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48 results on '"Sarty A"'

1. Deeply virtual Compton scattering cross section at high Bjorken x_{B}

Author

Georges, F, Rashad, M. N. H., Stefanko, A, Dlamini, M, Karki, B, Ali, S. F., Lin, P-J, Ko, H-S, Israel, N, Adikaram, D, Ahmed, Z, Albataineh, H, Aljawrneh, B, Allada, K, Allison, S, Alsalmi, S, Androic, D, Aniol, K, Annand, John, Atac, H, Averett, T, Ayerbe Gayoso, C, Bai, X, Bane, J, Barcus, S, Bartlett, K, Bellini, V, Beminiwattha, R, Bericic, J, Biswas, D, Brash, E, Bulumulla, D, Campbell, J, Camsonne, A, Carmignotto, M, Castellano, J, Chen, C, Chen, J-P, Chetry, T, Christy, M. E., Cisbani, E, Clary, B, Cohen, E, Compton, N, Cornejo, J. C., Covrig Dusa, S, Crowe, B, Danagoulian, S, Danley, T, De Persio, F, Deconinck, W, Defurne, M, Desnault, C, Di, D, Duer, M, Duran, B, Ent, R, Fanelli, C, Franklin, G, Fuchey, E, Gal, C, Gaskell, D, Gautam, T, Glamazdin, O, Gnanvo, K, Gray, V. M., Gu, C, Hague, T, Hamad, G, Hamilton, David, Hamilton, K., Hansen, O, Hauenstein, F, Henry, W, Higinbotham, D. W., Holmstrom, T, Horn, T, Huang, Y, Huber, G. M., Hyde, C. E., Ibrahim, H, Jen, C-M, Jin, K, Jones, M, Kabir, A, Keppel, C, Khachatryan, V, King, P. M., Li, S, Li, W. B., Liu, J, Liu, H, Liyanage, A, Magee, J, Malace, S, Mammei, J, Markowitz, P, McClellan, E, Mazouz, M, Meddi, F, Meekins, D, Mesik, K, Michaels, R, Mkrtchyan, A, Montgomery, Rachel, Muñoz Camacho, C, Myers, L. S., Nadel-Turonski, P, Nazeer, S. J., Nelyubin, V, Nguyen, D, Nuruzzaman, N, Nycz, M, Obretch, O. F., Ou, L, Palatchi, C, Pandey, B, Park, S, Park, K, Peng, C, Pomatsalyuk, R, Pooser, E, Puckett, A. J. R., Punjabi, V, Quinn, B, Rahman, S, Reimer, P. E., Roche, J, Sapkota, I, Sarty, A, Sawatzky, B, Saylor, N. H., Schmookler, B, Shabestari, M. H., Shahinyan, A, Sirca, S, Smith, G. R., Sooriyaarachchilage, S, Sparveris, N, Spies, R, Su, T, Subedi, A, Sulkosky, V, Sun, A, Thorne, L, Tian, Y, Ton, N, Tortorici, F, Trotta, R, Urciuoli, G. M., Voutier, E, Waidyawansa, B, Wang, Y, Wojtsekhowski, B, Wood, S, Yan, X, Ye, L, Ye, Z, Yero, C, Zhang, J, Zhao, Y, Zhu, P, and Jefferson Lab Hall A Collaboration

Abstract

We report high-precision measurements of the deeply virtual Compton scattering (DVCS) cross section at high values of the Bjorken variable x_{B}. DVCS is sensitive to the generalized parton distributions of the nucleon, which provide a three-dimensional description of its internal constituents. Using the exact analytic expression of the DVCS cross section for all possible polarization states of the initial and final electron and nucleon, and final state photon, we present the first experimental extraction of all four helicity-conserving Compton form factors (CFFs) of the nucleon as a function of x_{B}, while systematically including helicity flip amplitudes. In particular, the high accuracy of the present data demonstrates sensitivity to some very poorly known CFFs.

Published
2022

2. Helicity-dependent cross sections for the photoproduction of π0 pairs from nucleons

Author

Dieterle, M., Witthauer, L., Fix, A., Abt, S., Achenbach, P., Adlarson, P., Afzal, F., Bartolome, P. Aguar, Ahmed, Z., Annand, J. R. M., Arends, H. J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N., Braghieri, A., Briscoe, W. J., Cividini, F., Collicott, C., Costanza, S., Denig, A., Dolzhikov, A. S., Downie, E. J., Drexler, P., Gardner, S., Ghosal, D., Glazier, D. I., Gorodnov, I., Gradl, W., G{ü, M., nther, Gurevich, D., Heijkenskj{ö, L., Hornidge, D., Huber, G. M., K{ä, A., ser, Kashevarov, V. L., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A., Lisin, V., Livingston, K., Lutterer, S., MacGregor, I. J. D., Manley, D. M., Martel, P. P., Metag, V., Meyer, W., Middleton, D. G., Miskimen, R., Mornacchi, E., Mullen, C., Mushkarenkov, A., Neganov, A., Neiser, A., Oberle, M., Ostrick, M., Otte, P. B., Paudyal, D., Pedroni, P., Polonski, A., Powell, A., Prakhov, S. N., Reicherz, G., Ron, G., Rostomyan, T., Sarty, A., Sfienti, C., Sokhoyan, V., Spieker, K., Steffen, O., Strakovsky, I. I., Strub, T., Supek, I., Thiel, A., Thiel, M., Thomas, A., Unverzagt, M., Usov, Yu. A., Wagner, S., Walford, N. K., Watts, D. P., Werthmüller, D., Wettig, J., Wolfes, M., and Zana, L. A.

Subjects
Physics, Proton, spin polarization, neutron, photodisintegration, Crystal Ball at MAMI, Nuclear Theory, Bremsstrahlung, General Physics and Astronomy, Electron, 7. Clean energy, 01 natural sciences, Resonance (particle physics), Helicity, Nuclear physics, 0103 physical sciences, Neutron, 010306 general physics, Nucleon, Nuclear Experiment, Crystal Ball
Abstract

The double-polarization observable $E$ and helicity-dependent cross sections $\sigma_{1/2}$, $\sigma_{3/2}$ have been measured for the photoproduction of $\pi^0$ pairs off quasi-free protons and neutrons at the Mainz MAMI accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost $4\pi$ covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the $\gamma N\rightarrow N\pi^0\pi^0$ reaction. They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. The comparison of the prediction and the refit demonstrate the large impact of the new data., Comment: Submitted to Phys. Rev. Lett

Published
2020

3. Signatures of the d*(2380) Hexaquark in d(γ,pn→)

Author

Bashkanov, M., Watts, D. P., Kay, S. J. D., Abt, S., Achenbach, P., Adlarson, P., Afzal, F., Ahmed, Z., Akondi, C. S., Annand, J. R. M., Arends, H. J., Beck, R., Biroth, M., Borisov, N., Braghieri, A., Briscoe, W. J., Cividini, F., Collicott, C., Costanza, S., Denig, A., Downie, E. J., Drexler, P., Fegan, S., Fix, A., Gardner, S., Ghosal, D., Glazier, D. I., Gorodnov, I., Gradl, W., Günther, M., Gurevich, D., Heijkenskjöld, L., Hornidge, D., Huber, G. M., Käser, A., Kashevarov, V. L., Korolija, M., Krusche, B., Lazarev, A., Livingston, K., Lutterer, S., MacGregor, I. J. D., Manley, D. M., Martel, P. P., Miskimen, R., Mornacchi, E., Mullen, C., Neganov, A., Neiser, A., Ostrick, M., Otte, P. B., Paudyal, D., Pedroni, P., Powell, A., Prakhov, S. N., Ron, G., Sarty, A., Sfienti, C., Sokhoyan, V., Spieker, K., Steffen, O., Strakovsky, I. I., Strub, T., Supek, I., Thiel, A., Thiel, M., Thomas, A., Usov, Yu. A., Wagner, S., Walford, N. K., Werthmüller, D., Wettig, J., Wolfes, M., Zachariou, N., and Zana, L. A.

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured photon energy range of 300–700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around \ud E\ud γ\ud ∼\ud 570\ud \ud \ud MeV\ud is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behavior could be related to the excitation of the \ud d\ud ∗\ud (\ud 2380\ud )\ud hexaquark.

Published
2020

4. Cross section for γn→π0n measured at the Mainz A2 experiment

Author

Briscoe, W. J., Hadžimehmedović, M., Kudryavtsev, A. E., Kulikov, V. V., Martemianov, M. A., Strakovsky, I. I., Švarc, Alfred, Tarasov, V. E., Workman, R. L., Abt, S., Achenbach, P., Akondi, C. S., Afzal, F., Aguar-Bartolomé, P., Ahmed, Z., Annand, J. R. M., Arends, H. J., Bantawa, K., Bashkanov, M., Beck, R., Biroth, M., Borisov, N., Braghieri, A., Bulychjov, S. A., Cividini, F., Collicott, C., Costanza, S., Denig, A., Downie, E. J., Drexler, P., Fegan, S., Ferretti Bondy, M. I., Gardner, S., Ghosal, D., Glazier, D. I., Gorodnov, I., Gradl, W., Günther, M., Gurevich, D., Heijkenskjöld, L., Hornidge, D., Huber, G. M., Käser, A., Kashevarov, V. L., Kay, S., Korolija, Milorad, Krusche, B., Lazarev, A., Livingston, K., Lutterer, S., MacGregor, I. J. D., Macrae, R., Manley, D. M., Martel, P. P., McGeorge, J. C., Middleton, D. G., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Mullen, C., Neganov, A., Neiser, A., Ostrick, M., Otte, P. B., Osmanović, H., Omerović, R., Oussena, B., Paudyal, D., Pedroni, P., Powell, A., Prakhov, S. N., Ron, G., Rostomyan, T., Sarty, A., Sfienti, C., Sokhoyan, V., Spieker, K., Stahov, J., Steffen, O., Supek, Ivan, Thiel, A., Thiel, M., Thomas, A., Tiator, L., Unverzagt, M., Usov, Yu. A., Walford, N. K., Watts, D. P., Wagner, S., Werthmüller, D., Wettig, J., Wolfes, M., and Zachariou, N.

Subjects
Physics, Nuclear Theory, neutral pion-photoproduction, tagged photon spectrometer, microtron, Nuclear Experiment
Abstract

The gamma n -> pi(0)n differential cross section evaluated for 27 energy bins span the photon-energy range 290-813 MeV (W = 1.195- 1.553 GeV) and the pion c.m. polar production angles, ranging from 18 degrees to 162 degrees, making use of model-dependent nuclear corrections to extract pi(0) production data on the neutron from measurements on the deuteron target. Additionally, the total photoabsorption cross section was measured. The tagged photon beam produced by the 883 MeV electron beam of the Mainz Microtron MAMI was used for the pi(0)-meson production. Our accumulation of 3.6 x 10(6) gamma n -> pi(0)n events allowed a detailed study of the reaction dynamics. Our data are in reasonable agreement with previous A2 measurements and extend them to lower energies. The data are compared with predictions of previous SAID, MAID, and BnGa partial-wave analyses and to the latest SAID fit MA19 that included our data. Selected photon-decay amplitudes N* -> gamma n at the resonance poles are determined for the first time.

Published
2019

5. High-statistics measurement of the η → 3π0 decay at MAMI

Author

Prakhov, S., Abt, S., Adlarson, P., Afzal, F., Aguar-Bartolome, P., Ahmed, |., Ahrens, J., Annand, J.R.M., Arends, H.J., Bantawa, K., Bashkanov, M., Beck, R., Biroth, M., Borisov, N.S., Braghieri, A., Briscoe, W.J., Cherepnya, S., Cividini, F., Collicott, C., Costanza, S., Denig, A., Dieterle, M., Downie, E.J., Drexler, P., Ferretti Bondy, M.I., Fil'kov, L.V., Fix, A., Gardner, S., Garni, S., Glazier, D.I., Gordonov, I., Gradl, W., Gurevich, G.M., Heijkenskjöld, L., Hornidge, D., Huber, G.M., Käser, A., Kashevarov, V.L., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A., Lisin, V., Livingston, K., Lutterer, S., MacGregor, I.J.D., Manley, D.M., Martel, P.P., McGeorge, J.C., Middleton, D.G., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Neganov, A., Neiser, A., Oberle, M., Ostrick, M., Otte, P.B., Paudyal, D., Pedroni, P., Polonski, A., Ron, G., Rostomyan, T., Sarty, A., Sfienti, C., Sokhoyan, V., Spieker, K., Steffen, O., Strakovsky, I.I., Strandberg, B., Strub, Th., Supek, I., Thiel, A., Thiel, M., Thomas, A., Unverzagt, M., Usov, Yu. A., Wagner, S., Walford, N.K., Watts, D.P., Werthmüller, D., Wettig, J., Witthauer, L., Wolfes, M., and Zana, L.A.

Abstract

The largest, at the moment, statistics of 7×106 η→3π0 decay s, based on 6.2×107 η mesons produced in the γp→ηp r eaction, has been accumulated by the A2 Collaboration at the Mainz Microtron, MAMI. It allowed a detailed study of the η→3π0 dynamics beyond its conventional parametrization with just the quadratic slope parameter α and enabled, for the first time, a measurement of the second-order ter m and a better understanding of the cusp structure in the neutral decay. The present data are also compared to recent theoretical calculations that predict a nonlinear dependence along the quadratic distance from the Dalitz-plot center.

