1900)3/2^+$, $N(2100)1/2^+$, and $N(2120)3/2^-$ are the most significant contributors to the photoproduction process. New results for the branching ratios of the decays of these more prominent resonances to $N\eta^\prime$ final states are provided; such branches have not been indicated in the most recent edition of the Review of Particle Properties. Based on the analysis performed here, predictions for the helicity asymmetry $E$ for the $\gamma p\to \eta^\prime p$ reaction are presented., Comment: 7 pages, 5 figures, 3 tables
Published: 2017
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34. Photon beam asymmetry $\Sigma$ in the reaction $\vec{\gamma} p \to p \omega$ for $E_\gamma$ = 1.152 to 1.876 GeV

Author: CLAS Collaboration, Collins, P., Ritchie, B. G., Dugger, M., Klein, F. J., Anisovich, A. V., Klempt, E., Nikonov, V. A., Sarantsev, A., Adhikari, K. P., Adhikari, S., Adikaram, D., Akbar, Z., Pereira, S. Anefalos, Avakian, H., Ball, J., Baltzell, N. A., Bashkanov, M., Battaglieri, M., Batourine, V., Bedlinskiy, I., Biselli, A. S., Boiarinov, S., Briscoe, W. J., Brooks, W. K., Burkert, V. D., Cao, Frank Thanh, Cao, T., Carman, D. S., Celentano, A., Charles, G., Chetry, T., Ciullo, G., Clark, L., Cole, P. L., Contalbrigo, M., Cortes, O., Crede, V., Dashyan, N., De Vita, R., De Sanctis, E., Defurne, M., Deur, A., Djalali, C., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Eugenio, P., Fedotov, G., Filippi, A., Fleming, J. A., Ghandilyan, Y., Gilfoyle, G. P., Giovanetti, K. L., Girod, F. X., Glazier, D. I., Gleason, C., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Hattawy, M., Heddle, D., Hicks, K., Hollis, G., Holtrop, M., Hughes, S. M., Ilieva, Y., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Jiang, H., Jo, H. S., Joosten, S., Keller, D., Khachatryan, G., Khachatryan, M., Khandaker, M., Kim, A., Kim, W., Klein, A., Kubarovsky, V., Kuleshov, S. V., Lanza, L., Lenisa, P., Livingston, K., MacGregor, I. J. D., Markov, N., McKinnon, B., Meyer, C. A., Meziani, Z. E., Mineeva, T., Mokeev, V., Montgomery, R. A., Movsisyan, A., Munevar, E., Camacho, C. Munoz, Nadel-Turonski, P., Net, L. A., Niccolai, S., Niculescu, G., Niculescu, I., Osipenko, M., Ostrovidov, A. I., Paolone, M., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, W., Pisano, S., Pogorelko, O., Price, J. W., Procureur, S., Prok, Y., Protopopescu, D., Raue, B. A., Ripani, M., Rizzo, A., Rosner, G., Sabatie, F., Salgado, C., Schumacher, R. A., Sharabian, Y. G., Simonyan, A., Skorodumina, Iu., Smith, G. D., Sober, D. I., Sokhan, D., Sparveris, N., Stankovic, I., Stepanyan, S., Strakovsky, I. I., Strauch, S., Taiuti, M., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N. K., Watts, D. P., Wei, X., Wood, M. H., Zachariou, N., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment
Abstract: Photon beam asymmetry $\Sigma$ measurements for $\omega$ photoproduction in the reaction $\vec{\gamma} p \to \omega p$ are reported for photon energies from 1.152 to 1.876 GeV. Data were taken using a linearly-polarized tagged photon beam, a cryogenic hydrogen target, and the CLAS spectrometer in Hall B at Jefferson Lab. The measurements obtained markedly increase the size of the database for this observable, extend coverage to higher energies, and resolve discrepancies in previously published data. Comparisons of these new results with predictions from a chiral-quark-based model and from a dynamical coupled-channels model indicate the importance of interferences between $t$-channel meson exchange and $s$- and $u$-channel contributions, underscoring sensitivity to the nucleon resonances included in those descriptions. Comparisons with the Bonn-Gatchina partial-wave analysis indicate the $\Sigma$ data reported here help to fix the magnitudes of the interference terms between the leading amplitudes in that calculation (Pomeron exchange and the resonant portion of the $J^P=3/2^+$ partial wave), as well as the resonant portions of the smaller partial waves with $J^P$= $1/2^-$, $3/2^-$, and $5/2^+$., Comment: 10 pages, 3 figures
Published: 2017
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35. Differential Cross Section Measurements for $\gamma n\to\pi^-p$ Above the First Nucleon Resonance Region

