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43 results on '"Hammann, Ch."'

1. Polarization observables in double neutral pion photoproduction

Author

Collaboration, CBELSA/TAPS, Seifen, T., Hartmann, J., Afzal, F., Anisovich, A. V., Beck, R., Becker, M., Berlin, A., Bichow, M., Brinkmann, K. -Th., Crede, V., Dieterle, M., Dutz, H., Eberhardt, H., Elsner, D., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gottschall, M., Grüner, M., Görtz, St., Gutz, E., Hammann, Ch., Hannappel, J., Herick, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jahn, O., Jude, T., Käser, A., Kaiser, D., Kalinowsky, H., Kalischewski, F., Klassen, P., Keshelashvili, I., Klein, F., Klempt, E., Koop, K., Krusche, B., Lang, M., Mahlberg, Ph., Makonyi, K., Messi, F., Metag, V., Meyer, W., Müller, J., Müllers, J., Nanova, M., Nikonov, K., Nikonov, V. A., Novotny, R., Reeve, S., Roth, B., Reicherz, G., Rostomyan, T., Runkel, St., Sarantsev, A. V., Schmidt, Ch., Schmieden, H., Schmitz, R., Schultes, J., Sokhoyan, V., Stausberg, N., Thiel, A., Thoma, U., Urban, M., Urff, G., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Witthauer, L., and Wunderlich, Y.

Subjects
Nuclear Experiment
Abstract

Measurements of target asymmetries and double-polarization observables for the reaction $\gamma p\to p\pi^0\pi^0$ are reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility (Bonn University) using the Bonn frozen-spin butanol (C$_4$H$_9$OH) target, which provided transversely polarized protons. Linearly polarized photons were produced via bremsstrahlung off a diamond crystal. The data cover the photon energy range from $E_{\gamma}$=650 MeV to $E_{\gamma}$=2600 MeV and nearly the complete angular range. The results have been included in the BnGa partial wave analysis. Experimental results and the fit agree very well. Observed systematic differences in the branching ratios for decays of $N^*$ and $\Delta^*$ resonances are attributed to the internal structure of these excited nucleon states. Resonances which can be assigned to SU(6)$\times$O(3) two-oscillator configurations show larger branching ratios to intermediate states with non-zero intrinsic orbital angular momenta than resonances assigned to one-oscillator configurations., Comment: 21 pages, 27 figures

Published
2022

2. Observation of a structure in the M$_{p\eta}$ invariant mass distribution near 1700 MeV/$c^2$ in the $\mathbf{\gamma p \rightarrow p \pi^0 \eta} $ reaction

Author

Metag, V., Nanova, M., Hartmann, J., Mahlberg, P., Afzal, F., Bartels, C., Bayadilov, D., Beck, R., Becker, M., Blanke, E., Brinkmann, K. -T., Ciupka, S., Crede, V., Dieterle, M., Dutz, H., Elsner, D., Frommberger, F., Gridnev, A., Gottschall, M., Grüner, M., Hammann, Ch., Hannappel, J., Hillert, W., Hoff, J., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kalinowsky, H., Kalischewski, F., Keshelashvili, I., Ketzer, B., Klassen, P., Klein, F., Koop, K., Kroenert, P., Krusche, B., Lang, M., Lopatin, I., Messi, F., Meyer, W., Mitlasóczky, B., Müller, J., Müllers, J., Nikonov, V., Novinsky, V., Novotny, R., Piontek, D., Reicherz, G., Richter, L., Rostomyan, T., Runkel, S., Salisbury, B., Sarantsev, A., Schaab, D., Schmidt, Ch., Schmieden, H., Schultes, J., Seifen, T., Sokhoyan, V., Sowa, C., Spieker, K., Stausberg, N., Thiel, A., Thoma, U., Triffterer, T., Urban, M., Urff, G., van Pee, H., Wagner, M., Walther, D., Wendel, Ch., Werthmüller, D., Wiedner, U., Wilson, A., Winnebeck, A., Witthauer, L., and Wunderlich, Y.

Subjects
Nuclear Experiment, Nuclear Theory
Abstract

The reaction $\gamma p \rightarrow p \pi^0 \eta$ has been studied with the CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold up to 3.1 GeV. This paper has been motivated by the recently claimed observation of a narrow structure in the M$_{N\eta}$ invariant mass distribution at a mass of 1678 MeV/$c^2$. The existence of this structure cannot be confirmed in the present work. Instead, for E$_{\gamma}$ = 1400 - 1500 MeV and the cut M$_{p\pi^0} \le 1190 $ MeV/$c^2$ a statistically significant structure in the M$_{p\eta}$ invariant mass distribution near 1700 MeV/$c^2$ is observed with a width of $\Gamma\approx 35$ MeV/$c^2$ while the mass resolution is $\sigma_{res}$ = 5 MeV/$c^2$. Increasing the incident photon energy from 1420 to 1540 MeV this structure shifts in mass from $\approx$ 1700MeV/c$^2$ to $\approx$ 1725 MeV/$c^2$; the width increases to about 50 MeV/$c^2$ and decreases thereafter. The cross section associated with this structure reaches a maximum of $\approx$ 100 nb around E$_{\gamma} \approx$ 1490 MeV (W $\approx $ 1920 MeV), which coincides with the $p a_0$ threshold. Three scenarios are discussed which might be the origin of this structure in the M$_{p\eta}$ invariant mass distribution. The most likely interpretation is that it is due to a triangular singularity in the $\gamma p \rightarrow p a_0 \rightarrow p \pi^0 \eta$ reaction, Comment: 16 pages, 18 figure

Published
2021
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3. Measurement of the Helicity Asymmetry $E$ for the reaction $ \gamma p\to \pi^0 p$

Author

collaboration, CBELSA/TAPS, Gottschall, M., Afzal, F., Anisovich, A. V., Bayadilov, D., Beck, R., Bichow, M., Brinkmann, K. -Th., Crede, V., Dieterle, M., Dietz, F., Dutz, H., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Gridnev, A., Grüner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kammer, S., Kalinowsky, H., Keshelashvili, I., Klassen, P., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Mahlberg, P., Makonyi, K., Metag, V., Meyer, W., Müller, J., Müllers, J., Nanova, M., Nikonov, V., Novotny, R., Piontek, D., Reicherz, G., Rostomyan, T., Sarantsev, A., Schmidt, Ch., Schmieden, H., Seifen, T., Sokhoyan, V., Spieker, K., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Werthmüller, D., Wiedner, U., Wilson, A., Winnebeck, A., Witthauer, L., and Wunderlich, Y.

Subjects
Nuclear Experiment
Abstract

A measurement of the double-polarization observable $E$ for the reaction $\gamma p\to \pi^0 p$ is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C$_4$H$_9$OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from $E_\gamma =600$~MeV to $E_\gamma =2310$~MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses., Comment: 21 pages

Published
2019

4. The {\eta}'-carbon potential at low meson momenta

Author

Nanova, M., Friedrich, S., Metag, V., Paryev, E. Ya., Afzal, F. N., Bayadilov, D., Bantes, B., Beck, R., Becker, M., Böse, S., Brinkmann, K. -T., Crede, V., Drexler, P., Eberhardt, H., Elsner, D., Frommberger, F., Funke, Ch., Gottschall, M., Grüner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kaiser, D., Kalischewski, F., Keshelashvili, I., Klein, F., Koop, K., Krusche, B., Lang, M., Makonyi, K., Messi, F., Müller, J., Müllers, J., Piontek, D., Rostomyan, T., Schaab, D., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Sowa, C., Spieker, K., Thiel, A., Thoma, U., Triffterer, T., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Werthmüller, D., Wiedner, U., Wilson, A., Witthauer, L., Wunderlich, Y., and Zaunick, H. -G.