Published
2018

6. Helicity-dependent cross sections and double-polarization observable E in η photoproduction\ud from quasifree protons and neutrons

Author

Witthauer, L., Dieterle, M., Abt, S., Achenbach, P., Afzal, F., Ahmed, Z., Akondi, C.S., Annand, J.R.M., Arends, H.J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N.S., Braghieri, A., Briscoe, W.J., Cividini, F., Costanza, S., Collicott, C., Denig, A., Downie, E.J., Drexler, P., Ferretti-Bondy, M.I., Gardner, S., Garni, S., Glazier, D.I., Glowa, D., Gradl, W., Günther, M., Gurevich, G.M., Hamilton, D., Hornidge, D., Huber, G.M., Käser, A., Kashevarov, V.L., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A.B., Linturi, J.M., Lisin, V., Livingston, K., Lutterer, S., MacGregor, I.J.D., Mancell, J., Manley, D.M., Martel, P.P., Metag, V., Meyer, W., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Neganov, A.B., Neiser, A., Oberle, M., Ostrick, M., Otte, P.B., Paudyal, D., Pedroni, P., Polonski, A., Prakhov, S.N., Rajabi, A., Reicherz, G., Ron, G., Rostomyan, T., Sarty, A., Sfienti, C., Sikora, M.H., Sokhoyan, V., Spieker, K., Steffen, O., Strakovsky, I.I., Strub, Th., Supek, I., Thiel, A., Thiel, M., Thomas, A., Unverzagt, M., Usov, Yu A., Wagner, S., Walford, N.K., Watts, D.P., Werthmüller, D., Wettig, J., Wolfes, M., and Zana, L.

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

Precise helicity-dependent cross sections and the double-polarization observable E were measured for η\ud photoproduction from quasifree protons and neutrons bound in the deuteron. The η → 2γ and η → 3π0 → 6γ\ud decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The\ud measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz.\ud A longitudinally polarized deuterated butanol target was used in combination with a circularly polarized photon\ud beam from bremsstrahlung of a longitudinally polarized electron beam. The reaction products were detected with\ud the electromagnetic calorimeters Crystal Ball and TAPS, which covered 98% of the full solid angle. The results\ud show that the narrow structure observed earlier in the unpolarized excitation function of η photoproduction off\ud the neutron appears only in reactions with antiparallel photon and nucleon spin (σ1/2). It is absent for reactions\ud with parallel spin orientation (σ3/2) and thus very probably related to partial waves with total spin 1/2. The\ud behavior of the angular distributions of the helicity-dependent cross sections was analyzed by fitting them with Legendre polynomials. The results are in good agreement with a model from the Bonn-Gatchina group, which\ud uses an interference of P11 and S11 partial waves to explain the narrow structure.

Published
2017

7. Study of η and η' Photoproduction at MAMI

Author

Kashevarov, V.L., Ott, P., Prakhov, S., Adlarson, P., Afzal, F., Ahmed, Z., Akondi, C.S., Annand, J.R.M., Arends, H.J., Beck, R., Braghieri, A., Briscoe, W.J., Cividini, F., Codling, R., Collicott, C., Costanza, S., Denig, A., Downie, E.J., Dieterle, M., Ferretti Bondy, M.I., Filkov, L.V., Fix, A., Gardner, S., Garni, S., Glazier, D.I., Glowa, D., Gradl, W., Gurevich, G., Hamilton, D.J., Hornidge, D., Howdle, D., Huber, G.M., Käser, A., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Linturi, J., Lisin, V., Livingston, K., MacGregor, I.J.D., MacRae, R., Mancell, J., Manley, D.M., Martel, P.P., McGeorge, J.C., McNicol, E., Middleton, D.G., Miskimen, R., Mornacchi, E., Mullen, C., Mushkarenkov, A., Neiser, A., Oberle, M., Ostrick, M., Otte, P.B., Oussena, B., Paudyal, D., Pedroni, P., Polyanski, V.V., Rajabi, A., Reicherz, G., Robinson, J., Rosner, G., Rostomyan, T., Sarty, A., Schott, D.M., Schumann, S., Sfienti, C., Sokhoyan, V., Spieker, K., Steffen, O., Strandberg, B., Strakovsky, I.I., Strub, Th., Supek, I., Taragin, M.F., Thiel, A., Thiel, M., Tiator, L., Thomas, A., Unverzagt, M., Wagner, S., Watts, D.P., Werthmüller, D., Wettig, J., Witthauer, L., Wolfes, M., Workman, R.L., and Zana, L.

Subjects
ddc:550
Abstract

The reactions γp → ηp and γp → η0\ud p are measured from their thresholds up to the center-of-mass\ud energy W ¼ 1.96 GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross\ud sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full\ud production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the\ud energies in the vicinity of the η0 threshold, W ¼ 1896 MeV (Eγ ¼ 1447 MeV). Within the framework of a\ud revised ηMAID isobar model, the cusp, in connection with a steep rise of the η0 total cross section from its\ud threshold, can only be explained by a strong coupling of the poorly known Nð1895Þ1=2− state to both ηp\ud and η0\ud p. Including the new high-accuracy results in the ηMAID fit to available η and η0 photoproduction\ud data allows the determination of the Nð1895Þ1=2− properties.

Published
2017
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8. Insight into the narrow structure in η-photoproduction on the neutron from helicity\ud dependent cross sections

Author

Witthauer, L., Dieterle, M., Abt, S., Achenbach, P., Afzal, F, Ahmed, Z., Annand, J.R.M., Arends, H.J., Bashkanov, M, Beck, R., Biroth, M., Borisov, N.S., Braghieri, A., Briscoe, W.J., Cividini, F., Costanza, S., Collicott, C., Denig, A., Downie, E.J., Drexler, P., Ferretti-Bondy, M.I., Gardner, S., Garni, S., Glazier, D.I., Glowa, D., Gradl, W., Günther, M., Gurevich, G.M., Hamilton, D., Hornidge, D., Huber, G.M., Käser, A., Kashevarov, V.L., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A.B., Linturi, J.M., Lisin, V., Livingston, K., Lutterer, S., MacGregor, I.J.D., Mancell, J., Manley, D.M., Martel, P.P., Metag, V., Meyer, W., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Neganov, A.B., Neiser, A., Oberle, M., Ostrick, M., Otte, P.B., Paudyal, D., Pedroni, P., Polonski, A., Prakhov, S.N., Rajabi, A., Reicherz, G., Ron, G, Rostomyan, T., Sarty, A., Sfienti, C., Sikora, M.H., Sokhoyan, V., Spieker, K., Steffen, O., Strakovski, I.I., Strub, Th., Supek, I., Thiel, A., Thiel, M., Thomas, A., Unverzagt, M., Usov, Yu. A., Wagner, S., Walford, N.K., Watts, D.P., Werthmüller, D., Wettig, J., Wolfes, M., and Zana, L.

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

The double polarization observable E and the helicity dependent cross sections σ1/2 and σ3/2 were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π0. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ1/2 and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N1/2− (S11) and N 1/2+ (P11). Furthermore, the extracted Legendre coefficients of the angular distributions for σ1/2 are in good agreement with recent reaction model predictions assuming a narrow resonance in the P11 wave as the origin of this structure.

Published
2016

9. Insight into the Narrow Structure in eta Photoproduction on the Neutron from Helicity-Dependent Cross Sections

Author

Witthauer, L., Dieterle, M., Achenbach, S., Afzal, F., Ahmed, Z., Annand, J. R. M., Arends, H. J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N. S., Braghieri, A., Briscoe, W. J., Cividini, F., Costanza, S., Collicott, C., Denig, A., Downie, E. J., Drexler, P., Ferretti-Bondy, M. I., Gardner, S., Garni, S., Glazier, D. I., Glowa, D., Gradl, W., Gunther, M., Gurevich, G. M., Hamilton, D., Hornidge, D., Huber, G. M., Kaser, A., Kashevarov, V. L., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A. B., Linturi, J. M., Lisin, V., Livingston, K., Lutterer, S., MacGregor, I. J. D., Mancell, J., Manley, D. M., Martel, P. P., Metag, V., Meyer, W., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Neganov, A. B., Neiser, A., Oberle, M., Ostrick, M., Otte, P. B., Paudyal, D., Pedroni, P., Polonski, A., Prakhov, S. N., Rajabi, A., Reicherz, G., Ron, G., Rostomyan, T., Sarty, A., Sfienti, C., Sikora, M. H., Sokhoyan, V., Spieker, K., Steffen, O., Strakovski, I. I., Strub, Th., Supek, I., Thiel, A., Thiel, M., Thomas, A., Unverzagt, M., Usov, Yu. A., Wagner, S., Walford, N. K., Watts, D. P., Werthmuller, D., Wettig, J., Wolfes, M., Zana, L., and Abt, P.

Subjects
Nuclear Theory, Nuclear Experiment
Abstract

The double polarization observable E and the helicity dependent cross sections σ1/2 and σ3/2 were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π0. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ1/2 and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N1/2− (S11) and N 1/2+ (P11). Furthermore, the extracted Legendre coefficients of the angular distributions for σ1/2 are in good agreement with recent reaction model predictions assuming a narrow resonance in the P11 wave as the origin of this structure.

Published
2016
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10. T and F asymmetries in π0 photoproduction on the proton

Author

Annand, J.R.M., Arends, H.J., Beck, R., Borisov, N., Braghieri, A., Briscoe, W.J., Cherepnya, S., Collicott, C., Costanza, S., Downie, E.J., Dieterle, M., Fix, A., Fil'kov, L.V., Garni, S., Glazier, D.I., Gradl, W., Gurevich, G., Hall Barrientos, P., Hamilton, D., Hornidge, D., Howdle, D., Huber, G.M., Kashevarov, V.L., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A., Lisin, V., Livingston, K., MacGregor, I.J.D., Mancel, J., Manley, D.M., Martel, P.P., McNicoll, E.F., Meyer, W., Middleton, D.G., Miskimen, R., Mushkarenkov, A., Neganov, A., Nikolaev, A., Oberle, M., Ortega, H., Ostrick, M., Ott, P., Otte, P.B., Oussena, B., Pedroni, P., Polonski, A., Polyanski, V.V., Prakhov, S., Reicherz, G., Rostomyan, T., Sarty, A., Schumann, S., Steffen, O., Strakovsky, I.I., Strub, Th., Supek, I., Tiator, L., Thomas, A., Unverzagt, M., Usov, Yu.A., Watts, D.P., Werthmüller, D., Witthauer, L., Wolfes, M., and Ortega Spina, Henry G. Universidad de la República (Uruguay). Facultad de Ciencias. Instituto de Física

Subjects
Photoproduction, Physics::Accelerator Physics, Nuclear Experiment, Resonance, Η photoproduction, QC
Abstract

The γp→π0p reaction was studied at laboratory photon energies from 425 to 1445 MeV with a transversely polarized target and a longitudinally polarized beam. The beam-target asymmetry F was measured for the first time and new high precision data for the target asymmetry T were obtained. The experiment was performed at the photon tagging facility of the Mainz Microtron (MAMI) using the Crystal Ball and TAPS photon spectrometers. The polarized cross sections were expanded in terms of associated Legendre functions and compared to recent predictions from several partial-wave analyses. The impact of the new data on our understanding of the underlying partial-wave amplitudes and baryon resonance contributions is discussed.

Published
2016

11. Measurement of π0 photoproduction on the proton at MAMI C

Author

Adlarson, P., Afzal, F., Akondi, C. S., Annand, J. R. M., Arends, H. J., Azimov, Ya. I., Beck, R., Borisov, N., Braghieri, A., Briscoe, W. J., Cherepnya, S., Cividini, F., Collicott, C., Costanza, S., Denig, A., Downie, E. J., Dieterle, M., Ferretti Bondy, M. I., Fil'kov, L. V., Fix, A., Gardner, S., Garni, S., Glazier, D. I., Glowa, D., Gradl, W., Gurevich, G., Hamilton, D. J., Hornidge, D., Huber, G. M., Käser, A., Kashevarov, V. L., Kay, S., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Kulikov, V. V., Lazarev, A., Linturi, J., Lisin, V., Livingston, K., MacGregor, I. J. D., Manley, D. M., Martel, P. P., Martemianov, M., McGeorge, J. C., Meyer, W., Middleton, D. G., Miskimen, R., Mushkarenkov, A., Neganov, A., Neiser, A., Oberle, M., Ostrick, M., Ott, P., Otte, P. B., Oussena, B., Paudyal, D., Pedroni, P., Polonski, A., Polyanski, V. V., Prakhov, S., Rajabi, A., Reicherz, G., Ron, G., Rostomyan, T., Sarty, A., Schott, D. M., Schumann, S., Sfienti, C., Sokhoyan, V., Spieker, K., Steffen, O., Strakovsky, I. I., Strub, Th., Supek, I., Taragin, M. F., Thiel, A., Thiel, M., Tiator, L., Thomas, A., Unverzagt, M., Usov, Yu. A., Wagner, S., Watts, D. P., Werthmüller, D., Wettig, J., Witthauer, L., Wolfes, M., Workman, R. L., and Zana, L. A.