Author: Mattione, P. T., Carman, D. S., Strakovsky, I. I., Workman, R. L., Kudryavtsev, A. E., Svarc, A., Tarasov, V. E., Adhikari, K. P., Adhikari, S., Adikaram, D., Akbar, Z., Pereira, S. Anefalos, Ball, J., Baltzell, N. A., Bashkanov, M., Battaglieri, M., Batourine, V., Bedlinskiy, I., Biselli, A. S., Boiarinov, S., Briscoe, W. J., Burkert, V. D., Cao, T., Celentano, A., Charles, G., Chetry, T., Ciullo, G., Clark, L., Cole, P. L., Contalbrigo, M., Cortes, O., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Defurne, M., Deur, A., Djalali, C., Dugger, M., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Eugenio, P., Fedotov, G., Fersch, R., Filippi, A., Fleming, J. A., Fradi, A., Ghandilyan, Y., Gilfoyle, G. P., Giovanetti, K. L., Girod, F. X., Gleason, C., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Hattawy, M., Heddle, D., Hicks, K., Hollis, G., Holtrop, M., Hughes, S. M., Ilieva, Y., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Jiang, H., Jo, H. S., Joo, K., Joosten, S., Keller, D., Khachatryan, G., Khachatryan, M., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F. J., Kubarovsky, V., Kuleshov, S. V., Lanza, L., Lenisa, P., Livingston, K., MacGregor, I. J. D., Markov, N., McKinnon, B., Meyer, C. A., Meziani, Z. E., Mineeva, T., Mokeev, V., Montgomery, R. A., Movsisyan, A, Camacho, C. Munoz, Murdoch, G., Nadel-Turonski, P., Net, L. A., Niccolai, S., Niculescu, G., Niculescu, I., Osipenko, M., Ostrovidov, A. I., Paolone, M., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, W., Pisano, S., Pogorelko, O., Price, J. W., Procureur, S., Prok, Y., Protopopescu, D., Raue, B. A., Ripani, M., Ritchie, B. G., Rizzo, A., Rosner, G., Sabatié, F., Salgado, C., Schumacher, R. A., Sharabian, Y. G., Simonyan, A., Skorodumina, Iu., Smith, G. D., Sokhan, D., Sparveris, N., Stankovic, I., Stepanyan, S., Strauch, S., Taiuti, M., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N. K., Watts, D, Wei, X., Wood, M. H., Zachariou, N., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment
Abstract: The quasi-free $\gamma d\to\pi^{-}p(p)$ differential cross section has been measured with CLAS at photon beam energies $E_\gamma$ from 0.445 GeV to 2.510 GeV (corresponding to $W$ from 1.311 GeV to 2.366 GeV) for pion center-of-mass angles $\cos\theta_\pi^{c.m.}$ from -0.72 to 0.92. A correction for final state interactions has been applied to this data to extract the $\gamma n\to\pi^-p$ differential cross sections. These cross sections are quoted in 8428 $(E_\gamma,\cos\theta_\pi^{c.m.})$ bins, a factor of nearly three increase in the world statistics for this channel in this kinematic range. These new data help to constrain coupled-channel analysis fits used to disentangle the spectrum of $N^*$ resonances and extract their properties. Selected photon decay amplitudes $N^* \to \gamma n$ at the resonance poles are determined for the first time and are reported here.
Published: 2017
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36. The Beam-Target Helicity Asymmetry for $\vec{\gamma} \vec{n} \rightarrow \pi^- p$ in the {\bf{$N^*$} Resonance Region

Author: Ho, D., Peng, P., Bass, C., Collins, P., D'Angelo, A., Deur, A., Fleming, J., Hanretty, C., Kageya, T., Khandaker, M., Klein, F. J., Klempt, E., Laine, V., Lowry, M. M., Lu, H., Nepali, C., Nikonov, V. A., O'Connell, T., Sandorfi, A. M., Sarantsev, A. V., Schumacher, R. A., Strakovsky, I. I., Švarc, A., Walford, N. K., Wei, X., Whisnant, C. S., Workman, R. L., Zonta, I., Adhikari, K. P., Adikaram, D., Akbar, Z., Amaryan, M. J., Pereira, S. Anefalos, Avakian, H., Ball, J., Bashkanov, M., Battaglieri, M., Batourine, V., Bedlinskiy, I., Briscoe, W. J., Burkert, V. D., Carman, D. S., Celentano, A., Charles, G., Chetry, T., Ciullo, G., Clark, L., Colaneri, L., Cole, P. L., Contalbrigo, M., Crede, V., Dashyan, N., De Sanctis, E., De Vita, R., Djalali, C., Dupre, R., Alaoui, A. El, Fassi, L. El, Elouadrhiri, L., Fedotov, G., Fegan, S., Fersch, R., Filippi, A., Fradi, A., Ghandilyan, Y., Gilfoyle, G. P., Girod, F. X., Glazier, D. I., Gleason, C., Gohn, W., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Guo, L., Hakobyan, H., Harrison, N., Hicks, K., Holtrop, M., Hughes, S. M., Ilieva, Y., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Jiang, H., Jo, H. S., Joo, K., Joosten, S., Keller, D., Khachatryan, G., Kim, A., Kim, W., Klein, A., Kubarovsky, V., Kuleshov, S. V., Lanza, L., Lenisa, P., Livingston, K., MacGregor, I . J . D., Markov, N., McKinnon, B., Mineeva, T., Mokeev, V., Montgomery, R. A., Movsisyan, A, Camacho, C. Munoz, Murdoch, G., Niccolai, S., Niculescu, G., Osipenko, M., Paolone, M., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, W., Pogorelko, O., Price, J. W., Procureur, S., Protopopescu, D., Ripani, M., Riser, D., Ritchie, B. G., Rizzo, A., Rosner, G., Sabatié, F., Salgado, C., Sharabian, Y. G., Skorodumina, Iu., Smith, G. D., Sober, D. I., Sokhan, D., Sparveris, N., Strauch, S., Tian, Ye, Torayev, B., Ungaro, M., Voskanyan, H., Watts, D. P., Wood, M. H., Zachariou, N., Zhang, J., and Zhao, Z. W.
Subjects: Nuclear Experiment
Abstract: We report the first beam-target double-polarization asymmetries in the $\gamma + n(p) \rightarrow \pi^- + p(p)$ reaction spanning the nucleon resonance region from invariant mass $W$= $1500$ to $2300$ MeV. Circularly polarized photons and longitudinally polarized deuterons in $H\!D$ have been used with the CLAS detector at Jefferson Lab. The exclusive final state has been extracted using three very different analyses that show excellent agreement, and these have been used to deduce the {\it{E}} polarization observable for an effective neutron target. These results have been incorporated into new partial wave analyses, and have led to significant revisions for several $\gamma nN^*$ resonance photo-couplings., Comment: 6 pages, 5 figures; Physical Review Letters - in press
Published: 2017