Subjects
Nuclear Experiment
Abstract

The production of $\eta^\prime$ mesons in coincidence with forward-going protons has been studied in photon-induced reactions on $^{12}$C and on a liquid hydrogen (LH$_2$) target for incoming photon energies of 1.3-2.6 GeV at the electron accelerator ELSA. The $\eta^\prime$ mesons have been identified via the $\eta^\prime\rightarrow \pi^0 \pi^0\eta \rightarrow 6 \gamma$ decay registered with the CBELSA/TAPS detector system. Coincident protons have been identified in the MiniTAPS BaF$_2$ array at polar angles of $2^{\circ} \le \theta _{p} \le 11^{\circ}$. Under these kinematic constraints the $\eta^\prime$ mesons are produced with relatively low kinetic energy ($\approx$ 150 MeV) since the coincident protons take over most of the momentum of the incident-photon beam. For the C-target this allows the determination of the real part of the $\eta^\prime$-carbon potential at low meson momenta by comparing with collision model calculations of the $\eta^\prime$ kinetic energy distribution and excitation function. Fitting the latter data for $\eta^\prime$ mesons going backwards in the center-of-mass system yields a potential depth of V = $-$(44 $\pm$ 16(stat)$\pm$15(syst)) MeV, consistent with earlier determinations of the potential depth in inclusive measurements for average $\eta^\prime$ momenta of $\approx$ 1.1 GeV/$c$. Within the experimental uncertainties, there is no indication of a momentum dependence of the $\eta^\prime$-carbon potential. The LH$_2$ data, taken as a reference to check the data analysis and the model calculations, provide differential and integral cross sections in good agreement with previous results for $\eta^\prime$ photoproduction off the free proton., Comment: 9 pages, 13 figures. arXiv admin note: text overlap with arXiv:1608.06074

Published
2018
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5. Photoproduction of eta mesons from the neutron: cross sections and double polarization observable E

Author

Witthauer, L., Dieterle, M., Afzal, F., Anisovich, A. V., Bantes, B., Bayadilov, D., Beck, R., Bichow, M., Brinkmann, K. -T., Böse, S., Challand, Th., Crede, V., Dutz, H., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Goertz, St., Gottschall, M., Gridnev, A., Grüner, M., Gutzınst, E., Hammann, D., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kaiser, D., Kalinowsky, H., Kalischewski, F., Kammer, S., Käser, A., Keshelashvili, I., Klassen, P., Kleber, V., Klein, F., Koop, K., Krusche, B., Lang, M., Lopatin, I., Mahlberg, Ph., Makonyi, K., Metag, V., Meyer, W., Müller, J., Müllers, J., Nanova, M., Nikonov, V., Piontek, D., Reicherz, G., Rostomyan, T., Sarantsev, A., Schmidt, Ch., Schmieden, H., Seifen, T., Sokhoyan, V., Spieker, K., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walford, N. K., Walther, D., Wendel, Ch., Werthmüller, D., Wilson, A., and Winnebeck, A.

Subjects
Nuclear Experiment
Abstract

Photoproduction of $\eta$ mesons from neutrons} \abstract{Results from measurements of the photoproduction of $\eta$ mesons from quasifree protons and neutrons are summarized. The experiments were performed with the CBELSA/TAPS detector at the electron accelerator ELSA in Bonn using the $\eta\to3\pi^{0}\to6\gamma$ decay. A liquid deuterium target was used for the measurement of total cross sections and angular distributions. The results confirm earlier measurements from Bonn and the MAMI facility in Mainz about the existence of a narrow structure in the excitation function of $\gamma n\rightarrow n\eta$. The current angular distributions show a forward-backward asymmetry, which was previously not seen, but was predicted by model calculations including an additional narrow $P_{11}$ state. Furthermore, data obtained with a longitudinally polarized, deuterated butanol target and a circularly polarized photon beam were analyzed to determine the double polarization observable $E$. Both data sets together were also used to extract the helicity dependent cross sections $\sigma_{1/2}$ and $\sigma_{3/2}$. The narrow structure in the excitation function of $\gamma n\rightarrow n\eta$ appears associated with the helicity-1/2 component of the reaction.

Published
2017
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6. Momentum dependence of the imaginary part of the $\omega$- and $\eta^\prime$-nucleus optical potential

Author

Friedrich, S., Nanova, M., Metag, V., Afzal, F. N., Bayadilov, D., Bantes, B., Beck, R., Becker, M., Böse, S., Brinkmann, K. -T., Crede, V., Drexler, P., Eberhardt, H., Elsner, D., Frommberger, F., Funke, Ch., Gottschall, M., Grüner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kaiser, D., Kalischewski, F., Keshelashvili, I., Klein, F., Koop, K., Krusche, B., Lang, M., Makonyi, K., Messi, F., Müller, J., Müllers, J., Piontek, D. -M., Rostomyan, T., Schaab, D., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Sowa, C., Spieker, K., Thiel, A., Thoma, U., Triffterer, T., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Werthmüller, D., Wiedner, U., Wilson, A., Witthauer, L., Wunderlich, Y., and Zaunick, H. -G.

Subjects
Nuclear Experiment
Abstract

The photoproduction of $\omega$ and $\eta^\prime$ mesons off carbon and niobium nuclei has been measured as a function of the meson momentum for incident photon energies of 1.2-2.9 GeV at the electron accelerator ELSA. The mesons have been identified via the $\omega \rightarrow \pi^0 \gamma \rightarrow 3 \gamma$ and $\eta^\prime\rightarrow \pi^0 \pi^0\eta \rightarrow 6 \gamma$ decays, respectively, registered with the CBELSA/TAPS detector system. From the measured meson momentum distributions the momentum dependence of the transparency ratio has been determined for both mesons. Within a Glauber analysis the in-medium $\omega$ and $\eta^\prime$ widths and the corresponding absorption cross sections have been deduced as a function of the meson momentum. The results are compared to recent theoretical predictions for the in-medium $\omega$ width and $\eta^\prime$-N absorption cross sections. The energy dependence of the imaginary part of the $\omega$- and $\eta^\prime$-nucleus optical potential has been extracted. The finer binning of the present data compared to the existing data allows a more reliable extrapolation towards the production threshold. The modulus of the imaginary part of the $\eta^\prime$ nucleus potential is found to be about three times smaller than recently determined values of the real part of the $\eta^\prime$-nucleus potential, which makes the $\eta^\prime$ meson a suitable candidate for the search for meson-nucleus bound states. For the $\omega$ meson, the modulus of the imaginary part near threshold is comparable to the modulus of the real part of the potential. As a consequence, only broad structures can be expected which makes the observation of $\omega$ mesic states very difficult experimentally., Comment: 10 pages, 8 figures

Published
2016
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7. Determination of the real part of the {\eta}'-Nb optical potential

Author

Nanova, M., Friedrich, S., Metag, V., Paryev, E. Ya., Afzal, F. N., Bayadilov, D., Beck, R., Becker, M., Böse, S., Brinkmann, K. -T., Crede, V., Elsner, D., Frommberger, F., Grtuner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, P., Honisch, Ch., Jude, T., Kalischewski, F., Keshelashvili, I., Klein, F., Koop, K., Krusche, B., Lang, M., Makonyi, K., Messi, F., Müller, J., Müllers, J., Piontek, D. M., Rostomyan, T., Schaab, D., Schmidt, C., Schmieden, H., Schmitz, R., Seifen, T., Sowa, C., Spieker, K., Thiel, A., Thoma, U., Tristerer, T., Urban, M., van Pee, H., Walther, D., Wendel, C., Werthmüller, D., Wiedner, U., Wilson, A., Witthauer, L., Wunderlich, Y., and Zaunick, H. -G.