Subjects
Nuclear Experiment
Abstract

Differential cross sections for the γp→π0p reaction have been measured with the A2 tagged-photon facilities at the Mainz Microtron, MAMI C, up to the center-of-mass energy W=1.9GeV. The new results, obtained with a fine energy and angular binning, increase the existing quantity of π0 photoproduction data by ∼47%. Owing to the unprecedented statistical accuracy and the full angular coverage, the results are sensitive to high partial-wave amplitudes. This is demonstrated by the decomposition of the differential cross sections in terms of Legendre polynomials and by further comparison to model predictions. A new solution of the SAID partial-wave analysis obtained after adding the new data into the fit is presented.

Published
2015

12. First measurement of target and beam-target asymmetries in the γp→π0ηp reaction

Author

Annand, J.R.M., Arends, H. J., Beck, R., Borisov, N., Braghieri, A., Briscoe, W. J., Cherepnya, S., Collicott, C., Costanza, S., Downie, E. J., Dieterle, M., Fix, A., Fil'kov, L. V., Garni, S., Glazier, D.I., Gradl, W., Gurevich, G., Hall Barrientos, P., Hamilton, D., Hornidge, D., Howdle, D., Huber, G. M., Kashevarov, V. L., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lazarev, A., Lisin, V., Livingston, K., MacGregor, I. J. D., Mancel, J., Manley, D. M., Martel, P. P., McNicoll, E. F., Meyer, W., Middleton, D. G., Miskimen, R., Mushkarenkov, A., Neganov, A., Nikolaev, A., Oberle, M., Ortega, H., Ostrick, M., Ott, P., Otte, P. B., Oussena, B., Pedroni, P., Polonski, A., Polyanski, V. V., Prakhov, S., Reicherz, G., Rostomyan, T., Sarty, A., Schumann, S., Steffen, O., Strakovsky, I. I., Strub, Th., Supek, I., Tiator, L., Thomas, A., Unverzagt, M., Usov, Yu. A., Watts, D. P., Werthmüller, D., Witthauer, L., and Wolfes, M.

Subjects
Physics::Accelerator Physics, Nuclear Experiment
Abstract

The first data on target and beam-target asymmetries for the γp→π0ηp reaction at photon energies from 1050 up to 1450 MeV are presented. The measurements were performed using the Crystal Ball and TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. The general assumption that the reaction is dominated by the Δ3/2− amplitude is confirmed. The data are in particular sensitive to small contributions from other partial waves.

Published
2015

13. High energy angular distribution measurements of the exclusive deuteron photodisintegration reaction

Author

K. Benslama, B. D. Fox, R. I. Pomatsalyuk, J. O. Hansen, Arijit Saha, Olivier Gayou, P. Bosted, Bogdan Wojtsekhowski, S. Dumalski, P. E. Ulmer, D. J. Margaziotis, E. Chudakov, Nilanga Liyanage, G. J. Kumbartzki, D. Crovelli, C. Glashausser, J. Calarco, A. J. Sarty, R. A. Lindgren, Kevin Fissum, S. Churchwell, S. Malov, V. Gorbenko, E. J. Brash, R. J. Holt, C. W. de Jager, C. E. Jones, K. A. Aniol, K. McCormick, K. Wijesooriya, C. F. Perdrisat, John C. Mitchell, W. Xu, M. K. Jones, J. Hovdebo, J. Gomez, Daniel Simon, C. C. Chang, Dipangkar Dutta, R. Suleiman, F. Xiong, L. Todor, Jian-Ping Chen, Sonja Dieterich, R. Roche, Ronald Ransome, R. Michaels, Anatoly Radyushkin, F. Garibaldi, J. Gao, S. Becher, G. M. Huber, James J. Kelly, M. B. Epstein, M. Amarian, G. M. Urciuoli, T. Chang, M. Liang, J. LeRose, E. R. Kinney, Haiyan Gao, M Rvachev, D. Meekins, M. Kuss, V. A. Punjabi, X. Jiang, E. Schulte, L. Bimbot, Seonho Choi, L. Morand, S. Frullani, Ronald Gilman, A. V. Glamazdin, Z. Chai, Andrei Afanasev, S. Strauch, P. Markowitz, Edgar E. Kooijman, and Z. E. Meziani

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Photon, media_common.quotation_subject, Nuclear Theory, Particle accelerator, Acceleratorfysik och instrumentering, Accelerator Physics and Instrumentation, String (physics), Asymmetry, law.invention, Nuclear physics, Amplitude, Angular distribution, Deuterium, Photodisintegration, law, High Energy Physics::Experiment, Nuclear Experiment, media_common
Abstract

The first complete measurements of the angular distributions of the two-body deuteron photodisintegration differential cross section at photon energies above 1.6 GeV were performed at the Thomas Jefferson National Accelerator Facility. The results show a persistent forward-backward asymmetry up to Eγ = 2.4 GeV, the highest-energy measured in this experiment. The Hard Rescattering and the Quark-Gluon string models are in fair agreement with the results.

Published
2002

14. Determination of the Pion Charge Form Factor at Q2=1.60 and 2.45 (GeV/c)2

Author

Horn, D.T., Horn, D.T., Aniol, K., Arrington, J., Barret, B., Beise, E.J., Blok, H.P., Boeglin, W., Brash, E.J., Breuer, H., Chang, C.C., Christy, M.E., Ent, R., Gaskell, D., Gibson, E., Holt, R.J., Huber, G.M., Jin, S., Jones, M.K., Keppel, C.E., Kim, W., King, P.M., Kovaltchouk, V., Liu, J., Lolos, G.J., Mack, D.J., Margaziotis, D.J., Markowitz, P., Matsumura, A., Meekins, D., Miyoshi, T., Mkrtchyan, H., Niculescu, I., Okayasu, Y., Pentchev, L., Perdrisat, C., Potterveld, D., Punjabi, V., Reimer, P., Reinhold, J., Roche, J., Roos, P.G., Sarty, A., Smith, G.R., Tadevosyan, V., Tang, L.G., Tvaskis, V., Vidakovic, S., Volmer, J., Vulcan, W., Warren, G., Wood, S.A., Xu, C., X. Zheng, X., Jefferson Lab F_{π} Collaboration, Horn, D.T., Horn, D.T., Aniol, K., Arrington, J., Barret, B., Beise, E.J., Blok, H.P., Boeglin, W., Brash, E.J., Breuer, H., Chang, C.C., Christy, M.E., Ent, R., Gaskell, D., Gibson, E., Holt, R.J., Huber, G.M., Jin, S., Jones, M.K., Keppel, C.E., Kim, W., King, P.M., Kovaltchouk, V., Liu, J., Lolos, G.J., Mack, D.J., Margaziotis, D.J., Markowitz, P., Matsumura, A., Meekins, D., Miyoshi, T., Mkrtchyan, H., Niculescu, I., Okayasu, Y., Pentchev, L., Perdrisat, C., Potterveld, D., Punjabi, V., Reimer, P., Reinhold, J., Roche, J., Roos, P.G., Sarty, A., Smith, G.R., Tadevosyan, V., Tang, L.G., Tvaskis, V., Vidakovic, S., Volmer, J., Vulcan, W., Warren, G., Wood, S.A., Xu, C., X. Zheng, X., and Jefferson Lab F_{π} Collaboration

Abstract

The 1H(e,e′π+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (Fπ) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which Fπ is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative quantum chromodynamics prediction.

Published
2006

15. Recoil Polarization for Δ Excitation in Pion Electroproduction

Author

Kelly, J.J., Kelly, J.J., Roche, R.E., Chai, Z., Jones, M.K., Gayou, O., Sarty, A.J., Frullani, S., Aniol, K., Beise, E.J., Benmokhtar, F., Bertozzi, W., Boeglin, W.U., Botto, T., Brash, E.J., Breuer, H., Brown, E., Burtin, E., Calarco, J.R., Cavata, C., Chang, C.C., Chant, N.S., Chen, J.-P., Coman, M., Crovelli, D., De Leo, R., Dieterich, S., Escoffier, S., Fissum, K.G., Garde, V., Garibaldi, F., Georgakopoulus, S., Gilad, S., Gilman, R., Glashausser, C., Hansen, J.-O., Higinbotham, D.W., Hotta, A., Huber, G.M., Ibrahim, H., Iodice, M., de Jager, C.W., Jiang, X., Klimenko, A., Kozlov, A., Kumbartzki, G., Kuss, M., Lagamba, L., Laveissiere, G., LeRose, J.J., Lindgren, R.A., Liyanage, N., Lolos, G.J., Lourie, R.W., Margaziotis, D.J., Marie, F., Markowitz, P., McAleer, S., Meekins, D., Michaels, R., Milbrath, B.D., Mitchell, J., Nappa, J., Neyret, D., Perdrisat, C.F., Potokar, M., Punjabi, V.A., Pussieux, T., Ransome, R.D., Roos, P.G., Rvachev, M., Saha, A., Sirca, S., Suleiman, R., Strauch, S., Templon, J.A., Todor, L., Ulmer, P.E., Urciuoli, G.M., Weinstein, L.B., Wijesooriya, K., Wojtsekhowski, B., Zheng, X., Zhu, L., Jefferson Laboratory E91011 and Hall A Collaborations, Kelly, J.J., Kelly, J.J., Roche, R.E., Chai, Z., Jones, M.K., Gayou, O., Sarty, A.J., Frullani, S., Aniol, K., Beise, E.J., Benmokhtar, F., Bertozzi, W., Boeglin, W.U., Botto, T., Brash, E.J., Breuer, H., Brown, E., Burtin, E., Calarco, J.R., Cavata, C., Chang, C.C., Chant, N.S., Chen, J.-P., Coman, M., Crovelli, D., De Leo, R., Dieterich, S., Escoffier, S., Fissum, K.G., Garde, V., Garibaldi, F., Georgakopoulus, S., Gilad, S., Gilman, R., Glashausser, C., Hansen, J.-O., Higinbotham, D.W., Hotta, A., Huber, G.M., Ibrahim, H., Iodice, M., de Jager, C.W., Jiang, X., Klimenko, A., Kozlov, A., Kumbartzki, G., Kuss, M., Lagamba, L., Laveissiere, G., LeRose, J.J., Lindgren, R.A., Liyanage, N., Lolos, G.J., Lourie, R.W., Margaziotis, D.J., Marie, F., Markowitz, P., McAleer, S., Meekins, D., Michaels, R., Milbrath, B.D., Mitchell, J., Nappa, J., Neyret, D., Perdrisat, C.F., Potokar, M., Punjabi, V.A., Pussieux, T., Ransome, R.D., Roos, P.G., Rvachev, M., Saha, A., Sirca, S., Suleiman, R., Strauch, S., Templon, J.A., Todor, L., Ulmer, P.E., Urciuoli, G.M., Weinstein, L.B., Wijesooriya, K., Wojtsekhowski, B., Zheng, X., Zhu, L., and Jefferson Laboratory E91011 and Hall A Collaborations

Abstract

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W=1.23 GeV at Q2=1.0 (GeV/c)2, obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S1+/M1+)=-(6.84±0.15)% and Re (E1+/M1+)=-(2.91±0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ℓπ≤1 truncation.

Published
2005

16. High energy angular distribution measurements of the exclusive deuteron photodisintegration reaction

Author

Schulte, E C, Afanasev, A, Amarian, M, Aniol, K, Becher, S, Benslama, K, Bimbot, L, Bosted, P, Brash, E, Calarco, J, Chai, Z, Chang, C, Chang, T, Chen, J P, Choi, S, Chudakov, E, Churchwell, S, Crovelli, D, Dieterich, S, Dumalski, S, Dutta, D, Epstein, M, Fissum, K, Fox, B, Frullani, S, Gao, H, Gao, J, Garibaldi, F, Gayou, O, Gilman, R, Glamazdin, A, Glashausser, C, Gomez, J, Gorbenko, V, Hansen, J O, Holt, R J, Hovdebo, J, Huber, G M, De Jager, C W, Jiang, X, Jones, C, Jones, M K, Kelly, J, Kinney, E, Kooijman, E, Kumbartzki, G, Kuss, M, LeRose, J, Liang, M, Lindgren, R, Liyanage, N, Malov, S, Margaziotis, D, Markowitz, D, McCormick, K, Meekins, D, Meziani, Z E, Michaels, R, Mitchell, J, Morand, L, Perdrisat, C, Pomatsalyuk, R, Punjabi, V, Radyushkin, A, Ransome, R, Roche, R, Rvachev, M, Saha, A, Sarty, A, Simon, Daniel, Strauch, S, Suleiman, R, Todor, L, Ulmer, P, Urciuoli, G M, Wijesooriya, K, Wojtsekhowski, B, Xiong, F, Xu, W, Schulte, E C, Afanasev, A, Amarian, M, Aniol, K, Becher, S, Benslama, K, Bimbot, L, Bosted, P, Brash, E, Calarco, J, Chai, Z, Chang, C, Chang, T, Chen, J P, Choi, S, Chudakov, E, Churchwell, S, Crovelli, D, Dieterich, S, Dumalski, S, Dutta, D, Epstein, M, Fissum, K, Fox, B, Frullani, S, Gao, H, Gao, J, Garibaldi, F, Gayou, O, Gilman, R, Glamazdin, A, Glashausser, C, Gomez, J, Gorbenko, V, Hansen, J O, Holt, R J, Hovdebo, J, Huber, G M, De Jager, C W, Jiang, X, Jones, C, Jones, M K, Kelly, J, Kinney, E, Kooijman, E, Kumbartzki, G, Kuss, M, LeRose, J, Liang, M, Lindgren, R, Liyanage, N, Malov, S, Margaziotis, D, Markowitz, D, McCormick, K, Meekins, D, Meziani, Z E, Michaels, R, Mitchell, J, Morand, L, Perdrisat, C, Pomatsalyuk, R, Punjabi, V, Radyushkin, A, Ransome, R, Roche, R, Rvachev, M, Saha, A, Sarty, A, Simon, Daniel, Strauch, S, Suleiman, R, Todor, L, Ulmer, P, Urciuoli, G M, Wijesooriya, K, Wojtsekhowski, B, Xiong, F, and Xu, W

Abstract

The first complete measurements of the angular distributions of the two-body deuteron photodisintegration differential cross section at photon energies above 1.6 GeV were performed at the Thomas Jefferson National Accelerator Facility. The results show a persistent forward-backward asymmetry up to Eγ = 2.4 GeV, the highest-energy measured in this experiment. The Hard Rescattering and the Quark-Gluon string models are in fair agreement with the results.