37. Design and construction of a high-energy photon polarimeter

Author: Dugger, M., Ritchie, B. G., Sparks, N., Moriya, K., Tucker, R. J., Lee, R. J., Thorpe, B. N., Hodges, T., Barbosa, F. J., Sandoval, N., and Jones, R. T.
Subjects: Physics - Instrumentation and Detectors, Nuclear Experiment
Abstract: We report on the design and construction of a high-energy photon polarimeter for measuring the degree of polarization of a linearly-polarized photon beam. The photon polarimeter uses the process of pair production on an atomic electron (triplet production). The azimuthal distribution of scattered atomic electrons following triplet production yields information regarding the degree of linear polarization of the incident photon beam. The polarimeter, operated in conjunction with a pair spectrometer, uses a silicon strip detector to measure the recoil electron distribution resulting from triplet photoproduction in a beryllium target foil. The analyzing power $\Sigma_A$ for the device using a 75 $\rm{\mu m}$ beryllium converter foil is about 0.2, with a relative systematic uncertainty in $\Sigma_A$ of 1.5%., Comment: 13 pages, 17 figures
Published: 2017
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38. Photon beam asymmetry $\Sigma$ for $\eta$ and $\eta^\prime$ photoproduction from the proton

Author: Collins, P., Ritchie, B. G., Dugger, M., Anisovich, A. V., Döring, M., Klempt, E., Nikonov, V. A., Rönchen, D., Sadasivan, D., Sarantsev, A., Adhikaria, K. P., Akbar, Z., Amaryana, M. J., Pereira, S. Anefalos, Avakiana, H., Ball, J., Balossino, I., Bashkanova, M., Battaglieri, M., Bedlinskiy, I., Bisellik, A. S., Briscoe, W. J., Brooks, W. K., Burkert, V. D., Cao, Frank Thanh, Carman, D. S., Celentano, A., Chandavar, S., Charles, G., Chetry, T., Ciullo, G., Clark, L., Colaneri, L., Cole, P. L., Compton, N., Contalbrigo, M., Cortes, O., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Elouadrhiri, L., Eugenio, P., Fanchini, E., Fedotov, G., Filippi, A., Fleming, J. A., Ghandilyan, Y., Gilfoyle, G. P., Giovanetti, K. L., Girod, F. X., Glazier, D. I., Gleason, C., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Heddle, D., Hicks, K., Holtrop, M., Hughes, S. M., Ilieva, Y., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Jo, H. S., Joosten, S., Keller, D., Khachatryan, G., Khachatryan, M., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F. J., Kubarovsky, V., Lanza, L., Lenisa, P., Livingston, K., MacGregor, I. J. D., Markov, N., McKinnon, B., Meyer, C. A., Mirazita, M., Mokeev, V., Montgomery, R. A., Movsisyan, A, Camacho, C. Munoz, Murdoch, G., Nadel-Turonski, P., Niccolai, S., Niculescu, G., Niculescu, I., Osipenko, M., Ostrovidov, A. I., Paolone, M., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, W., Pisano, S., Pogorelko, O., Price, J. W., Prok, Y., Protopopescu, D., Raue, B. A., Ripani, M., Rizzo, A., Rosner, G., Roy, P., Sabatié, F., Salgado, C., Schumacher, R. A., Sharabian, Y. G., Skorodumina, Iu., Smith, G. D., Sokhan, D., Sparveris, N., Stepanyan, S., Strakovsky, I. I., Strauch, S., Taiuti, M., Tian, Ye, Torayev, B., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N. K., Wei, X., Zachariou, N., and Zhang, J.
Subjects: Nuclear Experiment
Abstract: Measurements of the linearly-polarized photon beam asymmetry $\Sigma$ for photoproduction from the proton of $\eta$ and $\eta^\prime$ mesons are reported. A linearly-polarized tagged photon beam produced by coherent bremsstrahlung was incident on a cryogenic hydrogen target within the CEBAF Large Acceptance Spectrometer. Results are presented for the $\gamma p \to \eta p$ reaction for incident photon energies from 1.070 to 1.876 GeV, and from 1.516 to 1.836 GeV for the $\gamma p \to \eta^\prime p$ reaction. For $\gamma p \to \eta p$, the data reported here considerably extend the range of measurements to higher energies, and are consistent with the few previously published measurements for this observable near threshold. For $\gamma p \to \eta^\prime p$, the results obtained are consistent with the few previously published measurements for this observable near threshold, but also greatly expand the incident photon energy coverage for that reaction. Initial analysis of the data reported here with the Bonn-Gatchina model strengthens the evidence for four nucleon resonances -- the $N(1895)1/2^-$, $N(1900)3/2^+$, $N(2100)1/2^+$ and $N(2120)3/2^-$ resonances -- which presently lack the "four-star" status in the current Particle Data Group compilation, providing examples of how these new measurements help refine models of the photoproduction process., Comment: 10 pages, 3 figures
Published: 2017
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39. Measurement of the beam asymmetry $\Sigma$ for $\pi^0$ and $\eta$ photoproduction on the proton at $E_\gamma = 9$ GeV

Author: GlueX Collaboration, Ghoul, H. Al, Anassontzis, E. G., Austregesilo, A., Barbosa, F., Barnes, A., Beattie, T. D., Bennett, D. W., Berdnikov, V. V., Black, T., Boeglin, W., Briscoe, W. J., Brooks, W. K., Cannon, B. E., Chernyshov, O., Chudakov, E., Crede, V., Dalton, M. M., Deur, A., Dobbs, S., Dolgolenko, A., Dugger, M., Dzhygadlo, R., Egiyan, H., Eugenio, P., Fanelli, C., Foda, A. M., Frye, J., Furletov, S., Gan, L., Gasparian, A., Gerasimov, A., Gevorgyan, N., Goetzen, K., Goryachev, V. S., Guo, L., Hakobyan, H., Hardin, J., Henderson, A., Huber, G. M., Ireland, D. G., Ito, M. M., Jarvis, N. S., Jones, R. T., Kakoyan, V., Kamel, M., Klein, F. J., Kliemt, R., Kourkoumeli, C., Kuleshov, S., Kuznetsov, I., Lara, M., Larin, I., Lawrence, D., Levine, W. I., Livingston, K., Lolos, G. J., Lyubovitskij, V., Mack, D., Mattione, P. T., Matveev, V., McCaughan, M., McCracken, M., McGinley, W., McIntyre, J., Mendez, R., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mokaya, F., Moriya, K., Nerling, F., Nigmatkulov, G., Ochoa, N., Ostrovidov, A. I., Papandreou, Z., Patsyuk, M., Pedroni, R., Pennington, M. R., Pentchev, L., Peters, K. J., Pooser, E., Pratt, B., Qiang, Y., Reinhold, J., Ritchie, B. G., Robison, L., Romanov, D., Salgado, C., Schumacher, R. A., Schwarz, C., Schwiening, J., Semenov, A. Yu., Semenova, I. A., Seth, K. K., Shepherd, M. R., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Sparks, N., Staib, M. J., Stevens, J. R., Strakovsky, I. I., Subedi, A., Tarasov, V., Taylor, S., Teymurazyan, A., Tolstukhin, I., Tomaradze, A., Toro, A., Tsaris, A., Vasileiadis, G., Vega, I., Walford, N. K., Werthmuller, D., Whitlatch, T., Williams, M., Wolin, E., Xiao, T., Zarling, J., Zhang, Z., Zihlmann, B., Mathieu, V., and Nys, J.
Subjects: Nuclear Experiment
Abstract: We report measurements of the photon beam asymmetry $\Sigma$ for the reactions $\vec{\gamma}p\to p\pi^0$ and $\vec{\gamma}p\to p\eta $ from the GlueX experiment using a 9 GeV linearly-polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous $\pi^0$ measurements and are the first $\eta$ measurements in this energy regime. The results are compared with theoretical predictions based on $t$-channel, quasi-particle exchange and constrain the axial-vector component of the neutral meson production mechanism in these models., Comment: 6 pages, 6 figures, Published in Physical Review C: Rapid Communication
Published: 2017
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40. First Results from The GlueX Experiment