Subjects
Nuclear Experiment
Abstract

The excitation function and momentum distribution of {\eta}' mesons have been measured in photoproduction off 93^Nb in the energy range of 1.2-2.9 GeV. The experiment has been performed with the combined Crystal Barrel and MiniTAPS detector system, using tagged photon beams from the ELSA electron accelerator. Information on the sign and magnitude of the real part of the {\eta}'-Nb potential has been extracted from a comparison of the data with model calculations. An attractive potential of -(41 \pm 10(stat) \pm 15(syst)) MeV depth at normal nuclear matter density is deduced within model uncertainties. This value is consistent with the potential depth of -(37 \pm 10(stat) \pm 10(syst)) MeV obtained in an earlier measurement for a light nucleus (carbon). This relatively shallow {\eta}'-nucleus potential will make the search for {\eta}'-nucleus bound states more difficult., Comment: 9 pages, 6 figures

Published
2016
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8. Double-polarization observable G in neutral-pion photoproduction off the proton

Author

Thiel, A., Eberhardt, H., Lang, M., Afzal, F., Anisovich, A. V., Bantes, B., Bayadilov, D., Beck, R., Bichow, M., Brinkmann, K. -T., Böse, S., Crede, V., Dieterle, M., Dutz, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Goertz, St., Gottschall, M., Gridnev, A., Grüner, M., Gutz, E., Hammann, D., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kaiser, D., Kalinowsky, H., Kalischewski, F., Kammer, S., Keshelashvili, I., Klassen, P., Kleber, V., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lopatin, I., Mahlberg, Ph., Makonyi, K., Metag, V., Meyer, W., Müller, J., Müllers, J., Nanova, M., Nikonov, V., Piontek, D., Reeve, S., Reicherz, G., Runkel, S., Sarantsev, A., Schmidt, Ch., Schmieden, H., Seifen, T., Sokhoyan, V., Spieker, K., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wilson, A., Winnebeck, A., and Witthauer, L.

Subjects
Nuclear Experiment
Abstract

This paper reports on a measurement of the double-polarization observable G in $\pi^0$ photoproduction off the proton using the CBELSA/TAPS experiment at the ELSA accelerator in Bonn. The observable G is determined from reactions of linearly-polarized photons with longitudinally-polarized protons. The polarized photons are produced by bremsstrahlung off a properly oriented diamond radiator. A frozen spin butanol target provides the polarized protons. The data cover the photon energy range from 617 to 1325 MeV and a wide angular range. The experimental results for G are compared to predictions by the Bonn-Gatchina (BnGa), J\"ulich-Bonn (J\"uBo), MAID and SAID partial wave analyses. Implications of the new data for the pion photoproduction multipoles are discussed.

Published
2016
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9. The polarization observables T, P, and H and their impact on $\gamma p \to p\pi^0$ multipoles

Author

Hartmann, J., Dutz, H., Anisovich, A. V., Bayadilov, D., Beck, R., Becker, M., Beloglazov, Y., Berlin, A., Bichow, M., Böse, S., Brinkmann, K. -Th., Crede, V., Dieterle, M., Eberhardt, H., Elsner, D., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gottschall, M., Gridnev, A., Grüner, M., Görtz, St., Gutz, E., Hammann, Ch., Hannappel, J., Hannen, V., Herick, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jahn, O., Jude, T., Käser, A., Kaiser, D., Kalinowsky, H., Kalischewski, F., Klassen, P., Keshelashvili, I., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Makonyi, K., Messi, F., Metag, V., Meyer, W., Müller, J., Nanova, M., Nikonov, V., Novinski, D., Novotny, R., Piontek, D., Reeve, S., Rosenbaum, Ch., Roth, B., Reicherz, G., Rostomyan, T., Runkel, St., Sarantsev, A., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Thämer, Ph., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Winnebeck, A., and Witthauer, L.

Subjects
Nuclear Experiment
Abstract

Data on the polarization observables T, P, and H for the reaction $\gamma p\to p\pi^0$ are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction.

Published
2015
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10. Measurement of double polarisation asymmetries in $\omega$-photoproduction

Author

Eberhardt, H., Jude, T. C., Schmieden, H., Anisovich, A. V., Bantes, B., Bayadilov, D., Beck, R., Beloglazov, Yu., Bichow, M., Boese, S., Brinkmann, K. -Th., Challand, Th., Crede, V., Diez, F., Drexler, P., Dutz, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gottschall, M., Gridnev, A., Gruener, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jaegle, I., Kaiser, D., Kalinowsky, H., Kalischewski, F., Kammer, S., Keshelashvili, I., Kleber, V., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Maghrbi, Y., Makonyi, K., Metag, V., Meyer, W., Mueller, J., Nanova, M., Nikonov, V., Novotny, R., Piontek, D., Reeve, S., Reicherz, G., Rostomyan, T., Runkel, S., Sarantsev, A., Schaepe, St., Schmidt, Ch., Schmitz, R., Seifen, T., Sokhoyan, V., Sumachev, V., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., and Winnebeck, A.

Subjects
Nuclear Experiment
Abstract

The first measurements of the beam-target-helicity-asymmetries $E$ and $G$ in the photoproduction of $\omega$-mesons off protons at the CBELSA/TAPS experiment are reported. $E$ ($G$) was measured using circularly (linearly) polarised photons and a longitudinally polarised target. $E$ was measured over the photon energy range from close to threshold ($E_\gamma = 1108$~MeV) to $E_\gamma = 2300$~MeV and $G$ at a single energy interval of $1108 < E_\gamma <1300$~MeV. Both measurements cover the full solid angle. The observables $E$ and $G$ are highly sensitive to the contribution of baryon resonances, with $E$ acting as a helicity filter in the $s$-channel. The new results indicate significant $s$-channel resonance contributions together with contributions from $t$-channel exchange processes. A partial wave analysis reveals strong contributions from the partial waves with spin-parity $J^P=3/2^+, 5/2^+$, and $3/2^-$., Comment: 6 pages, 6 figures

Published
2015
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11. The N(1520) 3/2- helicity amplitudes from an energy-independent multipole analysis based on new polarization data on photoproduction of neutral pions

Author

Hartmann, J., Dutz, H., Anisovich, A. V., Bayadilov, D., Beck, R., Becker, M., Beloglazov, Y., Berlin, A., Bichow, M., Böse, S., Brinkmann, K. -Th., Crede, V., Dieterle, M., Eberhardt, H., Elsner, D., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gottschall, M., Gridnev, A., Grüner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hannen, V., Herick, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jahn, O., Jude, T., Käser, A., Kaiser, D., Kalinowsky, H., Kalischewski, F., Klassen, P., Keshelashvili, I., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Makonyi, K., Messi, F., Metag, V., Meyer, W., Müller, J., Nanova, M., Nikonov, V., Novinski, D., Novotny, R., Piontek, D., Rosenbaum, C., Roth, B., Reicherz, G., Rostomyan, T., Sarantsev, A., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Thämer, Ph., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Winnebeck, A., Witthauer, L., and Wunderlich, Y.

Subjects
Nuclear Experiment
Abstract

New data on the polarization observables T, P, and H for the reaction $\gamma p \to p\pi^0$ are reported. The results are extracted from azimuthal asymmetries when a transversely polarized butanol target and a linearly polarized photon beam are used. The data were taken at the Bonn electron stretcher accelerator ELSA using the CBELSA/TAPS detector. These and earlier data are used to perform a truncated energy-independent partial wave analysis in sliced-energy bins. This energy-independent analysis is compared to the results from energy-dependent partial wave analyses.

Published
2014
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12. Experimental constraints on the $\omega$-nucleus real potential

Author

Friedrich, S., Makonyi, K., Metag, V., Bayadilov, D., Bantes, B., Beck, R., Beloglazov, Y. A., Böse, S., Brinkmann, K. -T., Challand, Th., Crede, V., Dahlke, T., Dietz, F., Drexler, P., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Frommberger, F., Funke, Ch., Gottschall, M., Gridnev, A., Grüner, M., Gutz, E., Hammann, Ch., Hammann, D., Hannappel, J., Hartmann, J., Hillert, W., Hirenzaki, S., Hoffmeister, P., Honisch, Ch., Jaegle, I., Kaiser, D., Kalinowsky, H., Kammer, S., Keshelashvili, I., Kleber, V., Klein, F., Krusche, B., Lang, M., Lopatin, I. V., Maghrbi, Y., Nanova, M., Nagahiro, H., Müller, J., Odenthal, T., Piontek, D., Rostomyan, T., Schaepe, S., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Thiel, A., Thoma, U., van Pee, H., Walther, D., Weil, J., Wendel, Ch., Wiedner, U., Wilson, A., Winnebeck, A., and Zenke, F.