Published
2002
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17. Polarization measurements in high-energy deuteron photodisintegration

Author

Wijesooriya, K, Afanasev, A, Amarian, M, Aniol, K, Becher, S, Benslama, K, Bimbot, L, Bosted, P, Brash, E, Calarco, J, Chai, Z, Chang, C C, Chang, T, Chen, J P, Choi, S, Chudakov, E, Churchwell, S, Crovelli, D, Dieterich, S, Dumalski, S, Dutta, D, Epstein, M, Fissum, K, Fox, B, Frullani, S, Gao, H, Gao, J, Garibaldi, F, Gayou, O, Gilman, R, Glamazdin, S, Glashausser, C, Gomez, J, Gorbenko, V, Hansen, O, Holt, R J, Hovdebo, J, Huber, G M, De Jager, C W, Jiang, X, Jones, C, Jones, M K, Kelly, J, Kinney, E, Kooijman, E, Kumbartzki, G, Kuss, M, LeRose, J, Liang, M, Lindgren, R, Liyanage, N, Malov, S, Margaziotis, D J, Markowitz, P, McCormick, K, Meekins, D, Meziani, Z E, Michaels, R, Mitchell, J, Morand, L, Perdrisat, C F, Pomatsalyuk, R, Punjabi, V, Ransome, R D, Roche, R, Rvachev, M, Saha, A, Sarty, A, Schulte, E C, Simon, Daniel, Strauch, S, Suleiman, R, Todor, L, Ulmer, P E, Urciuoli, G M, Wojtsekhowski, B, Xiong, F, Xu, W, Wijesooriya, K, Afanasev, A, Amarian, M, Aniol, K, Becher, S, Benslama, K, Bimbot, L, Bosted, P, Brash, E, Calarco, J, Chai, Z, Chang, C C, Chang, T, Chen, J P, Choi, S, Chudakov, E, Churchwell, S, Crovelli, D, Dieterich, S, Dumalski, S, Dutta, D, Epstein, M, Fissum, K, Fox, B, Frullani, S, Gao, H, Gao, J, Garibaldi, F, Gayou, O, Gilman, R, Glamazdin, S, Glashausser, C, Gomez, J, Gorbenko, V, Hansen, O, Holt, R J, Hovdebo, J, Huber, G M, De Jager, C W, Jiang, X, Jones, C, Jones, M K, Kelly, J, Kinney, E, Kooijman, E, Kumbartzki, G, Kuss, M, LeRose, J, Liang, M, Lindgren, R, Liyanage, N, Malov, S, Margaziotis, D J, Markowitz, P, McCormick, K, Meekins, D, Meziani, Z E, Michaels, R, Mitchell, J, Morand, L, Perdrisat, C F, Pomatsalyuk, R, Punjabi, V, Ransome, R D, Roche, R, Rvachev, M, Saha, A, Sarty, A, Schulte, E C, Simon, Daniel, Strauch, S, Suleiman, R, Todor, L, Ulmer, P E, Urciuoli, G M, Wojtsekhowski, B, Xiong, F, and Xu, W

Abstract

We present measurements of the recoil proton polarization for the d(γ⃗,p⃗)n reaction at θc.m. = 90° for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization py vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(γ,p)ncross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.

Published
2001
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18. Deeply Virtual Compton Scattering Cross Section at High Bjorken x_{B}.

Author

Georges F, Rashad MNH, Stefanko A, Dlamini M, Karki B, Ali SF, Lin PJ, Ko HS, Israel N, Adikaram D, Ahmed Z, Albataineh H, Aljawrneh B, Allada K, Allison S, Alsalmi S, Androic D, Aniol K, Annand J, Atac H, Averett T, Ayerbe Gayoso C, Bai X, Bane J, Barcus S, Bartlett K, Bellini V, Beminiwattha R, Bericic J, Biswas D, Brash E, Bulumulla D, Campbell J, Camsonne A, Carmignotto M, Castellano J, Chen C, Chen JP, Chetry T, Christy ME, Cisbani E, Clary B, Cohen E, Compton N, Cornejo JC, Covrig Dusa S, Crowe B, Danagoulian S, Danley T, De Persio F, Deconinck W, Defurne M, Desnault C, Di D, Duer M, Duran B, Ent R, Fanelli C, Franklin G, Fuchey E, Gal C, Gaskell D, Gautam T, Glamazdin O, Gnanvo K, Gray VM, Gu C, Hague T, Hamad G, Hamilton D, Hamilton K, Hansen O, Hauenstein F, Henry W, Higinbotham DW, Holmstrom T, Horn T, Huang Y, Huber GM, Hyde CE, Ibrahim H, Jen CM, Jin K, Jones M, Kabir A, Keppel C, Khachatryan V, King PM, Li S, Li WB, Liu J, Liu H, Liyanage A, Magee J, Malace S, Mammei J, Markowitz P, McClellan E, Mazouz M, Meddi F, Meekins D, Mesik K, Michaels R, Mkrtchyan A, Montgomery R, Muñoz Camacho C, Myers LS, Nadel-Turonski P, Nazeer SJ, Nelyubin V, Nguyen D, Nuruzzaman N, Nycz M, Obretch OF, Ou L, Palatchi C, Pandey B, Park S, Park K, Peng C, Pomatsalyuk R, Pooser E, Puckett AJR, Punjabi V, Quinn B, Rahman S, Reimer PE, Roche J, Sapkota I, Sarty A, Sawatzky B, Saylor NH, Schmookler B, Shabestari MH, Shahinyan A, Sirca S, Smith GR, Sooriyaarachchilage S, Sparveris N, Spies R, Su T, Subedi A, Sulkosky V, Sun A, Thorne L, Tian Y, Ton N, Tortorici F, Trotta R, Urciuoli GM, Voutier E, Waidyawansa B, Wang Y, Wojtsekhowski B, Wood S, Yan X, Ye L, Ye Z, Yero C, Zhang J, Zhao Y, and Zhu P

Abstract

We report high-precision measurements of the deeply virtual Compton scattering (DVCS) cross section at high values of the Bjorken variable x_{B}. DVCS is sensitive to the generalized parton distributions of the nucleon, which provide a three-dimensional description of its internal constituents. Using the exact analytic expression of the DVCS cross section for all possible polarization states of the initial and final electron and nucleon, and final state photon, we present the first experimental extraction of all four helicity-conserving Compton form factors (CFFs) of the nucleon as a function of x_{B}, while systematically including helicity flip amplitudes. In particular, the high accuracy of the present data demonstrates sensitivity to some very poorly known CFFs.

Published
2022
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19. Form Factors and Two-Photon Exchange in High-Energy Elastic Electron-Proton Scattering.

Author

Christy ME, Gautam T, Ou L, Schmookler B, Wang Y, Adikaram D, Ahmed Z, Albataineh H, Ali SF, Aljawrneh B, Allada K, Allison SL, Alsalmi S, Androic D, Aniol K, Annand J, Arrington J, Atac H, Averett T, Ayerbe Gayoso C, Bai X, Bane J, Barcus S, Bartlett K, Bellini V, Beminiwattha R, Bericic J, Bhatt H, Bhetuwal D, Biswas D, Brash E, Bulumulla D, Camacho CM, Campbell J, Camsonne A, Carmignotto M, Castellanos J, Chen C, Chen JP, Chetry T, Cisbani E, Clary B, Cohen E, Compton N, Cornejo JC, Covrig Dusa S, Crowe B, Danagoulian S, Danley T, Deconinck W, Defurne M, Desnault C, Di D, Dlamini M, Duer M, Duran B, Ent R, Fanelli C, Fuchey E, Gal C, Gaskell D, Georges F, Gilad S, Glamazdin O, Gnanvo K, Gramolin AV, Gray VM, Gu C, Habarakada A, Hague T, Hamad G, Hamilton D, Hamilton K, Hansen O, Hauenstein F, Hernandez AV, Henry W, Higinbotham DW, Holmstrom T, Horn T, Huang Y, Huber GM, Hyde C, Ibrahim H, Israel N, Jen CM, Jin K, Jones M, Kabir A, Karki B, Keppel C, Khachatryan V, King PM, Li S, Li W, Liu H, Liu J, Liyanage AH, Mack D, Magee J, Malace S, Mammei J, Markowitz P, Mayilyan S, McClellan E, Meddi F, Meekins D, Mesick K, Michaels R, Mkrtchyan A, Moffit B, Montgomery R, Myers LS, Nadel-Turonski P, Nazeer SJ, Nelyubin V, Nguyen D, Nuruzzaman N, Nycz M, Obrecht RF, Ohanyan K, Palatchi C, Pandey B, Park K, Park S, Peng C, Persio FD, Pomatsalyuk R, Pooser E, Puckett AJR, Punjabi V, Quinn B, Rahman S, Rashad MNH, Reimer PE, Riordan S, Roche J, Sapkota I, Sarty A, Sawatzky B, Saylor NH, Shabestari MH, Shahinyan A, Širca S, Smith GR, Sooriyaarachchilage S, Sparveris N, Spies R, Stefanko A, Su T, Subedi A, Sulkosky V, Sun A, Tan Y, Thorne L, Ton N, Tortorici F, Trotta R, Uniyal R, Urciuoli GM, Voutier E, Waidyawansa B, Wojtsekhowski B, Wood S, Yan X, Ye L, Ye ZH, Yero C, Zhang J, Zhao YX, and Zhu P

Abstract

We present new precision measurements of the elastic electron-proton scattering cross section for momentum transfer (Q^{2}) up to 15.75  (GeV/c)^{2}. Combined with existing data, these provide an improved extraction of the proton magnetic form factor at high Q^{2} and double the range over which a longitudinal or transverse separation of the cross section can be performed. The difference between our results and polarization data agrees with that observed at lower Q^{2} and attributed to hard two-photon exchange (TPE) effects, extending to 8  (GeV/c)^{2} the range of Q^{2} for which a discrepancy is established at >95% confidence. We use the discrepancy to quantify the size of TPE contributions needed to explain the cross section at high Q^{2}.

Published
2022
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20. Deep Exclusive Electroproduction of π^{0} at High Q^{2} in the Quark Valence Regime.

Author

Dlamini M, Karki B, Ali SF, Lin PJ, Georges F, Ko HS, Israel N, Rashad MNH, Stefanko A, Adikaram D, Ahmed Z, Albataineh H, Aljawrneh B, Allada K, Allison S, Alsalmi S, Androic D, Aniol K, Annand J, Atac H, Averett T, Ayerbe Gayoso C, Bai X, Bane J, Barcus S, Bartlett K, Bellini V, Beminiwattha R, Bericic J, Biswas D, Brash E, Bulumulla D, Campbell J, Camsonne A, Carmignotto M, Castellano J, Chen C, Chen JP, Chetry T, Christy ME, Cisbani E, Clary B, Cohen E, Compton N, Cornejo JC, Covrig Dusa S, Crowe B, Danagoulian S, Danley T, De Persio F, Deconinck W, Defurne M, Desnault C, Di D, Duer M, Duran B, Ent R, Fanelli C, Franklin G, Fuchey E, Gal C, Gaskell D, Gautam T, Glamazdin O, Gnanvo K, Gray VM, Gu C, Hague T, Hamad G, Hamilton D, Hamilton K, Hansen O, Hauenstein F, Henry W, Higinbotham DW, Holmstrom T, Horn T, Huang Y, Huber GM, Hyde C, Ibrahim H, Jen CM, Jin K, Jones M, Kabir A, Keppel C, Khachatryan V, King PM, Li S, Li W, Liu J, Liu H, Liyanage A, Magee J, Malace S, Mammei J, Markowitz P, McClellan E, Meddi F, Meekins D, Mesik K, Michaels R, Mkrtchyan A, Montgomery R, Muñoz Camacho C, Myers LS, Nadel-Turonski P, Nazeer SJ, Nelyubin V, Nguyen D, Nuruzzaman N, Nycz M, Obretch OF, Ou L, Palatchi C, Pandey B, Park S, Park K, Peng C, Pomatsalyuk R, Pooser E, Puckett AJR, Punjabi V, Quinn B, Rahman S, Reimer PE, Roche J, Sapkota I, Sarty A, Sawatzky B, Saylor NH, Schmookler B, Shabestari MH, Shahinyan A, Sirca S, Smith GR, Sooriyaarachchilage S, Sparveris N, Spies R, Su T, Subedi A, Sulkosky V, Sun A, Thorne L, Tian Y, Ton N, Tortorici F, Trotta R, Urciuoli GM, Voutier E, Waidyawansa B, Wang Y, Wojtsekhowski B, Wood S, Yan X, Ye L, Ye Z, Yero C, Zhang J, Zhao Y, and Zhu P

Abstract

We report measurements of the exclusive neutral pion electroproduction cross section off protons at large values of x_{B} (0.36, 0.48, and 0.60) and Q^{2} (3.1 to 8.4  GeV^{2}) obtained from Jefferson Lab Hall A experiment E12-06-014. The corresponding structure functions dσ_{T}/dt+εdσ_{L}/dt, dσ_{TT}/dt, dσ_{LT}/dt, and dσ_{LT^{'}}/dt are extracted as a function of the proton momentum transfer t-t_{min}. The results suggest the amplitude for transversely polarized virtual photons continues to dominate the cross section throughout this kinematic range. The data are well described by calculations based on transversity generalized parton distributions coupled to a helicity flip distribution amplitude of the pion, thus providing a unique way to probe the structure of the nucleon.