Author: The GlueX Collaboration, Ghoul, H. Al, Anassontzis, E. G., Barbosa, F., Barnes, A., Beattie, T. D., Bennett, D. W., Berdnikov, V. V., Black, T., Boeglin, W., Brooks, W. K., Cannon, B., Chernyshov, O., Chudakov, E., Crede, V., Dalton, M. M., Deur, A., Dobbs, S., Dolgolenko, A., Dugger, M., Egiyan, H., Eugenio, P., Foda, A. M., Frye, J., Furletov, S., Gan, L., Gasparian, A., Gerasimov, A., Gevorgyan, N., Goryachev, V. S., Guegan, B., Guo, L., Hakobyan, H., Hakobyan2, H., Hardin, J., Huber, G. M., Ireland, D., Ito, M. M., Jarvis, N. S., Jones, R. T., Kakoyan, V., Kamel, M., Klein, F. J., Kourkoumeli, C., Kuleshov, S., Lara, M., Larin, I., Lawrence, D., Leckey, J., Levine, W. I., Livingston, K., Lolos, G. J., Mack, D., Mattione, P. T., Matveev, V., McCaughan, M., McGinley, W., McIntyre, J., Mendez, R., Meyer, C. A., Miskimen, R., Mitchell, R. E., Mokaya, F., Moriya, K., Nigmatkulov, G., Ochoa, N., Ostrovidov, A. I., Papandreou, Z., Pedroni, R., Pennington, M., Pentchev, L., Ponosov, A., Pooser, E., Pratt, B., Qiang, Y., Reinhold, J., Ritchie, B. G., Robison, L., Romanov, D., Salgado, C., Schumacher, R. A., Semenov, A. Yu., Semenova, I. A., Senderovich, I., Seth, K. K., Shepherd, M. R., Smith, E. S., Sober, D. I., Somov, A., Somov, S., Soto, O., Sparks, N., Staib, M. J., Stevens, J. R., Subedi, A., Tarasov, V., Taylor, S., Tolstukhin, I., Tomaradze, A., Toro, A., Tsaris, A., Vasileiadis, G., Vega, I., Voulgaris, G., Walford, N. K., Whitlatch, T., Williams, M., Wolin, E., Xiao, T., Zarling, J., and Zihlmann, B.
Subjects: Nuclear Experiment, High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract: The GlueX experiment at Jefferson Lab ran with its first commissioning beam in late 2014 and the spring of 2015. Data were collected on both plastic and liquid hydrogen targets, and much of the detector has been commissioned. All of the detector systems are now performing at or near design specifications and events are being fully reconstructed, including exclusive production of $\pi^{0}$, $\eta$ and $\omega$ mesons. Linearly-polarized photons were successfully produced through coherent bremsstrahlung and polarization transfer to the $\rho$ has been observed., Comment: 8 pages, 6 figures, Invited contribution to the Hadron 2015 Conference, Newport News VA, September 2015
Published: 2015
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41. First measurement of the helicity asymmetry $E$ in $\eta$ photoproduction on the proton