Subjects
Nuclear Experiment
Abstract

In a search for $\omega$ mesic states, the production of $\omega$-mesons in coincidence with forward going protons has been studied in photon induced reactions on $^{12}$C for incident photon energies of 1250 - 3100 MeV. The $\pi^0 \gamma$ pairs from decays of bound or quasi-free $\omega$-mesons have been measured with the CBELSA/TAPS detector system in coincidence with protons registered in the MiniTAPS forward array. Structures in the total energy distribution of the $\pi^0 \gamma$ pairs, which would indicate the population and decay of bound $\omega~^{11}$B states, are not observed. The $\pi^0 \gamma$ cross section of 0.3 nb/MeV/sr observed in the bound state energy regime between -100 and 0 MeV may be accounted for by yield leaking into the bound state regime because of the large in-medium width of the $\omega$-meson. A comparison of the measured total energy distribution with calculations suggests the real part $V_0$ of the $\omega~^{11}$B potential to be small and only weakly attractive with $V_0(\rho=\rho_0) = -15\pm$ 35(stat) $\pm$20(syst) MeV in contrast to some theoretical predictions of attractive potentials with a depth of 100 - 150 MeV., Comment: 13 pages, 8 figures

Published
2014
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13. First measurement of the helicity asymmetry for $\gamma p\rightarrow p\pi^0$ in the resonance region

Author

Gottschall, M., Anisovich, A. V., Bantes, B., Bayadilov, D., Beck, R., Bichow, M., Böse, S., Brinkmann, K. -Th., Challand, Th., Crede, V., Dietz, F., Dutz, H., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gridnev, A., Grüner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jaegle, I., Kaiser, D., Kalinowsky, H., Kammer, S., Keshelashvili, I., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Maghrbi, Y., Makonyi, K., Metag, V., Meyer, W., Müller, J., Nanova, M., Nikonov, V., Novotny, R., Piontek, D., Reicherz, G., Rostomyan, T., Sarantsev, A., Schaepe, St., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., and Winnebeck, A.

Subjects
Nuclear Experiment
Abstract

The first measurement of the helicity dependence of the photoproduction cross section of single neutral pions off protons is reported for photon energies from 600 to 2300\,MeV, covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, and BnGa partial wave analyses. Strikingly large differences between data and predictions are observed which are traced to differences in the helicity amplitudes of well known and established resonances. Precise values for the helicity amplitudes of several resonances are reported.

Published
2013
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14. Determination of the {\eta}'-nucleus optical potential

Author

Nanova, M., Metag, V., Paryev, E. Ya., Bayadilov, D., Bantes, B., Beck, R., Beloglazov, Y. A., Böse, S., Brinkmann, K. -T., Challand, Th., Crede, V., Dahlke, T., Dietz, F., Drexler, P., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, S., Frommberger, F., Funke, Ch., Gottschall, M., Gridnev, A., Grüner, M., Gutz, E., Hammann, Ch., Hammann, D., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, P., Honisch, Ch., Jaegle, I., Kaiser, D., Kalinowsky, H., Kammer, S., Keshelashvili, I., Kleber, V., Klein, F., Klempt, E., Krusche, B., Lang, M., Lopatin, I. V., Maghrbi, Y., Makonyi, K., Müller, J., Odenthal, T., Piontek, D., Schaepe, S., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Thiel, A., Thoma, U., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Winnebeck, A., and Zenke, F.

Subjects
Nuclear Experiment
Abstract

The excitation function and momentum distribution of $\eta^\prime$ mesons have been measured in photon induced reactions on $^{12}{}$C in the energy range of 1250-2600 MeV. The experiment was performed with tagged photon beams from the ELSA electron accelerator using the Crystal Barrel and TAPS detectors. The data are compared to model calculations to extract information on the sign and magnitude of the real part of the $\eta^\prime$-nucleus potential. Within the model, the comparison indicates an attractive potential of -($37 \pm 10(stat)\pm10(syst)$) MeV depth at normal nuclear matter density. Since the modulus of this depth is larger than the modulus of the imaginary part of the $\eta^\prime$-nucleus potential of -($10\pm2.5$) MeV, determined by transparency ratio measurements, a search for resolved $\eta^\prime$-bound states appears promising., Comment: 13 pages, 6 figures

Published
2013
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15. Well-established nucleon resonances revisited by double-polarization measurements

Author

Thiel, A., Anisovich, A. V., Bayadilov, D., Bantes, B., Beck, R., Beloglazov, Yu., Bichow, M., Böse, S., Brinkmann, K. -Th., Challand, Th., Crede, V., Dietz, F., Drexler, P., Dutz, H., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gottschall, M., Grüner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jaegle, I., Jürgensen, I., Kaiser, D., Kalinowsky, H., Kalischewski, F., Kammer, S., Keshelashvili, I., Kleber, V., Klein, F., Klempt, E., Krusche, B., Lang, M., Lopatin, I., Maghrbi, Y., Makonyi, K., Metag, V., Meyer, W., Müller, J., Nanova, M., Nikonov, V., Novotny, R., Piontek, D., Reicherz, G., Sarantsev, A., Schmidt, Ch., Schmieden, H., Seifen, T., Sokhoyan, V., Sumachev, V., Thoma, U., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Winnebeck, A., and Wunderlich, Y.

Subjects
Nuclear Experiment
Abstract

The first measurement is reported of the double-polarization observable G in photoproduction of neutral pions off protons, covering the photon energy range from 620 to 1120 MeV and the full solid angle. G describes the correlation between the photon polarization plane and the scattering plane for protons polarized along the direction of the incoming photon. The observable is highly sensitive to contributions from baryon resonances. The new results are compared to the predictions from SAID, MAID, and BnGa partial wave analyses. In spite of the long-lasting efforts to understand {\gamma}p -> p{\pi} 0 as the simplest photoproduction reaction, surprisingly large differences between the new data and the latest predictions are observed which are traced to different contributions of the N (1535) with spin-parity J^P = 1/2^- and N (1520) with J^P = 3/2^- . In the third resonance region, where N (1680) with J^P = 5/2^+ production dominates, the new data are reasonably close to the predictions., Comment: Submitted for publication in PRL

Published
2012
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16. Measurement of the helicity asymmetry E for the reaction γp→π0p: The CBELSA/TAPS Collaboration

Author

Gottschall, M., Afzal, F., Anisovich, A. V., Bayadilov, D., Beck, R., Bichow, M., Brinkmann, K. Th., Crede, V., Dieterle, M., Dietz, F., Dutz, H., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Gridnev, A., Grüner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kammer, S., Kalinowsky, H., Keshelashvili, I., Klassen, P., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Mahlberg, P., Makonyi, K., Metag, V., Meyer, W., Müller, J., Müllers, J., Nanova, M., Nikonov, V., Novotny, R., Piontek, D., Reicherz, G., Rostomyan, T., Sarantsev, A., Schmidt, Ch., Schmieden, H., Seifen, T., Sokhoyan, V., Spieker, K., Thiel, A., Thoma, U., Urban, M., Pee, H. van, Walther, D., Wendel, Ch., Werthmüller, D., Wiedner, U., Wilson, A., Winnebeck, A., Witthauer, L., and Wunderlich, Y.