Published
2021
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21. Helicity-Dependent Cross Sections for the Photoproduction of π^{0} Pairs from Nucleons.

Author

Dieterle M, Witthauer L, Fix A, Abt S, Achenbach P, Adlarson P, Afzal F, Aguar Bartolome P, Ahmed Z, Annand JRM, Arends HJ, Bashkanov M, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Dolzhikov AS, Downie EJ, Drexler P, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Günther M, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Käser A, Kashevarov VL, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, Lutterer S, MacGregor IJD, Manley DM, Martel PP, Metag V, Meyer W, Middleton DG, Miskimen R, Mornacchi E, Mullen C, Mushkarenkov A, Neganov A, Neiser A, Oberle M, Ostrick M, Otte PB, Paudyal D, Pedroni P, Polonski A, Powell A, Prakhov SN, Reicherz G, Ron G, Rostomyan T, Sarty A, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strakovsky II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Unverzagt M, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Wolfes M, and Zana LA

Abstract

The double-polarization observable E and helicity-dependent cross sections σ_{1/2}, σ_{3/2} have been measured for the photoproduction of π^{0} pairs off quasifree protons and neutrons at the Mainz MAMI accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost 4π covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the γN→Nπ^{0}π^{0} reaction. They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. The comparison of the prediction and the refit demonstrates the large impact of the new data.

Published
2020
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22. Signatures of the d^{*}(2380) Hexaquark in d(γ,pn[over →]).

Author

Bashkanov M, Watts DP, Kay SJD, Abt S, Achenbach P, Adlarson P, Afzal F, Ahmed Z, Akondi CS, Annand JRM, Arends HJ, Beck R, Biroth M, Borisov N, Braghieri A, Briscoe WJ, Cividini F, Collicott C, Costanza S, Denig A, Downie EJ, Drexler P, Fegan S, Fix A, Gardner S, Ghosal D, Glazier DI, Gorodnov I, Gradl W, Günther M, Gurevich D, Heijkenskjöld L, Hornidge D, Huber GM, Käser A, Kashevarov VL, Korolija M, Krusche B, Lazarev A, Livingston K, Lutterer S, MacGregor IJD, Manley DM, Martel PP, Miskimen R, Mornacchi E, Mullen C, Neganov A, Neiser A, Ostrick M, Otte PB, Paudyal D, Pedroni P, Powell A, Prakhov SN, Ron G, Sarty A, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strakovsky II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Usov YA, Wagner S, Walford NK, Werthmüller D, Wettig J, Wolfes M, Zachariou N, and Zana LA

Abstract

We report a measurement of the spin polarization of the recoiling neutron in deuterium photodisintegration, utilizing a new large acceptance polarimeter within the Crystal Ball at MAMI. The measured photon energy range of 300-700 MeV provides the first measurement of recoil neutron polarization at photon energies where the quark substructure of the deuteron plays a role, thereby providing important new constraints on photodisintegration mechanisms. A very high neutron polarization in a narrow structure centered around E_{γ}∼570  MeV is observed, which is inconsistent with current theoretical predictions employing nucleon resonance degrees of freedom. A Legendre polynomial decomposition suggests this behavior could be related to the excitation of the d^{*}(2380) hexaquark.

Published
2020
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23. Unique Access to u-Channel Physics: Exclusive Backward-Angle Omega Meson Electroproduction.

Author

Li WB, Huber GM, Blok HP, Gaskell D, Horn T, Semenov-Tian-Shansky K, Pire B, Szymanowski L, Laget JM, Aniol K, Arrington J, Beise EJ, Boeglin W, Brash EJ, Breuer H, Chang CC, Christy ME, Ent R, Gibson EF, Holt RJ, Jin S, Jones MK, Keppel CE, Kim W, King PM, Kovaltchouk V, Liu J, Lolos GJ, Mack DJ, Margaziotis DJ, Markowitz P, Matsumura A, Meekins D, Miyoshi T, Mkrtchyan H, Niculescu I, Okayasu Y, Pentchev L, Perdrisat C, Potterveld D, Punjabi V, Reimer PE, Reinhold J, Roche J, Roos PG, Sarty A, Smith GR, Tadevosyan V, Tang LG, Tvaskis V, Volmer J, Vulcan W, Warren G, Wood SA, Xu C, and Zheng X

Abstract

Backward-angle meson electroproduction above the resonance region, which was previously ignored, is anticipated to offer unique access to the three quark plus sea component of the nucleon wave function. In this Letter, we present the first complete separation of the four electromagnetic structure functions above the resonance region in exclusive ω electroproduction off the proton, ep→e^{'}pω, at central Q^{2} values of 1.60, 2.45  GeV^{2}, at W=2.21  GeV. The results of our pioneering -u≈-u_{min} study demonstrate the existence of a unanticipated backward-angle cross section peak and the feasibility of full L/T/LT/TT separations in this never explored kinematic territory. At Q^{2}=2.45  GeV^{2}, the observed dominance of σ_{T} over σ_{L}, is qualitatively consistent with the collinear QCD description in the near-backward regime, in which the scattering amplitude factorizes into a hard subprocess amplitude and baryon to meson transition distribution amplitudes: universal nonperturbative objects only accessible through backward-angle kinematics.

Published
2019
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24. Study of η and η' Photoproduction at MAMI.

Author

Kashevarov VL, Ott P, Prakhov S, Adlarson P, Afzal F, Ahmed Z, Akondi CS, Annand JRM, Arends HJ, Beck R, Braghieri A, Briscoe WJ, Cividini F, Codling R, Collicott C, Costanza S, Denig A, Downie EJ, Dieterle M, Ferretti Bondy MI, Fil'kov LV, Fix A, Gardner S, Garni S, Glazier DI, Glowa D, Gradl W, Gurevich G, Hamilton DJ, Hornidge D, Howdle D, Huber GM, Käser A, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Linturi J, Lisin V, Livingston K, MacGregor IJD, MacRae R, Mancell J, Manley DM, Martel PP, McGeorge JC, McNicol E, Middleton DG, Miskimen R, Mornacchi E, Mullen C, Mushkarenkov A, Neiser A, Oberle M, Ostrick M, Otte PB, Oussena B, Paudyal D, Pedroni P, Polyanski VV, Rajabi A, Reicherz G, Robinson J, Rosner G, Rostomyan T, Sarty A, Schott DM, Schumann S, Sfienti C, Sokhoyan V, Spieker K, Steffen O, Strandberg B, Strakovsky II, Strub T, Supek I, Taragin MF, Thiel A, Thiel M, Tiator L, Thomas A, Unverzagt M, Wagner S, Watts DP, Werthmüller D, Wettig J, Witthauer L, Wolfes M, Workman RL, and Zana L

Abstract

The reactions γp→ηp and γp→η^{'}p are measured from their thresholds up to the center-of-mass energy W=1.96  GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η^{'} threshold, W=1896  MeV (E_{γ}=1447  MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η^{'} total cross section from its threshold, can only be explained by a strong coupling of the poorly known N(1895)1/2^{-} state to both ηp and η^{'}p. Including the new high-accuracy results in the ηMAID fit to available η and η^{'} photoproduction data allows the determination of the N(1895)1/2^{-} properties.

Published
2017
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25. Insight into the Narrow Structure in η Photoproduction on the Neutron from Helicity-Dependent Cross Sections.

Author

Witthauer L, Dieterle M, Abt S, Achenbach P, Afzal F, Ahmed Z, Annand JR, Arends HJ, Bashkanov M, Beck R, Biroth M, Borisov NS, Braghieri A, Briscoe WJ, Cividini F, Costanza S, Collicott C, Denig A, Downie EJ, Drexler P, Ferretti-Bondy MI, Gardner S, Garni S, Glazier DI, Glowa D, Gradl W, Günther M, Gurevich GM, Hamilton D, Hornidge D, Huber GM, Käser A, Kashevarov VL, Kay S, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev AB, Linturi JM, Lisin V, Livingston K, Lutterer S, MacGregor IJ, Mancell J, Manley DM, Martel PP, Metag V, Meyer W, Miskimen R, Mornacchi E, Mushkarenkov A, Neganov AB, Neiser A, Oberle M, Ostrick M, Otte PB, Paudyal D, Pedroni P, Polonski A, Prakhov SN, Rajabi A, Reicherz G, Ron G, Rostomyan T, Sarty A, Sfienti C, Sikora MH, Sokhoyan V, Spieker K, Steffen O, Strakovski II, Strub T, Supek I, Thiel A, Thiel M, Thomas A, Unverzagt M, Usov YA, Wagner S, Walford NK, Watts DP, Werthmüller D, Wettig J, Wolfes M, and Zana L

Abstract

The double polarization observable E and the helicity dependent cross sections σ_{1/2} and σ_{3/2} were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π^{0}. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ_{1/2} and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N 1/2^{-} (S_{11}) and N 1/2^{+} (P_{11}). Furthermore, the extracted Legendre coefficients of the angular distributions for σ_{1/2} are in good agreement with recent reaction model predictions assuming a narrow resonance in the P_{11} wave as the origin of this structure.

Published
2016
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26. Measurements of double-polarized compton scattering asymmetries and extraction of the proton spin polarizabilities.

Author

Martel PP, Miskimen R, Aguar-Bartolome P, Ahrens J, Akondi CS, Annand JR, Arends HJ, Barnes W, Beck R, Bernstein A, Borisov N, Braghieri A, Briscoe WJ, Cherepnya S, Collicott C, Costanza S, Denig A, Dieterle M, Downie EJ, Fil'kov LV, Garni S, Glazier DI, Gradl W, Gurevich G, Hall Barrientos P, Hamilton D, Hornidge D, Howdle D, Huber GM, Jude TC, Kaeser A, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, MacGregor IJ, Mancell J, Manley DM, Meyer W, Middleton DG, Mushkarenkov A, Nefkens BM, Neganov A, Nikolaev A, Oberle M, Ortega Spina H, Ostrick M, Ott P, Otte PB, Oussena B, Pedroni P, Polonski A, Polyansky V, Prakhov S, Rajabi A, Reicherz G, Rostomyan T, Sarty A, Schrauf S, Schumann S, Sikora MH, Starostin A, Steffen O, Strakovsky II, Strub T, Supek I, Thiel M, Tiator L, Thomas A, Unverzagt M, Usov Y, Watts DP, Witthauer L, Werthmüller D, and Wolfes M

Abstract

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4)  fm(4).

Published
2015
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27. Measurement of the transverse target and beam-target asymmetries in η meson photoproduction at MAMI.

Author

Akondi CS, Annand JR, Arends HJ, Beck R, Bernstein A, Borisov N, Braghieri A, Briscoe WJ, Cherepnya S, Collicott C, Costanza S, Downie EJ, Dieterle M, Fix A, Fil'kov LV, Garni S, Glazier DI, Gradl W, Gurevich G, Hall Barrientos P, Hamilton D, Hornidge D, Howdle D, Huber GM, Kashevarov VL, Keshelashvili I, Kondratiev R, Korolija M, Krusche B, Lazarev A, Lisin V, Livingston K, MacGregor IJ, Mancel J, Manley DM, Martel P, McNicoll EF, Meyer W, Middleton D, Miskimen R, Mushkarenkov A, Nefkens BM, Neganov A, Nikolaev A, Oberle M, Ostrick M, Ortega H, Ott P, Otte PB, Oussena B, Pedroni P, Polonski A, Polyanski VV, Prakhov S, Reicherz G, Rostomyan T, Sarty A, Schumann S, Steffen O, Strakovsky II, Strub T, Supek I, Tiator L, Thomas A, Unverzagt M, Usov YA, Watts DP, Werthmüller D, Witthauer L, and Wolfes M

Abstract

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the γ[over →]p[over →]→ηp reaction up to a center-of-mass energy of W=1.9  GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. All existing model predictions fail to reproduce the new data indicating a significant impact on our understanding of the underlying dynamics of η meson photoproduction. The peculiar nodal structure observed in existing T data close to threshold is not confirmed.

Published
2014
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28. Separated response function ratios in exclusive, forward π(±) electroproduction.