Author: Senderovich, I., Morrison, B. T., Dugger, M., Ritchie, B. G., Pasyuk, E., Tucker, R., Brock, J., Carlin, C., Keith, C. D., Meekins, D. G., Seely, M. L., R, D., D, M., Collins, P., Adhikari, K. P., Adikaram, D., Akbar, Z., Anderson, M. D., Pereira, S. Anefalos, Badui, R. A., Ball, J., Baltzell, N. A., Battaglieri, M., Batourine, V., Bedlinskiy, I., Biselli, A. S., Boiarinov, S., Briscoe, W. J., Brooks, W. K., Burkert, V. D., Carman, D. S., Celentano, A., Chandavar, S., Charles, G., Colaneri, L., Cole, P. L., Contalbrigo, M., Cortes, O., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Fradi, A., Elouadrhiri, L., Eugenio, P., Fedotov, G., Fegan, S., Filippi, A., Fleming, J. A., Garillon, B., Ghandilyan, Y., Gilfoyle, G. P., Giovanetti, K. L., Girod, F. -X., Glazier, D. I., Goetz, J. T., Gohn, W., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Hattawy, M., Hicks, K., Ho, D., Holtrop, M., Hughes, S. M., Ilieva, Y., Ireland, D. G., Ishkhanov, B. S., Jenkins, D., Jiang, H., Jo, H. S., Joo, K., Joosten, S., Keller, D., Khachatryan, G., Khandaker, M., Kim, A., Klein, F. J., Kubarovsky, V., Kunkel, M. C., Lenisa, P., Livingston, K., Lu, H. Y., MacGregor, I. J. D., Mattione, P., McKinnon, B., Meyer, C. A., Mineeva, T., Mokeev, V., Montgomery, R. A., Movsisyan, A., Camacho, C. Munoz, Nadel-Turonski, P., Net, L. A., Niccolai, S., Niculescu, G., Niculescu, I., Osipenko, M., Park, K., Park, S., Peng, P., Phelps, W., Pisano, S., Pogorelko, O., Price, J. W., Prok, Y., Puckett, A. J. R., Ripani, M., Rizzo, A., Rosner, G., Roy, P., Sabatie, F., Salgado, C., Schott, D., Schumacher, R. A., Seder, E., Simonyan, A., Skorodumina, Iu., Smith, G. D., Sober, D. I., Sokhan, D., Sparveris, N., Stepanyan, S., Stoler, P., Strakovsky, I. I., Strauch, S., Sytnik, V., Tian, Ye, Ungaro, M., Voskanyan, H., Voutier, E., Walford, N. K., Wei, X., Wood, M. H., Zachariou, N., Zana, L., Zhang, J., Zhao, Z. W., and Zonta, I.
Subjects: Nuclear Experiment
Abstract: Results are presented for the first measurement of the double-polarization helicity asymmetry E for the $\eta$ photoproduction reaction $\gamma p \rightarrow \eta p$. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the J\"ulich model to examine the case for the existence of a narrow $N^*$ resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the E observable using that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.
Published: 2015
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42. First Measurement of the Polarization Observable E in the $\vec p(\vec \gamma,\pi^+)n$ Reaction up to 2.25 GeV

Author: Strauch, S., Briscoe, W. J., Döring, M., Klempt, E., Nikonov, V. A., Pasyuk, E., Rönchen, D., Sarantsev, A. V., Strakovsky, I., Workman, R., Adhikari, K. P., Adikaram, D., Anderson, M. D., Pereira, S. Anefalos, Anisovich, A. V., Badui, R. A., Ball, J., Batourine, V., Battaglieri, M., Bedlinskiy, I., Benmouna, N., Biselli, A. S., Brock, J., Brooks, W. K., Burkert, V. D., Cao, T., Carlin, C., Carman, D. S., Celentano, A., Chandavar, S., Charles, G., Colaneri, L., Cole, P. L., Compton, N., Contalbrigo, M., Cortes, O., Crede, V., Dashyan, N., D'Angelo, A., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Dugger, M., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Elouadrhiri, L., Eugenio, P., Fedotov, G., Fegan, S., Filippi, A., Fleming, J. A., Forest, T. A., Fradi, A., Gevorgyan, N., Ghandilyan, Y., Giovanetti, K. L., Girod, F. X., Glazier, D. I., Gohn, W., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guidal, M., Guo, L., Hafidi, K., Hakobyan, H., Hanretty, C., Harrison, N., Hattawy, M., Hicks, K., Ho, D., Holtrop, M., Hughes, S. M., Ilieva, Y., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Jiang, H., Jo, H. S., Joo, K., Joosten, S., Keith, C. D., Keller, D., Khachatryan, G., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F. J., Kubarovsky, V., Kuhn, S. E., Lenisa, P., Livingston, K., Lu, H. Y., MacGregor, I . J . D., Markov, N., McKinnon, B., Meekins, D. G., Meyer, C. A., Mokeev, V., Montgomery, R. A., Moody, C. I., Moutarde, H., Movsisyan, A, Munevar, E., Camacho, C. Munoz, Nadel-Turonski, P., Net, L. A., Niccolai, S., Niculescu, G., Niculescu, I., Osipenko, M., Ostrovidov, A. I., Park, K., Peng, P., Phelps, W., Phillips, J. J., Pisano, S., Pogorelko, O., Pozdniakov, S., Price, J. W., Procureur, S., Prok, Y., Protopopescu, D., Puckett, A. J. R., Raue, B. A., Ripani, M., Ritchie, B. G., Rizzo, A., Rosner, G., Roy, P., Sabatié, F., Salgado, C., Schott, D., Schumacher, R. A., Seder, E., Seely, M. L., Senderovich, I, Sharabian, Y. G., Simonyan, A., Skorodumina, Iu., Smith, G. D., Sober, D. I., Sokhan, D., Sparveris, N., Stoler, P., Stepanyan, S., Sytnik, V., Taiuti, M., Tian, Ye, Trivedi, A., Tucker, R., Ungaro, M., Voskanyan, H., Voutier, E., Walford, N. K., Watts, D. P., Wei, X., Wood, M. H., Zachariou, N., Zana, L., Zhang, J., Zhao, Z. W., and Zonta, I.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction $\vec \gamma \vec p \to \pi^+n$, has been measured using a circularly polarized tagged-photon beam, with energies from 0.35 to 2.37 GeV. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer in Hall B at the Thomas Jefferson National Accelerator Facility. These polarization data agree fairly well with previous partial-wave analyses at low photon energies. Over much of the covered energy range, however, significant deviations are observed, particularly in the high-energy region where high-L multipoles contribute. The data have been included in new multipole analyses resulting in updated nucleon resonance parameters. We report updated fits from the Bonn-Gatchina, J\"ulich, and SAID groups., Comment: 6 pages, 3 figures
Published: 2015
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43. Momentum sharing in imbalanced Fermi systems