Published
2021
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17. Double-polarization observable G in neutral-pion photoproduction off the proton

Author

Thiel, A., Eberhardt, H., Lang, M., Afzal, F., Anisovich, A. V., Bantes, B., Bayadilov, D., Beck, R., Bichow, M., Brinkmann, K. -T., Böse, S., Crede, V., Dieterle, M., Dutz, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Goertz, St., Gottschall, M., Gridnev, A., Grüner, M., Gutz, E., Hammann, D., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kaiser, D., Kalinowsky, H., Kalischewski, F., Kammer, S., Keshelashvili, I., Klassen, P., Kleber, V., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lopatin, I., Mahlberg, Ph., Makonyi, K., Metag, V., Meyer, W., Müller, J., Müllers, J., Nanova, M., Nikonov, V., Piontek, D., Reeve, S., Reicherz, G., Runkel, S., Sarantsev, A., Schmidt, Ch., Schmieden, H., Seifen, T., Sokhoyan, V., Spieker, K., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wilson, A., Winnebeck, A., Witthauer, L., and The CBELSA/TAPS Collaboration

Published
2017
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18. The η-carbon potential at low meson momenta

Author

The CBELSA/TAPS Collaboration, Nanova, M., Friedrich, S., Metag, V., Paryev, E. Ya., Afzal, F. N., Bayadilov, D., Bantes, B., Beck, R., Becker, M., Böse, S., Brinkmann, K. -T., Crede, V., Drexler, P., Eberhardt, H., Elsner, D., Frommberger, F., Funke, Ch., Gottschall, M., Grüner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kaiser, D., Kalischewski, F., Keshelashvili, I., Klein, F., Koop, K., Krusche, B., Lang, M., Makonyi, K., Messi, F., Müller, J., Müllers, J., Piontek, D., Rostomyan, T., Schaab, D., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Sowa, C., Spieker, K., Thiel, A., Thoma, U., Triffterer, T., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Werthmüller, D., Wiedner, U., Wilson, A., Witthauer, L., Wunderlich, Y., and Zaunick, H. -G.

Published
2018
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19. Polarization observables in double neutral pion photoproduction

Author

TAPS Collaboration, Seifen, T., Hartmann, J., Afzal, F., Anisovich, A. V., Beck, R., Becker, M., Berlin, A., Bichow, M., Brinkmann, K. -Th., Crede, V., Dieterle, M., Dutz, H., Eberhardt, H., Elsner, D., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gottschall, M., Grüner, M., Görtz, St., Gutz, E., Hammann, Ch., Hannappel, J., Herick, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jahn, O., Jude, T., Käser, A., Kaiser, D., Kalinowsky, H., Kalischewski, F., Klassen, P., Keshelashvili, I., Klein, F., Klempt, E., Koop, K., Krusche, B., Lang, M., Mahlberg, Ph., Makonyi, K., Messi, F., Metag, V., Meyer, W., Müller, J., Müllers, J., Nanova, M., Nikonov, K., Nikonov, V. A., Novotny, R., Reeve, S., Roth, B., Reicherz, G., Rostomyan, T., Runkel, St., Sarantsev, A. V., Schmidt, Ch., Schmieden, H., Schmitz, R., Schultes, J., Sokhoyan, V., Stausberg, N., Thiel, A., Thoma, U., Urban, M., Urff, G., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Witthauer, L., and Wunderlich, Y.

Subjects
FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

Measurements of target asymmetries and double-polarization observables for the reaction $\gamma p\to p\pi^0\pi^0$ are reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility (Bonn University) using the Bonn frozen-spin butanol (C$_4$H$_9$OH) target, which provided transversely polarized protons. Linearly polarized photons were produced via bremsstrahlung off a diamond crystal. The data cover the photon energy range from $E_{\gamma}$=650 MeV to $E_{\gamma}$=2600 MeV and nearly the complete angular range. The results have been included in the BnGa partial wave analysis. Experimental results and the fit agree very well. Observed systematic differences in the branching ratios for decays of $N^*$ and $\Delta^*$ resonances are attributed to the internal structure of these excited nucleon states. Resonances which can be assigned to SU(6)$\times$O(3) two-oscillator configurations show larger branching ratios to intermediate states with non-zero intrinsic orbital angular momenta than resonances assigned to one-oscillator configurations., Comment: 21 pages, 27 figures

Published
2022

20. Observation of a structure in the $$M_{p\eta }$$ invariant mass distribution near 1700 $$\hbox {MeV}/\hbox {c}^2$$ in the $$\gamma \mathbf {p \rightarrow p \pi ^0 \eta } $$ reaction

Author

Metag, V., primary, Nanova, M., additional, Hartmann, J., additional, Mahlberg, P., additional, Afzal, F., additional, Bartels, C., additional, Bayadilov, D., additional, Beck, R., additional, Becker, M., additional, Blanke, E., additional, Brinkmann, K.-T., additional, Ciupka, S., additional, Crede, V., additional, Dieterle, M., additional, Dutz, H., additional, Elsner, D., additional, Frommberger, F., additional, Gridnev, A., additional, Gottschall, M., additional, Grüner, M., additional, Hammann, Ch., additional, Hannappel, J., additional, Hillert, W., additional, Hoff, J., additional, Hoffmeister, Ph., additional, Honisch, Ch., additional, Jude, T., additional, Kalinowsky, H., additional, Kalischewski, F., additional, Keshelashvili, I., additional, Ketzer, B., additional, Klassen, P., additional, Klein, F., additional, Koop, K., additional, Kroenert, P., additional, Krusche, B., additional, Lang, M., additional, Lopatin, I., additional, Messi, F., additional, Meyer, W., additional, Mitlasóczky, B., additional, Müller, J., additional, Müllers, J., additional, Nikonov, V., additional, Novinsky, V., additional, Novotny, R., additional, Piontek, D., additional, Reicherz, G., additional, Richter, L., additional, Rostomyan, T., additional, Runkel, S., additional, Salisbury, B., additional, Sarantsev, A., additional, Schaab, D., additional, Schmidt, Ch., additional, Schmieden, H., additional, Schultes, J., additional, Seifen, T., additional, Sokhoyan, V., additional, Sowa, C., additional, Spieker, K., additional, Stausberg, N., additional, Thiel, A., additional, Thoma, U., additional, Triffterer, T., additional, Urban, M., additional, Urff, G., additional, van Pee, H., additional, Wagner, M., additional, Walther, D., additional, Wendel, Ch., additional, Werthmüller, D., additional, Wiedner, U., additional, Wilson, A., additional, Winnebeck, A., additional, Witthauer, L., additional, and Wunderlich, Y., additional

Published
2021
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21. Observation of a structure in the M$_{p��}$ invariant mass distribution near 1700 MeV/$c^2$ in the $\mathbf{��p \rightarrow p ��^0 ��} $ reaction

Author

Metag, V., Nanova, M., Hartmann, J., Mahlberg, P., Afzal, F., Bartels, C., Bayadilov, D., Beck, R., Becker, M., Blanke, E., Brinkmann, K. -T., Ciupka, S., Crede, V., Dieterle, M., Dutz, H., Elsner, D., Frommberger, F., Gridnev, A., Gottschall, M., Gr��ner, M., Hammann, Ch., Hannappel, J., Hillert, W., Hoff, J., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kalinowsky, H., Kalischewski, F., Keshelashvili, I., Ketzer, B., Klassen, P., Klein, F., Koop, K., Kroenert, P., Krusche, B., Lang, M., Lopatin, I., Messi, F., Meyer, W., Mitlas��czky, B., M��ller, J., M��llers, J., Nikonov, V., Novinsky, V., Novotny, R., Piontek, D., Reicherz, G., Richter, L., Rostomyan, T., Runkel, S., Salisbury, B., Sarantsev, A., Schaab, D., Schmidt, Ch., Schmieden, H., Schultes, J., Seifen, T., Sokhoyan, V., Sowa, C., Spieker, K., Stausberg, N., Thiel, A., Thoma, U., Triffterer, T., Urban, M., Urff, G., van Pee, H., Wagner, M., Walther, D., Wendel, Ch., Werthm��ller, D., Wiedner, U., Wilson, A., Winnebeck, A., Witthauer, L., and Wunderlich, Y.