Author

Huber GM, Blok HP, Butuceanu C, Gaskell D, Horn T, Mack DJ, Abbott D, Aniol K, Anklin H, Armstrong C, Arrington J, Assamagan K, Avery S, Baker OK, Barrett B, Beise EJ, Bochna C, Boeglin W, Brash EJ, Breuer H, Chang CC, Chant N, Christy ME, Dunne J, Eden T, Ent R, Fenker H, Gibson EF, Gilman R, Gustafsson K, Hinton W, Holt RJ, Jackson H, Jin S, Jones MK, Keppel CE, Kim PH, Kim W, King PM, Klein A, Koltenuk D, Kovaltchouk V, Liang M, Liu J, Lolos GJ, Lung A, Margaziotis DJ, Markowitz P, Matsumura A, McKee D, Meekins D, Mitchell J, Miyoshi T, Mkrtchyan H, Mueller B, Niculescu G, Niculescu I, Okayasu Y, Pentchev L, Perdrisat C, Pitz D, Potterveld D, Punjabi V, Qin LM, Reimer PE, Reinhold J, Roche J, Roos PG, Sarty A, Shin IK, Smith GR, Stepanyan S, Tang LG, Tadevosyan V, Tvaskis V, van der Meer RL, Vansyoc K, Van Westrum D, Vidakovic S, Volmer J, Vulcan W, Warren G, Wood SA, Xu C, Yan C, Zhao WX, Zheng X, and Zihlmann B

Abstract

The study of exclusive π(±) electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio RL=σL(π-)/σL(π+) is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of RT=σT(π-)/σT(π+) from unity at small -t, to 1/4 at large -t, would suggest a transition from coupling to a (virtual) pion to coupling to individual quarks. Furthermore, the mentioned ratios may show an earlier approach to perturbative QCD than the individual cross sections. We have performed the first complete separation of the four unpolarized electromagnetic structure functions above the dominant resonances in forward, exclusive π(±) electroproduction on the deuteron at central Q(2) values of 0.6, 1.0, 1.6  GeV(2) at W=1.95  GeV, and Q(2)=2.45  GeV(2) at W=2.22  GeV. Here, we present the L and T cross sections, with emphasis on RL and RT, and compare them with theoretical calculations. Results for the separated ratio RL indicate dominance of the pion-pole diagram at low -t, while results for RT are consistent with a transition between pion knockout and quark knockout mechanisms.

Published
2014
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29. Hard two-body photodisintegration of 3He.

Author

Pomerantz I, Ilieva Y, Gilman R, Higinbotham DW, Piasetzky E, Strauch S, Adhikari KP, Aghasyan M, Allada K, Amaryan MJ, Anefalos Pereira S, Anghinolfi M, Baghdasaryan H, Ball J, Baltzell NA, Battaglieri M, Batourine V, Beck A, Beck S, Bedlinskiy I, Berman BL, Biselli AS, Boeglin W, Bono J, Bookwalter C, Boiarinov S, Briscoe WJ, Brooks WK, Bubis N, Burkert V, Camsonne A, Canan M, Carman DS, Celentano A, Chandavar S, Charles G, Chirapatpimol K, Cisbani E, Cole PL, Contalbrigo M, Crede V, Cusanno F, D'Angelo A, Daniel A, Dashyan N, de Jager CW, De Vita R, De Sanctis E, Deur A, Djalali C, Dodge GE, Doughty D, Dupre R, Dutta C, Egiyan H, El Alaoui A, El Fassi L, Eugenio P, Fedotov G, Fegan S, Fleming JA, Fradi A, Garibaldi F, Geagla O, Gevorgyan N, Giovanetti KL, Girod FX, Glister J, Goetz JT, Gohn W, Golovatch E, Gothe RW, Griffioen KA, Guegan B, Guidal M, Guo L, Hafidi K, Hakobyan H, Harrison N, Heddle D, Hicks K, Ho D, Holtrop M, Hyde CE, Ireland DG, Ishkhanov BS, Isupov EL, Jiang X, Jo HS, Joo K, Katramatou AT, Keller D, Khandaker M, Khetarpal P, Khrosinkova E, Kim A, Kim W, Klein FJ, Koirala S, Kubarovsky A, Kubarovsky V, Kuleshov SV, Kvaltine ND, Lee B, LeRose JJ, Lewis S, Lindgren R, Livingston K, Lu HY, MacGregor IJ, Mao Y, Martinez D, Mayer M, McCullough E, McKinnon B, Meekins D, Meyer CA, Michaels R, Mineeva T, Mirazita M, Moffit B, Mokeev V, Montgomery RA, Moutarde H, Munevar E, Munoz Camacho C, Nadel-Turonski P, Nasseripour R, Nepali CS, Niccolai S, Niculescu G, Niculescu I, Osipenko M, Ostrovidov AI, Pappalardo LL, Paremuzyan R, Park K, Park S, Petratos GG, Phelps E, Pisano S, Pogorelko O, Pozdniakov S, Procureur S, Protopopescu D, Puckett AJ, Qian X, Qiang Y, Ricco G, Rimal D, Ripani M, Ritchie BG, Rodriguez I, Ron G, Rosner G, Rossi P, Sabatié F, Saha A, Saini MS, Sarty AJ, Sawatzky B, Saylor NA, Schott D, Schulte E, Schumacher RA, Seder E, Seraydaryan H, Shneor R, Smith GD, Sokhan D, Sparveris N, Stepanyan SS, Stepanyan S, Stoler P, Subedi R, Sulkosky V, Taiuti M, Tang W, Taylor CE, Tkachenko S, Ungaro M, Vernarsky B, Vineyard MF, Voskanyan H, Voutier E, Walford NK, Wang Y, Watts DP, Weinstein LB, Weygand DP, Wojtsekhowski B, Wood MH, Yan X, Yao H, Zachariou N, Zhan X, Zhang J, Zhao ZW, Zheng X, and Zonta I

Abstract

We have measured cross sections for the γ(3)He → pd reaction at photon energies of 0.4-1.4 GeV and a center-of-mass angle of 90°. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron.

Published
2013
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30. Precise extraction of the induced polarization in the 4He(e,e'p)3H reaction.

Author

Malace SP, Paolone M, Strauch S, Albayrak I, Arrington J, Berman BL, Brash EJ, Briscoe B, Camsonne A, Chen JP, Christy ME, Chudakov E, Cisbani E, Craver B, Cusanno F, Ent R, Garibaldi F, Gilman R, Glamazdin O, Glister J, Higinbotham DW, Hyde-Wright CE, Ilieva Y, de Jager CW, Jiang X, Jones MK, Keppel CE, Khrosinkova E, Kuchina E, Kumbartzki G, Lee B, Lindgren R, Margaziotis DJ, Meekins D, Michaels R, Park K, Pentchev L, Perdrisat CF, Piasetzky E, Punjabi VA, Puckett AJ, Qian X, Qiang Y, Ransome RD, Saha A, Sarty AJ, Schulte E, Solvignon P, Subedi RR, Tang L, Tedeschi D, Tvaskis V, Udias JM, Ulmer PE, Vignote JR, Wesselmann FR, Wojtsekhowski B, and Zhan X

Abstract

We measured with unprecedented precision the induced polarization P(y) in (4)He(e,e'p)(3)H at Q(2)=0.8 and 1.3  (GeV/c)(2). The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent charge-exchange term in the latter calculation.

Published
2011
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31. Polarization transfer in the 4He(e,e'p)3H reaction at Q2=0.8 and 1.3 (GeV/c)2.

Author

Paolone M, Malace SP, Strauch S, Albayrak I, Arrington J, Berman BL, Brash EJ, Briscoe B, Camsonne A, Chen JP, Christy ME, Chudakov E, Cisbani E, Craver B, Cusanno F, Ent R, Garibaldi F, Gilman R, Glamazdin O, Glister J, Higinbotham DW, Hyde-Wright CE, Ilieva Y, de Jager CW, Jiang X, Jones MK, Keppel CE, Khrosinkova E, Kuchina E, Kumbartzki G, Lee B, Lindgren R, Margaziotis DJ, Meekins D, Michaels R, Park K, Pentchev L, Perdrisat CF, Piasetzky E, Punjabi VA, Puckett AJ, Qian X, Qiang Y, Ransome RD, Saha A, Sarty AJ, Schulte E, Solvignon P, Subedi RR, Tang L, Tedeschi D, Tvaskis V, Udias JM, Ulmer PE, Vignote JR, Wesselmann FR, Wojtsekhowski B, and Zhan X

Abstract

Proton recoil polarization was measured in the quasielastic 4He(e,e'p)3H reaction at Q{2}=0.8 and 1.3  (GeV/c){2} with unprecedented precision. The polarization-transfer coefficients are found to differ from those of the 1H(e,e'p) reaction, contradicting a relativistic distorted-wave approximation and favoring either the inclusion of medium-modified proton form factors predicted by the quark-meson coupling model or a spin-dependent charge-exchange final-state interaction. For the first time, the polarization-transfer ratio is studied as a function of the virtuality of the proton.

Published
2010
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32. High-resolution spectroscopy of Lambda16N by electroproduction.

Author

Cusanno F, Urciuoli GM, Acha A, Ambrozewicz P, Aniol KA, Baturin P, Bertin PY, Benaoum H, Blomqvist KI, Boeglin WU, Breuer H, Brindza P, Bydzovský P, Camsonne A, Chang CC, Chen JP, Choi S, Chudakov EA, Cisbani E, Colilli S, Coman L, Craver BJ, De Cataldo G, de Jager CW, De Leo R, Deur AP, Ferdi C, Feuerbach RJ, Folts E, Fratoni R, Frullani S, Garibaldi F, Gayou O, Giuliani F, Gomez J, Gricia M, Hansen JO, Hayes D, Higinbotham DW, Holmstrom TK, Hyde CE, Ibrahim HF, Iodice M, Jiang X, Kaufman LJ, Kino K, Kross B, Lagamba L, LeRose JJ, Lindgren RA, Lucentini M, Margaziotis DJ, Markowitz P, Marrone S, Meziani ZE, McCormick K, Michaels RW, Millener DJ, Miyoshi T, Moffit B, Monaghan PA, Moteabbed M, Muñoz Camacho C, Nanda S, Nappi E, Nelyubin VV, Norum BE, Okasyasu Y, Paschke KD, Perdrisat CF, Piasetzky E, Punjabi VA, Qiang Y, Raue B, Reimer PE, Reinhold J, Reitz B, Roche RE, Rodriguez VM, Saha A, Santavenere F, Sarty AJ, Segal J, Shahinyan A, Singh J, Sirca S, Snyder R, Solvignon PH, Sotona M, Subedi R, Sulkosky VA, Suzuki T, Ueno H, Ulmer PE, Veneroni P, Voutier E, Wojtsekhowski BB, Zheng X, and Zorn C

Abstract

An experimental study of the (16)O(e,e'K(+))(Lambda)(16)N reaction has been performed at Jefferson Lab. A thin film of falling water was used as a target. This permitted a simultaneous measurement of the p(e,e'K(+))Lambda, Sigma(0) exclusive reactions and a precise calibration of the energy scale. A ground-state binding energy of 13.76+/-0.16 MeV was obtained for (Lambda)(16)N with better precision than previous measurements on the mirror hypernucleus (Lambda)(16)O. Precise energies have been determined for peaks arising from a Lambda in s and p orbits coupled to the p(1/2) and p(3/2) hole states of the (15)N core nucleus.

Published
2009
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33. Measurements of the proton elastic-form-factor ratio mu pG p E/G p M at low momentum transfer.

Author

Ron G, Glister J, Lee B, Allada K, Armstrong W, Arrington J, Beck A, Benmokhtar F, Berman BL, Boeglin W, Brash E, Camsonne A, Calarco J, Chen JP, Choi S, Chudakov E, Coman L, Craver B, Cusanno F, Dumas J, Dutta C, Feuerbach R, Freyberger A, Frullani S, Garibaldi F, Gilman R, Hansen O, Higinbotham DW, Holmstrom T, Hyde CE, Ibrahim H, Ilieva Y, de Jager CW, Jiang X, Jones MK, Kang H, Kelleher A, Khrosinkova E, Kuchina E, Kumbartzki G, LeRose JJ, Lindgren R, Markowitz P, May-Tal Beck S, McCullough E, Meekins D, Meziane M, Meziani ZE, Michaels R, Moffit B, Norum BE, Oh Y, Olson M, Paolone M, Paschke K, Perdrisat CF, Piasetzky E, Potokar M, Pomatsalyuk R, Pomerantz I, Puckett A, Punjabi V, Qian X, Qiang Y, Ransome R, Reyhan M, Roche J, Rousseau Y, Saha A, Sarty AJ, Sawatzky B, Schulte E, Shabestari M, Shahinyan A, Shneor R, Sirca S, Slifer K, Solvignon P, Song J, Sparks R, Subedi R, Strauch S, Urciuoli GM, Wang K, Wojtsekhowski B, Yan X, Yao H, Zhan X, and Zhu X

Abstract

High-precision measurements of the proton elastic form-factor ratio, mu pG p E/G p M, have been made at four-momentum transfer, Q2, values between 0.2 and 0.5 GeV2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q2 range the deviation from unity is primarily due to G p E being smaller than expected.

Published
2007
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34. High resolution spectroscopy of (lambda)(12)B by electroproduction.