Author: Hen, O., Sargsian, M., Weinstein, L. B., Piasetzky, E., Hakobyan, H., Higinbotham, D. W., Braverman, M., Brooks, W. K., Gilad, S., Adhikari, K. P., Arrington, J., Asryan, G., Avakian, H., Ball, J., Baltzell, N. A., Battaglieri, M., Beck, A., Beck, S. May-Tal, Bedlinskiy, I., Bertozzi, W., Biselli, A., Burkert, V. D., Cao, T., Carman, D. S., Celentano, A., Chandavar, S., Colaneri, L., Cole, P. L., Crede, V., DAngelo, A., De Vita, R., Deur, A., Djalali, C., Doughty, D., Dugger, M., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Elouadrhiri, L., Fedotov, G., Fegan, S., Forest, T., Garillon, B., Garcon, M., Gevorgyan, N., Ghandilyan, Y., Gilfoyle, G. P., Girod, F. X., Goetz, J. T., Gothe, R. W., Griffioen, K. A., Guidal, M., Guo, L., Hafidi, K., Hanretty, C., Hattawy, M., Hicks, K., Holtrop, M., Hyde, C. E., Ilieva, Y., Ireland, D. G., Ishkanov, B. I., Isupov, E. L., Jiang, H., Jo, H. S., Joo, K., Keller, D., Khandaker, M., Kim, A., Kim, W., Klein, F. J., Koirala, S., Korover, I., Kuhn, S. E., Kubarovsky, V., Lenisa, P., Levine, W. I., Livingston, K., Lowry, M., Lu, H. Y., MacGregor, I. J. D., Markov, N., Mayer, M., McKinnon, B., Mineeva, T., Mokeev, V., Movsisyan, A., Camacho, C. Munoz, Mustapha, B., Nadel-Turonski, P., Niccolai, S., Niculescu, G., Niculescu, I., Osipenko, M., Pappalardo, L. L., Paremuzyan, R., Park, K., Pasyuk, E., Phelps, W., Pisano, S., Pogorelko, O., Price, J. W., Procureur, S., Prok, Y., Protopopescu, D., Puckett, A. J. R., Rimal, D., Ripani, M., Ritchie, B. G., Rizzo, A., Rosner, G., Rossi, P., Roy, P., Sabatie, F., Schott, D., Schumacher, R. A., Sharabian, Y. G., Smith, G. D., Shneor, R., Sokhan, D., Stepanyan, S. S., Stepanyan, S., Stoler, P., Strauch, S., Sytnik, V., Taiuti, M., Tkachenko, S., Ungaro, M., Vlassov, A. V., Voutier, E., Watts, D., Walford, N. K., Wei, X., Wood, M. H., Wood, S. A., Zachariou, N., Zana, L., Zhao, Z. W., Zheng, X., and Zonta, I.
Subjects: Nuclear Experiment, Condensed Matter - Quantum Gases, Nuclear Theory
Abstract: The atomic nucleus is composed of two different kinds of fermions, protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority fermions (usually neutrons) to have a higher average momentum. Our high-energy electron scattering measurements using 12C, 27Al, 56Fe and 208Pb targets show that, even in heavy neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few body systems to neutron stars and may also be observable experimentally in two-spin state, ultra-cold atomic gas systems., Comment: Published in Science. 10 pages, 3 figures
Published: 2014
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44. A study of decays to strange final states with GlueX in Hall D using components of the BaBar DIRC

Author: The GlueX Collaboration, Dugger, M., Ritchie, B., Senderovich, I., Anassontzis, E., Ioannou, P., Kourkoumeli, C., Vasileiadis, G., Voulgaris, G., Jarvis, N., Levine, W., Mattione, P., McGinley, W., Meyer, C. A., Schumacher, R., Staib, M., Klein, F., Sober, D., Sparks, N., Walford, N., Doughty, D., Barnes, A., Jones, R., McIntyre, J., Mokaya, F., Pratt, B., Boeglin, W., Guo, L., Pooser, E., Reinhold, J., Ghoul, H. Al, Crede, V., Eugenio, P., Ostrovidov, A., Tsaris, A., Ireland, D., Livingston, K., Bennett, D., Bennett, J., Frye, J., Lara, M., Leckey, J., Mitchell, R., Moriya, K., Shepherd, M. R., Chernyshov, O., Dolgolenko, A., Gerasimov, A., Goryachev, V., Larin, I., Matveev, V., Tarasov, V., Barbosa, F., Chudakov, E., Dalton, M., Deur, A., Dudek, J., Egiyan, H., Furletov, S., Ito, M., Mack, D., Lawrence, D., McCaughan, M., Pennington, M., Pentchev, L., Qiang, Y., Smith, E., Somov, A., Taylor, S., Whitlatch, T., Zihlmann, B., Miskimen, R., Guegan, B., Hardin, J., Stevens, J., Williams, M., Berdnikov, V., Nigmatkulov, G., Ponosov, A., Romanov, D., Somov, S., Tolstukhin, I., Salgado, C., Ambrozewicz, P., Gasparian, A., Pedroni, R., Black, T., Gan, L., Dobbs, S., Seth, K., Ting, X., Tomaradze, A., Beattie, T., Huber, G., Lolos, G., Papandreou, Z., Semenov, A., Semenova, I., Brooks, W., Hakobyan, H., Kuleshov, S., Soto, O., Toro, A., Vega, I., Gevorgyan, N., and Kakoyan, V.
Subjects: Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract: We propose to enhance the kaon identification capabilities of the GlueX detector by constructing an FDIRC (Focusing Detection of Internally Reflected Cherenkov) detector utilizing the decommissioned BaBar DIRC components. The GlueX FDIRC would significantly enhance the GlueX physics program by allowing one to search for and study hybrid mesons decaying into kaon final states. Such systematic studies of kaon final states are essential for inferring the quark flavor content of hybrid and conventional mesons. The GlueX FDIRC would reuse one-third of the synthetic fused silica bars that were utilized in the BaBar DIRC. A new focussing photon camera, read out with large area photodetectors, would be developed. We propose operating the enhanced GlueX detector in Hall D for a total of 220 days at an average intensity of 5x10^7 {\gamma}/s, a program that was conditionally approved by PAC39, Comment: 25 pages, 29 figures
Published: 2014

45. A VLT/FLAMES survey for massive binaries in Westerlund 1. IV. Wd1-5 - binary product and a pre-supernova companion for the magnetar CXOU J1647-45?