Subjects
Nuclear Theory (nucl-th), Nuclear Theory, Physics::Accelerator Physics, FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

The reaction $��p \rightarrow p ��^0 ��$ has been studied with the CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold up to 3.1 GeV. This paper has been motivated by the recently claimed observation of a narrow structure in the M$_{N��}$ invariant mass distribution at a mass of 1678 MeV/$c^2$. The existence of this structure cannot be confirmed in the present work. Instead, for E$_��$ = 1400 - 1500 MeV and the cut M$_{p��^0} \le 1190 $ MeV/$c^2$ a statistically significant structure in the M$_{p��}$ invariant mass distribution near 1700 MeV/$c^2$ is observed with a width of $��\approx 35$ MeV/$c^2$ while the mass resolution is $��_{res}$ = 5 MeV/$c^2$. Increasing the incident photon energy from 1420 to 1540 MeV this structure shifts in mass from $\approx$ 1700MeV/c$^2$ to $\approx$ 1725 MeV/$c^2$; the width increases to about 50 MeV/$c^2$ and decreases thereafter. The cross section associated with this structure reaches a maximum of $\approx$ 100 nb around E$_�� \approx$ 1490 MeV (W $\approx $ 1920 MeV), which coincides with the $p a_0$ threshold. Three scenarios are discussed which might be the origin of this structure in the M$_{p��}$ invariant mass distribution. The most likely interpretation is that it is due to a triangular singularity in the $��p \rightarrow p a_0 \rightarrow p ��^0 ��$ reaction, 16 pages, 18 figure

Published
2021
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22. Measurement of the helicity asymmetry E for the reaction $$ \gamma p\rightarrow \pi ^0 p$$

Author

Gottschall, M., primary, Afzal, F., additional, Anisovich, A. V., additional, Bayadilov, D., additional, Beck, R., additional, Bichow, M., additional, Brinkmann, K. Th., additional, Crede, V., additional, Dieterle, M., additional, Dietz, F., additional, Dutz, H., additional, Eberhardt, H., additional, Elsner, D., additional, Ewald, R., additional, Fornet-Ponse, K., additional, Friedrich, St., additional, Frommberger, F., additional, Gridnev, A., additional, Grüner, M., additional, Gutz, E., additional, Hammann, Ch., additional, Hannappel, J., additional, Hartmann, J., additional, Hillert, W., additional, Hoffmeister, Ph., additional, Honisch, Ch., additional, Jude, T., additional, Kammer, S., additional, Kalinowsky, H., additional, Keshelashvili, I., additional, Klassen, P., additional, Klein, F., additional, Klempt, E., additional, Koop, K., additional, Krusche, B., additional, Kube, M., additional, Lang, M., additional, Lopatin, I., additional, Mahlberg, P., additional, Makonyi, K., additional, Metag, V., additional, Meyer, W., additional, Müller, J., additional, Müllers, J., additional, Nanova, M., additional, Nikonov, V., additional, Novotny, R., additional, Piontek, D., additional, Reicherz, G., additional, Rostomyan, T., additional, Sarantsev, A., additional, Schmidt, Ch., additional, Schmieden, H., additional, Seifen, T., additional, Sokhoyan, V., additional, Spieker, K., additional, Thiel, A., additional, Thoma, U., additional, Urban, M., additional, Pee, H. van, additional, Walther, D., additional, Wendel, Ch., additional, Werthmüller, D., additional, Wiedner, U., additional, Wilson, A., additional, Winnebeck, A., additional, Witthauer, L., additional, and Wunderlich, Y., additional

Published
2021
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23. Measurement of the Helicity Asymmetry $E$ for the reaction $ ��p\to ��^0 p$

Author

TAPS Collaboration, Gottschall, M., Afzal, F., Anisovich, A. V., Bayadilov, D., Beck, R., Bichow, M., Brinkmann, K. -Th., Crede, V., Dieterle, M., Dietz, F., Dutz, H., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Gridnev, A., Gr��ner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kammer, S., Kalinowsky, H., Keshelashvili, I., Klassen, P., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Mahlberg, P., Makonyi, K., Metag, V., Meyer, W., M��ller, J., M��llers, J., Nanova, M., Nikonov, V., Novotny, R., Piontek, D., Reicherz, G., Rostomyan, T., Sarantsev, A., Schmidt, Ch., Schmieden, H., Seifen, T., Sokhoyan, V., Spieker, K., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Werthm��ller, D., Wiedner, U., Wilson, A., Winnebeck, A., Witthauer, L., and Wunderlich, Y.

Subjects
Nuclear Theory, Physics::Accelerator Physics, FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

A measurement of the double-polarization observable $E$ for the reaction $��p\to ��^0 p$ is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C$_4$H$_9$OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from $E_��=600$~MeV to $E_��=2310$~MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses., 21 pages

Published
2019
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24. The $\eta^{\prime}$η-carbon potential at low meson momenta

Author

Nanova, M., Friedrich, S., Brinkmann, K. -T., Crede, V., Drexler, P., Eberhardt, H., Elsner, D., Frommberger, F., Funke, Ch., Gottschall, M., Grüner, M., Gutz, E., Metag, V., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jude, T., Kaiser, D., Kalischewski, F., Keshelashvili, I., Paryev, E. Ya., Klein, F., Koop, K., Krusche, B., Lang, M., Makonyi, K., Messi, F., Müller, J., Müllers, J., Piontek, D., Rostomyan, T., Afzal, F. N., Schaab, D., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Sowa, C., Spieker, K., Thiel, A., Thoma, U., Bayadilov, D., Triffterer, T., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Werthmüller, D., Wiedner, U., Wilson, A., Witthauer, L., Wunderlich, Y., Bantes, B., Zaunick, H. -G., Beck, R., Becker, M., and Böse, S.

Subjects
Nuclear Theory, High Energy Physics::Experiment, ddc:530, Nuclear Experiment
Abstract

The production of η′ mesons in coincidence with forward-going protons has been studied in photon-induced reactions on 12C and on a liquid hydrogen (LH2) target for incoming photon energies of 1.3-2.6 GeV at the electron accelerator ELSA. The η′ mesons have been identified via the η′→π0π0η→6γ decay registered with the CBELSA/TAPS detector system. Coincident protons have been identified in the MiniTAPS BaF2 array at polar angles of 2∘≤θp≤11∘. Under these kinematic constraints the η′ mesons are produced with relatively low kinetic energy (≈150 MeV) since the coincident protons take over most of the momentum of the incident-photon beam. For the C-target this allows the determination of the real part of the η′-carbon potential at low meson momenta by comparing with collision model calculations of the η′ kinetic energy distribution and excitation function. Fitting the latter data for η′ mesons going backwards in the center-of-mass system yields a potential depth of V=−(44±16(stat)±15(syst)) MeV, consistent with earlier determinations of the potential depth in inclusive measurements for average η′ momenta of ≈1.1 GeV/c. Within the experimental uncertainties, there is no indication of a momentum dependence of the η′-carbon potential. The LH2 data, taken as a reference to check the data analysis and the model calculations, provide differential and integral cross sections in good agreement with previous results for η′ photoproduction off the free proton.

Published
2018

25. Momentum dependence of the imaginary part of the ω - and η -nucleus optical potential

Author

Friedrich, S., Nanova, M., Metag, V., Afzal, F. N., Bayadilov, D., Bantes, B., Beck, R., Becker, M., Böse, S., Brinkmann, K. T., Crede, V., Drexler, P., Eberhardt, H., Elsner, D., Frommberger, F., Funke, Ch, Gottschall, M., Grüner, M., Gutz, E., Hammann, Ch, Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph, Honisch, Ch, Jude, T., Kaiser, D., Kalischewski, F., Keshelashvili, I., Klein, F., Koop, K., Krusche, B., Makonyi, K., Messi, F., Müller, J., Müllers, J., Piontek, D. M., Rostomyan, T., Schaab, D., Schmidt, Ch, Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Sowa, C., Spieker, K., Thiel, A., Thoma, U., Triffterer, T., Urban, M., van Pee, H., Walther, D., Wendel, Ch, Werthmüller, D., Wiedner, U., Witthauer, L., Wunderlich, Y., and Zaunick, H. G.