Author

Iodice M, Cusanno F, Acha A, Ambrozewicz P, Aniol KA, Baturin P, Bertin PY, Benaoum H, Blomqvist KI, Boeglin WU, Breuer H, Brindza P, Bydzovský P, Camsonne A, Chang CC, Chen JP, Choi S, Chudakov EA, Cisbani E, Colilli S, Coman L, Craver BJ, De Cataldo G, de Jager CW, De Leo R, Deur AP, Ferdi C, Feuerbach RJ, Folts E, Fratoni R, Frullani S, Garibaldi F, Gayou O, Giulani F, Gomez J, Gricia M, Hansen JO, Hayes D, Higinbotham DW, Holmstrom TK, Hyde CE, Ibrahim HF, Jiang X, Kaufman LJ, Kino K, Kross B, Lagamba L, LeRose JJ, Lindgren RA, Lucentini M, Margaziotis DJ, Markowitz P, Marrone S, Meziani ZE, McCormick K, Michaels RW, Millener DJ, Miyoshi T, Moffit B, Monaghan PA, Moteabbed M, Muñoz Camacho C, Nanda S, Nappi E, Nelyubin VV, Norum BE, Okasyasu Y, Paschke KD, Perdrisat CF, Piasetzky E, Punjabi VA, Qiang Y, Raue B, Reimer PE, Reinhold J, Reitz B, Roche RE, Rodriguez VM, Saha A, Santavenere F, Sarty AJ, Segal J, Shahinyan A, Singh J, Sirca S, Snyder R, Solvignon PH, Sotona M, Subedi R, Sulkosky VA, Suzuki T, Ueno H, Ulmer PE, Urciuoli GM, Veneroni P, Voutier E, Wojtsekhowski BB, Ye Y, Zheng X, Zhou S, and Zorn C

Abstract

An experiment measuring electroproduction of hypernuclei has been performed in hall A at Jefferson Lab on a 12C target. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring imaging Cherenkov detector were added to the hall A standard equipment. An unprecedented energy resolution of less than 700 keV FWHM has been achieved. Thus, the observed (Lambda)(12)B spectrum shows for the first time identifiable strength in the core-excited region between the ground-state s-wave Lambda peak and the 11 MeV p-wave Lambda peak.

Published
2007
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35. Measurements of the generalized electric and magnetic polarizabilities of the proton at low Q2 using the virtual-compton-scattering reaction.

Author

Bourgeois P, Sato Y, Shaw J, Alarcon R, Bernstein AM, Bertozzi W, Botto T, Calarco J, Casagrande F, Distler MO, Dow K, Farkondeh M, Georgakopoulos S, Gilad S, Hicks R, Holtrop M, Hotta A, Jiang X, Karabarbounis A, Kirkpatrick J, Kowalski S, Milner R, Miskimen R, Nakagawa I, Papanicolas CN, Sarty AJ, Sirca S, Six E, Sparveris NF, Stave S, Stiliaris E, Tamae T, Tsentalovich G, Tschalaer C, Turchinetz W, Zhou ZL, and Zwart T

Abstract

The mean square polarizability radii of the proton have been measured for the first time in a virtual-Compton-scattering experiment performed at the MIT-Bates out-of-plane scattering facility. Response functions and polarizabilities obtained from a dispersion analysis of the data at Q2 = 0.057 GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory. The data support the dominance of mesonic effects in the polarizabilities.

Published
2006
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36. Determination of the pion charge form factor at Q2=1.60 and 2.45 (GeV/c)2.

Author

Horn T, Aniol K, Arrington J, Barrett B, Beise EJ, Blok HP, Boeglin W, Brash EJ, Breuer H, Chang CC, Christy ME, Ent R, Gaskell D, Gibson E, Holt RJ, Huber GM, Jin S, Jones MK, Keppel CE, Kim W, King PM, Kovaltchouk V, Liu J, Lolos GJ, Mack DJ, Margaziotis DJ, Markowitz P, Matsumura A, Meekins D, Miyoshi T, Mkrtchyan H, Niculescu I, Okayasu Y, Pentchev L, Perdrisat C, Potterveld D, Punjabi V, Reimer P, Reinhold J, Roche J, Roos PG, Sarty A, Smith GR, Tadevosyan V, Tang LG, Tvaskis V, Vidakovic S, Volmer J, Vulcan W, Warren G, Wood SA, Xu C, and Zheng X

Abstract

The 1H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F(pi)) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F(pi) is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative quantum chromodynamics prediction.

Published
2006
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37. Recoil polarization for delta excitation in pion electroproduction.

Author

Kelly JJ, Roché RE, Chai Z, Jones MK, Gayou O, Sarty AJ, Frullani S, Aniol K, Beise EJ, Benmokhtar F, Bertozzi W, Boeglin WU, Botto T, Brash EJ, Breuer H, Brown E, Burtin E, Calarco JR, Cavata C, Chang CC, Chant NS, Chen JP, Coman M, Crovelli D, De Leo R, Dieterich S, Escoffier S, Fissum KG, Garde V, Garibaldi F, Georgakopoulus S, Gilad S, Gilman R, Glashausser C, Hansen JO, Higinbotham DW, Hotta A, Huber GM, Ibrahim H, Iodice M, de Jager CW, Jiang X, Klimenko A, Kozlov A, Kumbartzki G, Kuss M, Lagamba L, Laveissière G, Lerose JJ, Lindgren RA, Liyanage N, Lolos GJ, Lourie RW, Margaziotis DJ, Marie F, Markowitz P, McAleer S, Meekins D, Michaels R, Milbrath BD, Mitchell J, Nappa J, Neyret D, Perdrisat CF, Potokar M, Punjabi VA, Pussieux T, Ransome RD, Roos PG, Rvachev M, Saha A, Sirca S, Suleiman R, Strauch S, Templon JA, Todor L, Ulmer PE, Urciuoli GM, Weinstein LB, Wijesooriya K, Wojtsekhowski B, Zheng X, and Zhu L

Abstract

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation.

Published
2005
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38. Precision Rosenbluth measurement of the proton elastic form factors.

Author

Qattan IA, Arrington J, Segel RE, Zheng X, Aniol K, Baker OK, Beams R, Brash EJ, Calarco J, Camsonne A, Chen JP, Christy ME, Dutta D, Ent R, Frullani S, Gaskell D, Gayou O, Gilman R, Glashausser C, Hafidi K, Hansen JO, Higinbotham DW, Hinton W, Holt RJ, Huber GM, Ibrahim H, Jisonna L, Jones MK, Keppel CE, Kinney E, Kumbartzki GJ, Lung A, Margaziotis DJ, McCormick K, Meekins D, Michaels R, Monaghan P, Moussiegt P, Pentchev L, Perdrisat C, Punjabi V, Ransome R, Reinhold J, Reitz B, Saha A, Sarty A, Schulte EC, Slifer K, Solvignon P, Sulkosky V, Wijesooriya K, and Zeidman B

Abstract

We report the results of a new Rosenbluth measurement of the proton electromagnetic form factors at Q2 values of 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting the recoiling proton, in contrast to previous measurements which detected the scattered electron. Cross sections were determined to 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was determined to 4%-8% and showed mu(p)G(E)/G(M) approximately 1. These results are consistent with, and much more precise than, previous Rosenbluth extractions. They are inconsistent with recent polarization transfer measurements of similar precision, implying a systematic difference between the techniques.

Published
2005
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39. Investigation of the conjectured nucleon deformation at low momentum transfer.

Author

Sparveris NF, Alarcon R, Bernstein AM, Bertozzi W, Botto T, Bourgeois P, Calarco J, Casagrande F, Distler MO, Dow K, Farkondeh M, Georgakopoulos S, Gilad S, Hicks R, Holtrop M, Hotta A, Jiang X, Karabarbounis A, Kirkpatrick J, Kowalski S, Milner R, Miskimen R, Nakagawa I, Papanicolas CN, Sarty AJ, Sato Y, Sirca S, Shaw J, Six E, Stave S, Stiliaris E, Tamae T, Tsentalovich G, Tschalaer C, Turchinetz W, Zhou ZL, and Zwart T

Abstract

We report new precise H(e,e(')p)pi(0) measurements at the Delta(1232) resonance at Q(2)=0.127 (GeV/c)(2) obtained at the MIT-Bates out-of-plane scattering facility which are particularly sensitive to the transverse electric amplitude (E2) of the gamma(*)N-->Delta transition. The new data have been analyzed together with those of earlier measurements to yield precise quadrupole to dipole amplitude ratios: Re(E(3/2)(1+)/M(3/2)(1+))=(-2.3+/-0.3(stat+syst)+/-0.6(model))% and Re(S(3/2)(1+)/M(3/2)(1+))=(-6.1+/-0.2(stat+syst)+/-0.5(model))% for M(3/2)(1+)=(41.4+/-0.3(stat+syst)+/-0.4(model))(10(-3)/m(pi(+))). The derived amplitudes give credence to the conjecture of deformation in hadrons favoring, at low Q2, the dominance of mesonic effects.

Published
2005
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40. Measurement of the exclusive 3He(e,e'p) reaction below the quasielastic peak.

Author

Kozlov A, Sarty AJ, Aniol KA, Bartsch P, Baumann D, Bertozzi W, Bohinc K, Böhm R, Chen JP, Dale D, Dennis L, Derber S, Ding M, Distler MO, Dragovitsch P, Ewald I, Fissum KG, Friedrich J, Friedrich JM, Geiges R, Gilad S, Jennewein P, Kahrau M, Kohl M, Krygier KW, Liesenfeld A, Margaziotis DJ, Merkel H, Merle P, Müller U, Neuhausen R, Pospischil T, Potokar M, Riccardi G, Roché R, Rosner G, Rowntree D, Schmieden H, Sirca S, Templon JA, Thompson MN, Wagner A, Walcher T, Weis M, Zhao J, Zhou ZL, Golak J, Glöckle W, and Witała H

Abstract

New, high-precision measurements of the 3He(e,e(')p) reaction using the A1 Collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in antiparallel kinematics at energy transfers below the quasielastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable differences in the cross-section behavior from theoretical predictions based on the plane wave impulse approximation were observed in both the two- and three-body breakup channels. Full Faddeev-type calculations account for some of the observed excess cross-section, but significant differences remain.

Published
2004
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41. Measurement of the generalized polarizabilities of the proton in virtual Compton scattering at Q2=0.92 and 1.76 GeV2.

Author

Laveissière G, Todor L, Degrande N, Jaminion S, Jutier C, Di Salvo R, Van Hoorebeke L, Alexa LC, Anderson BD, Aniol KA, Arundell K, Audit G, Auerbach L, Baker FT, Baylac M, Berthot J, Bertin PY, Bertozzi W, Bimbot L, Boeglin WU, Brash EJ, Breton V, Breuer H, Burtin E, Calarco JR, Cardman LS, Cavata C, Chang CC, Chen JP, Chudakov E, Cisbani E, Dale DS, de Jager CW, De Leo R, Deur A, d'Hose N, Dodge GE, Domingo JJ, Elouadrhiri L, Epstein MB, Ewell LA, Finn JM, Fissum KG, Fonvieille H, Fournier G, Frois B, Frullani S, Furget C, Gao H, Gao J, Garibaldi F, Gasparian A, Gilad S, Gilman R, Glamazdin A, Glashausser C, Gomez J, Gorbenko V, Grenier P, Guichon PA, Hansen JO, Holmes R, Holtrop M, Howell C, Huber GM, Hyde-Wright CE, Incerti S, Iodice M, Jardillier J, Jones MK, Kahl W, Kato S, Katramatou AT, Kelly JJ, Kerhoas S, Ketikyan A, Khayat M, Kino K, Kox S, Kramer LH, Kumar KS, Kumbartzki G, Kuss M, Leone A, LeRose JJ, Liang M, Lindgren RA, Liyanage N, Lolos GJ, Lourie RW, Madey R, Maeda K, Malov S, Manley DM, Marchand C, Marchand D, Margaziotis DJ, Markowitz P, Marroncle J, Martino J, McCormick K, McIntyre J, Mehrabyan S, Merchez F, Meziani ZE, Michaels R, Miller GW, Mougey JY, Nanda SK, Neyret D, Offermann EA, Papandreou Z, Pasquini B, Perdrisat CF, Perrino R, Petratos GG, Platchkov S, Pomatsalyuk R, Prout DL, Punjabi VA, Pussieux T, Quémenér G, Ransome RD, Ravel O, Real JS, Renard F, Roblin Y, Rowntree D, Rutledge G, Rutt PM, Saha A, Saito T, Sarty AJ, Serdarevic A, Smith T, Smirnov G, Soldi K, Sorokin P, Souder PA, Suleiman R, Templon JA, Terasawa T, Tieulent R, Tomasi-Gustaffson E, Tsubota H, Ueno H, Ulmer PE, Urciuoli GM, Vanderhaeghen M, Van De Vyver R, Van der Meer RL, Vernin P, Vlahovic B, Voskanyan H, Voutier E, Watson JW, Weinstein LB, Wijesooriya K, Wilson R, Wojtsekhowski BB, Zainea DG, Zhang WM, Zhao J, and Zhou ZL

Abstract

We report a virtual Compton scattering study of the proton at low c.m. energies. We have determined the structure functions P(LL)-P(TT)/epsilon and P(LT), and the electric and magnetic generalized polarizabilities (GPs) alpha(E)(Q2) and beta(M)(Q2) at momentum transfer Q(2)=0.92 and 1.76 GeV2. The electric GP shows a strong falloff with Q2, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from piN intermediate states.