Author: Clark, J. S., Ritchie, B. W., Najarro, F., Langer, N., and Negueruela, I.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: The first soft gamma-ray repeater was discovered over three decades ago, and subsequently identified as a magnetar. However there is currently no consenus on the formation channel(s) of these objects. The presence of a magnetar in the starburst cluster Westerlund 1 implies a >40Msun progenitor, favouring formation in a binary that was disrupted at supernova. To test this hypothesis we searched for the putative pre-SN companion via a radial velocity survey to identify high-velocity runaways, with subsequent atmospheric analysis of the resultant candidate, Wd1-5. Wd1-5 appears overluminous for its spectroscopic mass and we find evidence of He- and N-enrichment, O-depletion, and critically C-enrichment, a combination of properties that is difficult to explain for a single star. We infer a pre-SN history for Wd1-5 which supposes an initial close binary comprising two stars of comparable (~41Msun+35Msun) masses. Efficient mass transfer from the initially more massive component leads to the mass-gainer evolving more rapidly, initiating luminous blue variable/common envelope evolution. Reverse, wind-driven mass transfer during its subsequent WC Wolf-Rayet phase leads to the carbon pollution of Wd1-5, before a type Ibc supernova disrupts the binary system. Under the assumption of a physical association between Wd1-5 and J1647-45, the secondary is identified as the magnetar progenitor; its common envelope evolutionary phase prevents spin-down of its core prior to SN and the seed magnetic field for the magnetar forms either in this phase or during the earlier episode of mass transfer in which it was spun-up. Our results suggest that binarity is a key ingredient in the formation of at least a subset of magnetars by preventing spin-down via core-coupling and potentially generating a seed magnetic field., Comment: 17 pages, 10 figures, accepted for publication in Astronomy and Astrophysics
Published: 2014
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46. Exclusive ${\pi}^0$ electroproduction at $W>2$ GeV with CLAS

Author: Bedlinskiy, I., Kubarovsky, V., Niccolai, S., Stoler, P., Adhikari, K. P., Anderson, M. D., Pereira, S. Anefalos, Avakian, H., Ball, J., Baltzell, N. A., Battaglieri, M., Batourine, V., Biselli, A. S., Boiarinov, S., Bono, J., Briscoe, W. J., Brooks, W. K., Burkert, V. D., Carman, D. S., Celentano, A., Chandavar, S., Colaneri, L., Cole, P. L., Contalbrigo, M., Cortes, O., Crede, V., D'Angelo, A., Dashyan, N., De Vita, R., De Sanctis, E., Deur, A., Djalali, C., Doughty, D., Dupre, R., Egiyan, H., Alaoui, A. El, Fassi, L. El, Elouadrhiri, L., Eugenio, P., Fedotov, G., Fegan, S., Fleming, J. A., Forest, T. A., Garillon, B., Garçon, M., Gavalian, G., Gevorgyan, N., Ghandilyan, Y., Gilfoyle, G. P., Giovanetti, K. L., Girod, F. X., Golovatch, E., Gothe, R. W., Griffioen, K. A., Guegan, B., Guo, L., Hafidi, K., Hakobyan, H., Harrison, N., Hattawy, M., Hicks, K., Holtrop, M., Ireland, D. G., Ishkhanov, B. S., Isupov, E. L., Jenkins, D., Jo, H. S., Joo, K., Keller, D., Khandaker, M., Kim, A., Kim, W., Klein, A., Klein, F. J., Koirala, S., Kuhn, S. E., Kuleshov, S. V., Lenisa, P., Levine, W. I., Livingston, K., Lu, H. Y., MacGregor, I . J . D., Markov, N., Mayer, M., McKinnon, B., Mirazita, M., Mokeev, V., Montgomery, R. A., Moody, C. I., Moutarde, H., Movsisyan, A, Camacho, C. Munoz, Nadel-Turonski, P., Niculescu, I., Osipenko, M., Ostrovidov, A. I., Pappalardo, L. L., Park, K., Park, S., Pasyuk, E., Phelps, E., Phelps, W., Phillips, J. J., Pisano, S., Pogorelko, O., Price, J. W., Prok, Y., Protopopescu, D., Procureur, S., Puckett, A. J. R., Raue, B. A., Ripani, M., Ritchie, B. G., Rizzo, A., Rossi, P., Roy, P., Sabatié, F., Salgado, C., Schott, D., Schumacher, R. A., Seder, E., Senderovich, I., Sharabian, Y. G., Simonyan, A., Smith, G. D., Sober, D. I., Sokhan, D., Stepanyan, S. S., Strauch, S., Sytnik, V., Tang, W., Tian, Ye, Ungaro, M., Vlassov, A. V., Voskanyan, H., Voutier, E., Walford, N. K., Watts, D., Wei, X., Weinstein, L. B., Yurov, M., Zachariou, N., Zana, L., Zhang, J., Zhao, Z. W., and Zonta, I.
Subjects: Nuclear Experiment, High Energy Physics - Experiment
Abstract: Exclusive neutral-pion electroproduction ($ep\to e^\prime p^\prime \pi^0$) was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4\sigma/dtdQ^2dx_Bd\phi_\pi$ and structure functions $\sigma_T+\epsilon\sigma_L, \sigma_{TT}$ and $\sigma_{LT}$ as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. The data are compared with Regge and handbag theoretical calculations. Analyses in both frameworks find that a large dominance of transverse processes is necessary to explain the experimental results. For the Regge analysis it is found that the inclusion of vector meson rescattering processes is necessary to bring the magnitude of the calculated and measured structure functions into rough agreement. In the handbag framework, there are two independent calculations, both of which appear to roughly explain the magnitude of the structure functions in terms of transversity generalized parton distributions., Comment: 28 pages, 25 figures, Submitted to Phys. Rev. C
Published: 2014
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47. Histopathologic Changes, Ultrastructure, and Molecular Characterization of an Adenovirus in a Sun Conure ( Aratinga solstitialis )

Author: Gottdenker, N. L., Gregory, C. R., Ard, M. B., Lorenz, W. W., Nilsen, R. A., and Ritchie, B. W.
Published: 2019