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment
Abstract

The photoproduction of ω and η mesons off carbon and niobium nuclei has been measured as a function of the meson momentum for incident photon energies of 1.2-2.9GeV at the electron accelerator ELSA. The mesons have been identified via the ω → π0 γ → 3 γ and η → π0η → 6 γ decays, respectively, registered with the CBELSA/TAPS detector system. From the measured meson momentum distributions the momentum dependence of the transparency ratio has been determined for both mesons. Within a Glauber analysis the in-medium ω and η widths and the corresponding absorption cross sections have been deduced as a function of the meson momentum. The results are compared to recent theoretical predictions for the in-medium ω width and η-N absorption cross sections. The energy dependence of the imaginary part of the ω- and η-nucleus optical potential has been extracted. The finer binning of the present data compared to the existing data allows a more reliable extrapolation towards the production threshold. The modulus of the imaginary part of the η-nucleus potential is found to be about three times smaller than recently determined values of the real part of the η-nucleus potential, which makes the η meson a suitable candidate for the search for meson-nucleus bound states. For the ω meson, the modulus of the imaginary part near threshold is comparable to the modulus of the real part of the potential. As a consequence, only broad structures can be expected, which makes the observation of ω mesic states very difficult experimentally.

Published
2016

26. Determination of the real part of the η′ -Nb optical potential

Author

Nanova, M., Friedrich, S., Metag, V., Paryev, E. Ya, Afzal, F. N., Bayadilov, D., Beck, R., Becker, M., Böse, S., Brinkmann, K. T., Crede, V., Elsner, D., Frommberger, F., Grüner, M., Gutz, E., Hammann, Ch, Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, P., Honisch, Ch, Jude, T., Kalischewski, F., Keshelashvili, I., Klein, F., Koop, K., Krusche, B., Makonyi, K., Messi, F., Müller, J., Müllers, J., Piontek, D. M., Rostomyan, T., Schaab, D., Schmidt, C., Schmieden, H., Schmitz, R., Seifen, T., Sowa, C., Spieker, K., Thiel, A., Thoma, U., Triffterer, T., Urban, M., Van Pee, H., Walther, D., Wendel, C., Wiedner, U., Witthauer, L., and Werthmüller, Dominik

Subjects
Nuclear Theory, High Energy Physics::Experiment, Nuclear Experiment
Abstract

The excitation function and momentum distribution of η′ mesons have been measured in photoproduction off Nb93 in the energy range of 1.2-2.9 GeV. The experiment has been performed with the combined Crystal Barrel and MiniTAPS detector system, using tagged photon beams from the ELSA electron accelerator. Information on the sign and magnitude of the real part of the η′-Nb potential has been extracted from a comparison of the data with model calculations. An attractive potential of -(41±10(stat)±15(syst)) MeV depth at normal nuclear matter density is deduced within model uncertainties. This value is consistent with the potential depth of -(37±10(stat)±10(syst)) MeV obtained in an earlier measurement for a light nucleus (carbon). This relatively shallow η′-nucleus potential will make the search for η′-nucleus bound states more difficult.

Published
2016

27. Determination of the real part of the ��'-Nb optical potential

Author

Nanova, M., Friedrich, S., Metag, V., Paryev, E. Ya., Afzal, F. N., Bayadilov, D., Beck, R., Becker, M., B��se, S., Brinkmann, K. -T., Crede, V., Elsner, D., Frommberger, F., Grtuner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, P., Honisch, Ch., Jude, T., Kalischewski, F., Keshelashvili, I., Klein, F., Koop, K., Krusche, B., Lang, M., Makonyi, K., Messi, F., M��ller, J., M��llers, J., Piontek, D. M., Rostomyan, T., Schaab, D., Schmidt, C., Schmieden, H., Schmitz, R., Seifen, T., Sowa, C., Spieker, K., Thiel, A., Thoma, U., Tristerer, T., Urban, M., van Pee, H., Walther, D., Wendel, C., Werthm��ller, D., Wiedner, U., Wilson, A., Witthauer, L., Wunderlich, Y., and Zaunick, H. -G.

Subjects
Nuclear Theory, FOS: Physical sciences, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

The excitation function and momentum distribution of ��' mesons have been measured in photoproduction off 93^Nb in the energy range of 1.2-2.9 GeV. The experiment has been performed with the combined Crystal Barrel and MiniTAPS detector system, using tagged photon beams from the ELSA electron accelerator. Information on the sign and magnitude of the real part of the ��'-Nb potential has been extracted from a comparison of the data with model calculations. An attractive potential of -(41 \pm 10(stat) \pm 15(syst)) MeV depth at normal nuclear matter density is deduced within model uncertainties. This value is consistent with the potential depth of -(37 \pm 10(stat) \pm 10(syst)) MeV obtained in an earlier measurement for a light nucleus (carbon). This relatively shallow ��'-nucleus potential will make the search for ��'-nucleus bound states more difficult., 9 pages, 6 figures

Published
2016
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28. The polarization observables T , P , and H and their impact on γp→pπ0 multipoles

Author

Hartmann, J., Dutz, H., Anisovich, A.V., Bayadilov, D., Beck, R., Becker, M., Beloglazov, Y., Berlin, A., Bichow, M., Böse, S., Brinkmann, K.-Th., Crede, V., Dieterle, M., Eberhardt, H., Elsner, D., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gottschall, M., Gridnev, A., Grüner, M., Goertz, St., Gutz, E., Hammann, Ch., Hannappel, J., Hannen, V., Herick, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jahn, O., Jude, T., Käser, A., Kaiser, D., Kalinowsky, H., Kalischewski, F., Klassen, P., Keshelashvili, I., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Makonyi, K., Messi, F., Metag, V., Meyer, W., Müller, J., Nanova, M., Nikonov, V., Novinski, D., Novotny, R., Piontek, D., Reeve, S., Rosenbaum, Ch., Roth, B., Reicherz, G., Rostomyan, T., Runkel, St., Sarantsev, A., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Thämer, Ph., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Winnebeck, A., and Witthauer, L.

Subjects
Polarization observables, Baryon spectroscopy, Nuclear Theory, Nuclear Experiment, Multipoles, Meson photoproduction, lcsh:Physics, lcsh:QC1-999
Abstract

Data on the polarization observables T , P , and H for the reaction γp→pπ0 are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction.

Published
2015

29. The polarization observables T, P, and H and their impact on $��p \to p��^0$ multipoles

Author

Hartmann, J., Dutz, H., Anisovich, A. V., Bayadilov, D., Beck, R., Becker, M., Beloglazov, Y., Berlin, A., Bichow, M., B��se, S., Brinkmann, K. -Th., Crede, V., Dieterle, M., Eberhardt, H., Elsner, D., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gottschall, M., Gridnev, A., Gr��ner, M., G��rtz, St., Gutz, E., Hammann, Ch., Hannappel, J., Hannen, V., Herick, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jahn, O., Jude, T., K��ser, A., Kaiser, D., Kalinowsky, H., Kalischewski, F., Klassen, P., Keshelashvili, I., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Makonyi, K., Messi, F., Metag, V., Meyer, W., M��ller, J., Nanova, M., Nikonov, V., Novinski, D., Novotny, R., Piontek, D., Reeve, S., Rosenbaum, Ch., Roth, B., Reicherz, G., Rostomyan, T., Runkel, St., Sarantsev, A., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Th��mer, Ph., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Winnebeck, A., and Witthauer, L.

Subjects
Nuclear Theory, FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

Data on the polarization observables T, P, and H for the reaction $��p\to p��^0$ are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction.

Published
2015
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30. Determination of the ��'-nucleus optical potential

Author

Nanova, M., Metag, V., Paryev, E. Ya., Bayadilov, D., Bantes, B., Beck, R., Beloglazov, Y. A., B��se, S., Brinkmann, K. -T., Challand, Th., Crede, V., Dahlke, T., Dietz, F., Drexler, P., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, S., Frommberger, F., Funke, Ch., Gottschall, M., Gridnev, A., Gr��ner, M., Gutz, E., Hammann, Ch., Hammann, D., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, P., Honisch, Ch., Jaegle, I., Kaiser, D., Kalinowsky, H., Kammer, S., Keshelashvili, I., Kleber, V., Klein, F., Klempt, E., Krusche, B., Lang, M., Lopatin, I. V., Maghrbi, Y., Makonyi, K., M��ller, J., Odenthal, T., Piontek, D., Schaepe, S., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Thiel, A., Thoma, U., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., Winnebeck, A., and Zenke, F.