Published
2004
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42. Polarization transfer in the 4He(e-->,e'p-->)3H reaction up to Q2=2.6 (GeV/c)2.

Author

Strauch S, Dieterich S, Aniol KA, Annand JR, Baker OK, Bertozzi W, Boswell M, Brash EJ, Chai Z, Chen JP, Christy ME, Chudakov E, Cochran A, De Leo R, Ent R, Epstein MB, Finn JM, Fissum KG, Forest TA, Frullani S, Garibaldi F, Gasparian A, Gayou O, Gilad S, Gilman R, Glashausser C, Gomez J, Gorbenko V, Gueye PL, Hansen JO, Higinbotham DW, Hu B, Hyde-Wright CE, Ireland DG, Jackson C, de Jager CW, Jiang X, Jones C, Jones MK, Kellie JD, Kelly JJ, Keppel CE, Kumbartzki G, Kuss M, LeRose JJ, Livingston K, Liyanage N, Malov S, Margaziotis DJ, Meekins D, Michaels R, Mitchell JH, Nanda SK, Nappa J, Perdrisat CF, Punjabi VA, Ransome RD, Roché R, Rosner G, Rvachev M, Sabatie F, Saha A, Sarty A, Udias JM, Ulmer PE, Urciuoli GM, van den Brand JF, Vignote JR, Watts DP, Weinstein LB, Wijesooriya K, and Wojtsekhowski B

Abstract

We have measured the proton recoil polarization in the 4He(e-->,e(')p-->)4H reaction at Q(2)=0.5, 1.0, 1.6, and 2.6 (GeV/c)(2). The measured ratio of polarization transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation indicating that the treatment of final-state interactions is under control.

Published
2003
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43. Relativistic effects and two-body currents in (H)((-->)e(')p)n using out-of-plane detection.

Author

Zhou ZL, Chen J, Soong SB, Young A, Jiang X, Alarcon R, Arenhövel H, Bernstein A, Bertozzi W, Comfort J, Dodson G, Dolfini S, Dooley A, Dow K, Farkhondeh M, Gilad S, Hicks R, Hotta A, Joo K, Kaloskamis NI, Karabarbounis A, Kowalski S, Kunz C, Margaziotis DJ, Mertz C, Miller M, Miskimen R, Miura T, Miyase H, Papanicolas CN, Peterson G, Ramirez A, Rowntree D, Sarty AJ, Shaw J, Suda T, Tamae T, Tieger D, Tjon JA, Tschalaer C, Tsentalovich E, Turchinetz W, Vellidis CE, Warren GA, Weinstein LB, Williamson S, Zhao J, and Zwart T

Abstract

Measurements of the (2)H((-->)e,e(')p)n reaction were performed with the out-of-plane magnetic spectrometers (OOPS) at the MIT-Bates Linear Accelerator. The longitudinal-transverse, f(LT) and f(')(LT), and the transverse-transverse, f(TT), interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q2 = 0.15 (GeV/c)(2). In comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions and the importance of two-body meson-exchange currents and isobar configurations. We demonstrate that such effects can be disentangled by extracting these responses using the novel out-of-plane technique.

Published
2001
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44. Measurement of the high energy two-body deuteron photodisintegration differential cross section.

Author

Schulte EC, Ahmidouch A, Armstrong CS, Arrington J, Asaturyan R, Avery S, Baker OK, Beck DH, Blok HP, Bochna CW, Boeglin W, Bosted PY, Bouwhuis M, Breuer H, Brown DS, Bruell A, Cadman RV, Carlini R, Chant NS, Cochran A, Cole L, Danagoulian S, Day DB, Dunne JA, Dutta D, Ent R, Fenker HC, Fox B, Gan L, Gao H, Garrow K, Gaskell D, Gasparian A, Geesaman DF, Gilman R, Glashausser C, Gueye P, Harvey M, Holt RJ, Jackson HE, Jiang X, Keppel CE, Kinney ER, Liang Y, Lorenzon W, Lung AF, Mack DJ, Markowitz PE, Martin J, McIlhany K, McKee D, Meekins DG, Miller MA, Milner RG, Mitchell JH, Mkrtchyan H, Mueller BA, Nathan AM, Niculescu G, Niculescu I, O'Neill TG, Papavassiliou V, Pate SF, Piercey RB, Potterveld DH, Ransome RD, Reinhold J, Rollinde E, Roos P, Saha A, Sarty AJ, Sawafta R, Segbefia E, Shin T, Stepanyan S, Strauch S, Sutter MF, Tadevosyan V, Tang L, Tieulent R, Uzzle A, Vulcan WF, Wood SA, Xiong F, Yuan L, Zeier M, Zihlmann B, and Ziskin V

Abstract

The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.

Published
2001
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45. Dynamics of the 16O(e, e'p) reaction at high missing energies.

Author

Liyanage N, Anderson BD, Aniol KA, Auerbach L, Baker FT, Berthot J, Bertozzi W, Bertin PY, Bimbot L, Boeglin WU, Brash EJ, Breton V, Breuer H, Burtin E, Calarco JR, Cardman L, Cates GD, Cavata C, Chang CC, Chen JP, Cisbani E, Dale DS, De Leo R, Deur A, Diederich B, Djawotho P, Domingo J, Doyle B, Ducret JE, Epstein MB, Ewell LA, Finn JM, Fissum KG, Fonvieille H, Frois B, Frullani S, Gao J, Garibaldi F, Gasparian A, Gilad S, Gilman R, Glamazdin A, Glashausser C, Gomez J, Gorbenko V, Gorringe T, Hersman FW, Holmes R, Holtrop M, d'Hose N, Howell C, Huber GM, Hyde-Wright CE, Iodice M, de Jager CW, Jaminion S, Jones MK, Joo K, Jutier C, Kahl W, Kato S, Kelly JJ, Kerhoas S, Khandaker M, Khayat M, Kino K, Korsch W, Kramer L, Kumar KS, Kumbartzki G, Laveissière G, Leone A, LeRose JJ, Levchuk L, Liang M, Lindgren RA, Lolos GJ, Lourie RW, Madey R, Maeda K, Malov S, Manley DM, Margaziotis DJ, Markowitz P, Martino J, McCarthy JS, McCormick K, McIntyre J, van der Meer RL, Meziani ZE, Michaels R, Mougey J, Nanda S, Neyret D, Offermann EA, Papandreou Z, Perdrisat CF, Perrino R, Petratos GG, Platchkov S, Pomatsalyuk R, Prout DL, Punjabi VA, Pussieux T, Quéméner G, Ransome RD, Ravel O, Roblin Y, Roche R, Rowntree D, Rutledge GA, Rutt PM, Saha A, Saito T, Sarty AJ, Serdarevic-Offermann A, Smith TP, Soldi A, Sorokin P, Souder P, Suleiman R, Templon JA, Terasawa T, Todor L, Tsubota H, Ueno H, Ulmer PE, Urciuoli GM, Vernin P, van Verst S, Vlahovic B, Voskanyan H, Watson JW, Weinstein LB, Wijesooriya K, Wilson R, Wojtsekhowski B, Zainea DG, Zeps V, Zhao J, and Zhou ZL

Abstract

We measured the cross section and response functions for the quasielastic 16O(e,e'p) reaction for missing energies 25< or =E(m)< or =120 MeV at missing momenta P(m)< or =340 MeV/c. For 25

Published
2001
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46. Search for quadrupole strength in the electroexcitation of the delta+(1232).

Author

Mertz C, Vellidis CE, Alarcon R, Barkhuff DH, Bernstein AM, Bertozzi W, Burkert V, Chen J, Comfort JR, Dodson G, Dolfini S, Dow K, Farkhondeh M, Finn JM, Gilad S, Gothe RW, Jiang X, Joo K, Kaloskamis NI, Karabarbounis A, Kelly JJ, Kowalski S, Kunz C, Lourie RW, McIntyre JI, Milbrath BD, Miskimen R, Mitchell JH, Papanicolas CN, Perdrisat CF, Sarty AJ, Shaw J, Soong SB, Tieger D, Tschalaer C, Turchinetz W, Ulmer PE, Van Verst S, Warren GA, Weinstein LB, Williamson S, Woo RJ, and Young A

Abstract

High-precision 1H(e,e'p)pi(0) measurements at Q2 = 0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma*N-->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole ( I = 3/2) amplitude ratios, R(SM) = (-6.5+/-0.2(stat+sys)+/-2.5(mod))% and R(EM) = (-2.1+/-0.2(stat+sys)+/-2.0(mod))%, are dominated by model error. Previous R(SM) and R(EM) results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account.

Published
2001
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47. Polarization measurements in high-energy deuteron photodisintegration.

Author

Wijesooriya K, Afanasev A, Amarian M, Aniol K, Becher S, Benslama K, Bimbot L, Bosted P, Brash E, Calarco J, Chai Z, Chang CC, Chang T, Chen JP, Choi S, Chudakov E, Churchwell S, Crovelli D, Dieterich S, Dumalski S, Dutta D, Epstein M, Fissum K, Fox B, Frullani S, Gao H, Gao J, Garibaldi F, Gayou O, Gilman R, Glamazdin S, Glashausser C, Gomez J, Gorbenko V, Hansen O, Holt RJ, Hovdebo J, Huber GM, de Jager CW, Jiang X, Jones C, Jones MK, Kelly J, Kinney E, Kooijman E, Kumbartzki G, Kuss M, LeRose J, Liang M, Lindgren R, Liyanage N, Malov S, Margaziotis DJ, Markowitz P, McCormick K, Meekins D, Meziani ZE, Michaels R, Mitchell J, Morand L, Perdrisat CF, Pomatsalyuk R, Punjabi V, Ransome RD, Roche R, Rvachev M, Saha A, Sarty A, Schulte EC, Simon D, Strauch S, Suleiman R, Todor L, Ulmer PE, Urciuoli GM, Wojtsekhowski B, Xiong F, and Xu W

Abstract

We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.

Published
2001
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48. The ep -->e'p eta reaction at and above the S11(1535) baryon resonance.

Author

Thompson R, Dytman S, Kim KY, Mueller J, Adams GS, Amaryan MJ, Anciant E, Anghinolfi M, Asavapibhop B, Auger T, Audit G, Avakian H, Barrow S, Battaglieri M, Beard K, Bektasoglu M, Bertozzi W, Bianchi N, Biselli A, Boiarinov S, Bonner BE, Briscoe WJ, Brooks W, Burkert VD, Calarco JR, Capitani G, Carman DS, Carnahan B, Cole PL, Coleman A, Connelly J, Cords D, Corvisiero P, Crabb D, Crannell H, Cummings J, Day D, Degtyarenko PV, Demirchyan RA, Dennis LC, Deppman A, De Sanctis E, De Vita R, Dhuga KS, Djalali C, Dodge GE, Doughty D, Dragovitsch P, Dugger M, Eckhause M, Efremenko YV, Egiyan H, Egiyan KS, Elouadrhiri L, Farhi L, Feuerbach RJ, Ficenec J, Fissum K, Freyberger A, Funsten H, Gai M, Gavrilov VB, Gilfoyle GP, Giovanetti K, Gilad S, Girard P, Griffioen KA, Guidal M, Guillo M, Gyurjyan V, Hancock D, Hardie J, Heddle D, Heisenberg J, Hersman FW, Hicks K, Hicks RS, Holtrop M, Hyde-Wright CE, Ito MM, Jenkins D, Joo K, Kane J, Khandaker M, Kim W, Klein A, Klein FJ, Klusman M, Kossov M, Kuhn SE, Kuang Y, Laget JM, Lawrence D, Leskin GA, Longhi A, Loukachine K, Lucas M, Magahiz R, Major RW, Manak JJ, Marchand C, Matthews SK, McAleer S, McCarthy J, McNabb JW, Mecking BA, Mestayer MD, Meyer CA, Minehart R, Mirazita M, Miskimen R, Muccifora V, Mutchler GS, Napolitano J, Niyazov RA, Ohandjanyan MS, O'Brien JT, Opper A, Patois Y, Peterson GA, Philips S, Pivnyuk N, Pocanic D, Pogorelko O, Polli E, Preedom BM, Price JW, Qin LM, Raue BA, Reolon AR, Riccardi G, Ricco G, Ripani M, Ritchie BG, Ronchetti F, Rossi P, Roudot F, Rowntree D, Rubin PD, Salgado CW, Sanzone M, Sapunenko V, Sarty A, Sargsyan M, Schumacher RA, Shafi A, Sharabian YG, Shaw J, Shuvalov SM, Skabelin A, Smith T, Smith C, Smith ES, Sober DI, Spraker M, Stepanyan S, Stoler P, Taiuti M, Taylor S, Tedeschi D, Tung TY, Vineyard MF, Vlassov A, Weller H, Weinstein LB, Welsh R, Weygand DP, Whisnant S, Witkowski M, Wolin E, Yegneswaran A, Yun J, Zhou Z, and Zhao J

Abstract

New cross sections for the reaction e p-->e p eta are reported for total center of mass energy W = 1.5--1.86 GeV and invariant momentum transfer Q2 = 0.25--1.5 (GeV/c)(2). This large kinematic range allows extraction of important new information about response functions, photocouplings, and eta N coupling strengths of baryon resonances. Newly observed structure at W approximately 1.65 GeV is shown to come from interference between S and P waves and can be interpreted with known resonances. Improved values are derived for the photon coupling amplitude for the S11(1535) resonance.

Published
2001
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