48. The circumstellar environment and evolutionary state of the supergiant B[e] star Wd1-9

Author: Clark, J. S., Ritchie, B. W., and Negueruela, I.
Subjects: Astrophysics - Solar and Stellar Astrophysics
Abstract: The location of the supergiant (sg)B[e] star Wd1-9 within the coeval starburst cluster Westerlund 1 allows for its placement in a detailed post-Main Sequence evolutionary scheme and hence we have utilised a comprehensive multiwavelength dataset to determine its physical properties and relation to other sgB[e] stars and the evolved stellar population of Wd1. Wd1-9 is found to exhibit the rich optical emission line spectrum that is characteristic of sgB[e] stars, while dust mass, composition and disc geometry determined from mid-IR data resemble those of other well known examples such as R126. Extreme historical and ongoing mass loss is inferred from radio observations, while the X-ray properties of Wd1-9 imply the presence of high temperature plasma within the system and are directly comparable to a number of confirmed short-period colliding wind binaries within Wd1. The most complete explanation for the observational properties of Wd1-9 is that it is a massive interacting binary currently undergoing, or recently exited from, rapid Roche-lobe overflow, supporting the hypothesis that binarity mediates the formation of (a subset of) sgB[e] stars. The mass loss rate of Wd1-9 is consistent with such an assertion, while viable progenitor and descendent systems are present within Wd1 and other examples of sgB[e] binaries have previously been found. Moreover, the rarity of sgB[e] stars - only two examples are identified from a census of ~68 young massive Galactic clusters and associations containing ~600 post-Main Sequence stars - is explicable given the rapidity (~10^4yr) expected for this phase of massive binary evolution., Comment: 16 pages, 7 figures, accepted for publication in Astronomy and Astrophysics
Published: 2013
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49. Beam asymmetry for pi+ and pi0 photoproduction on the proton for photon energies from 1.102 to 1.862 GeV

Author: Dugger, M., Ritchie, B. G., Collins, P., Pasyuk, E., Briscoe, W. J., Strakovsky, I. I., Workman, R. L., and Azimov, Y.
Subjects: Nuclear Experiment
Abstract: Beam asymmetries for the reactions gamma p -> p pi0 and gamma p -> n pi+ have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged, linearly polarized photon beam with energies from 1.102 to 1.862 GeV. A Fourier moment technique for extracting beam asymmetries from experimental data is described. The results reported here possess greater precision and finer energy resolution than previous measurements. Our data for both pion reactions appear to favor the SAID and Bonn-Gatchina scattering analyses over the older Mainz MAID predictions. After incorporating the present set of beam asymmetries into the world database, exploratory fits made with the SAID analysis indicate that the largest changes from previous fits are for properties of the Delta(1700) 3/2- and Delta(1905) 5/2+ states., Comment: 24 pages 20 figures
Published: 2013
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50. An initial study of mesons and baryons containing strange quarks with GlueX

Author: The GlueX Collaboration, AlekSejevs, A., Barkanova, S., Dugger, M., Ritchie, B., Senderovich, I., Anassontzis, E., Ioannou, P., Kourkoumeli, C., Voulgaris, G., Jarvis, N., Levine, W., Mattione, P., McGinley, W., Meyer, C. A., Schumacher, R., Staib, M., Collins, P., Klein, F., Sober, D., Doughty, D., Barnes, A., Jones, R., McIntyre, J., Mokaya, F., Pratt, B., Boeglin, W., Guo, L., Khetarpal, P., Pooser, E., Reinhold, J., Ghoul, H. Al, Capstick, S., Crede, V., Eugenio, P., Ostrovidov, A., Sparks, N., Tsaris, A., Ireland, D., Livingston, K., Bennett, D., Bennett, J., Frye, J., Lara, M., Leckey, J., Mitchell, R., Moriya, K., Shepherd, M. R., Szczepaniak, A., Miskimen, R., Mushkarenkov, A., Guegan, B., Hardin, J., Stevens, J., Williams, M., Ponosov, A., Somov, S., Salgado, C., Ambrozewicz, P., Gasparian, A., Pedroni, R., Black, T., Gan, L., Dobbs, S., Seth, K. K., Tomaradze, A., Dudek, J., Close, F., Swanson, E., Denisov, S., Huber, G., Kolybaba, D., Krueger, S., Lolos, G., Papandreou, Z., Semenov, A., Semenova, I., Tahani, M., Brooks, W., Hakobyan, H., Kuleshov, S., Soto, O., Toro, A., Vega, I., White, R., Barbosa, F., Chudakov, E., Egiyan, H., Ito, M., Lawrence, D., McCaughan, M., Pennington, M., Pentchev, L., Qiang, Y., Smith, E. S., Somov, A., Taylor, S., Whitlatch, T., Wolin, E., and Zihlmann, B.
Subjects: Nuclear Experiment
Abstract: The primary motivation of the GlueX experiment is to search for and ultimately study the pattern of gluonic excitations in the meson spectrum produced in $\gamma p$ collisions. Recent lattice QCD calculations predict a rich spectrum of hybrid mesons that have both exotic and non-exotic $J^{PC}$, corresponding to $q\bar{q}$ states ($q=u,$ $d,$ or $s$) coupled with a gluonic field. A thorough study of the hybrid spectrum, including the identification of the isovector triplet, with charges 0 and $\pm1$, and both isoscalar members, $|s\bar{s}\ >$ and $|u\bar{u}\ > + |d\bar{d}\ >$, for each predicted hybrid combination of $J^{PC}$, may only be achieved by conducting a systematic amplitude analysis of many different hadronic final states. Detailed studies of the performance of the \gx detector have indicated that identification of particular final states with kaons is possible using the baseline detector configuration. The efficiency of kaon detection coupled with the relatively lower production cross section for particles containing hidden strangeness will require a high intensity run in order for analyses of such states to be feasible. We propose to collect a total of 200 days of physics analysis data at an average intensity of $5\times 10^7$ tagged photons on target per second. This data sample will provide an order of magnitude statistical improvement over the initial GlueX running, which will allow us to begin a program of studying mesons and baryons containing strange quarks. In addition, the increased intensity will permit us to study reactions that may have been statistically limited in the initial phases of GlueX. Overall, this will lead to a significant increase in the potential for \gx to make key experimental advances in our knowledge of hybrid mesons and excited $\Xi$ baryons., Comment: 22 pages, 8 figures
Published: 2013

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