Subjects
Nuclear Theory, FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

The excitation function and momentum distribution of $��^\prime$ mesons have been measured in photon induced reactions on $^{12}{}$C in the energy range of 1250-2600 MeV. The experiment was performed with tagged photon beams from the ELSA electron accelerator using the Crystal Barrel and TAPS detectors. The data are compared to model calculations to extract information on the sign and magnitude of the real part of the $��^\prime$-nucleus potential. Within the model, the comparison indicates an attractive potential of -($37 \pm 10(stat)\pm10(syst)$) MeV depth at normal nuclear matter density. Since the modulus of this depth is larger than the modulus of the imaginary part of the $��^\prime$-nucleus potential of -($10\pm2.5$) MeV, determined by transparency ratio measurements, a search for resolved $��^\prime$-bound states appears promising., 13 pages, 6 figures

Published
2013
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31. First measurement of the helicity asymmetry for $��p\rightarrow p��^0$ in the resonance region

Author

Gottschall, M., Anisovich, A. V., Bantes, B., Bayadilov, D., Beck, R., Bichow, M., B��se, S., Brinkmann, K. -Th., Challand, Th., Crede, V., Dietz, F., Dutz, H., Eberhardt, H., Elsner, D., Ewald, R., Fornet-Ponse, K., Friedrich, St., Frommberger, F., Funke, Ch., Gridnev, A., Gr��ner, M., Gutz, E., Hammann, Ch., Hannappel, J., Hartmann, J., Hillert, W., Hoffmeister, Ph., Honisch, Ch., Jaegle, I., Kaiser, D., Kalinowsky, H., Kammer, S., Keshelashvili, I., Klein, F., Klempt, E., Koop, K., Krusche, B., Kube, M., Lang, M., Lopatin, I., Maghrbi, Y., Makonyi, K., Metag, V., Meyer, W., M��ller, J., Nanova, M., Nikonov, V., Novotny, R., Piontek, D., Reicherz, G., Rostomyan, T., Sarantsev, A., Schaepe, St., Schmidt, Ch., Schmieden, H., Schmitz, R., Seifen, T., Sokhoyan, V., Thiel, A., Thoma, U., Urban, M., van Pee, H., Walther, D., Wendel, Ch., Wiedner, U., Wilson, A., and Winnebeck, A.

Subjects
Nuclear Theory, FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

The first measurement of the helicity dependence of the photoproduction cross section of single neutral pions off protons is reported for photon energies from 600 to 2300\,MeV, covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, and BnGa partial wave analyses. Strikingly large differences between data and predictions are observed which are traced to differences in the helicity amplitudes of well known and established resonances. Precise values for the helicity amplitudes of several resonances are reported.

Published
2013
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32. Measurement of double polarisation asymmetries in ω -photoproduction

Author

Eberhardt, H., primary, Jude, T.C., additional, Schmieden, H., additional, Anisovich, A.V., additional, Bantes, B., additional, Bayadilov, D., additional, Beck, R., additional, Beloglazov, Yu., additional, Bichow, M., additional, Böse, S., additional, Brinkmann, K.-Th., additional, Challand, Th., additional, Crede, V., additional, Diez, F., additional, Drexler, P., additional, Dutz, H., additional, Elsner, D., additional, Ewald, R., additional, Fornet-Ponse, K., additional, Friedrich, St., additional, Frommberger, F., additional, Funke, Ch., additional, Gottschall, M., additional, Gridnev, A., additional, Grüner, M., additional, Gutz, E., additional, Hammann, Ch., additional, Hannappel, J., additional, Hartmann, J., additional, Hillert, W., additional, Hoffmeister, Ph., additional, Honisch, Ch., additional, Jaegle, I., additional, Kaiser, D., additional, Kalinowsky, H., additional, Kalischewski, F., additional, Kammer, S., additional, Keshelashvili, I., additional, Kleber, V., additional, Klein, F., additional, Klempt, E., additional, Koop, K., additional, Krusche, B., additional, Kube, M., additional, Lang, M., additional, Lopatin, I., additional, Maghrbi, Y., additional, Makonyi, K., additional, Metag, V., additional, Meyer, W., additional, Müller, J., additional, Nanova, M., additional, Nikonov, V., additional, Novotny, R., additional, Piontek, D., additional, Reeve, S., additional, Reicherz, G., additional, Rostomyan, T., additional, Runkel, S., additional, Sarantsev, A., additional, Schaepe, St., additional, Schmidt, Ch., additional, Schmitz, R., additional, Seifen, T., additional, Sokhoyan, V., additional, Sumachev, V., additional, Thiel, A., additional, Thoma, U., additional, Urban, M., additional, van Pee, H., additional, Walther, D., additional, Wendel, Ch., additional, Wiedner, U., additional, Wilson, A., additional, and Winnebeck, A., additional

Published
2015
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33. The polarization observables T , P , and H and their impact onγp→pπ0multipoles

Author

Hartmann, J., primary, Dutz, H., additional, Anisovich, A.V., additional, Bayadilov, D., additional, Beck, R., additional, Becker, M., additional, Beloglazov, Y., additional, Berlin, A., additional, Bichow, M., additional, Böse, S., additional, Brinkmann, K.-Th., additional, Crede, V., additional, Dieterle, M., additional, Eberhardt, H., additional, Elsner, D., additional, Fornet-Ponse, K., additional, Friedrich, St., additional, Frommberger, F., additional, Funke, Ch., additional, Gottschall, M., additional, Gridnev, A., additional, Grüner, M., additional, Goertz, St., additional, Gutz, E., additional, Hammann, Ch., additional, Hannappel, J., additional, Hannen, V., additional, Herick, J., additional, Hillert, W., additional, Hoffmeister, Ph., additional, Honisch, Ch., additional, Jahn, O., additional, Jude, T., additional, Käser, A., additional, Kaiser, D., additional, Kalinowsky, H., additional, Kalischewski, F., additional, Klassen, P., additional, Keshelashvili, I., additional, Klein, F., additional, Klempt, E., additional, Koop, K., additional, Krusche, B., additional, Kube, M., additional, Lang, M., additional, Lopatin, I., additional, Makonyi, K., additional, Messi, F., additional, Metag, V., additional, Meyer, W., additional, Müller, J., additional, Nanova, M., additional, Nikonov, V., additional, Novinski, D., additional, Novotny, R., additional, Piontek, D., additional, Reeve, S., additional, Rosenbaum, Ch., additional, Roth, B., additional, Reicherz, G., additional, Rostomyan, T., additional, Runkel, St., additional, Sarantsev, A., additional, Schmidt, Ch., additional, Schmieden, H., additional, Schmitz, R., additional, Seifen, T., additional, Sokhoyan, V., additional, Thämer, Ph., additional, Thiel, A., additional, Thoma, U., additional, Urban, M., additional, van Pee, H., additional, Walther, D., additional, Wendel, Ch., additional, Wiedner, U., additional, Wilson, A., additional, Winnebeck, A., additional, and Witthauer, L., additional

Published
2015
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34. Experimental constraints on the ω –nucleus real potential

Author

Friedrich, S., primary, Makonyi, K., additional, Metag, V., additional, Bayadilov, D., additional, Bantes, B., additional, Beck, R., additional, Beloglazov, Y.A., additional, Böse, S., additional, Brinkmann, K.-T., additional, Challand, Th., additional, Crede, V., additional, Dahlke, T., additional, Dietz, F., additional, Drexler, P., additional, Eberhardt, H., additional, Elsner, D., additional, Ewald, R., additional, Fornet-Ponse, K., additional, Frommberger, F., additional, Funke, Ch., additional, Gottschall, M., additional, Gridnev, A., additional, Grüner, M., additional, Gutz, E., additional, Hammann, Ch., additional, Hammann, D., additional, Hannappel, J., additional, Hartmann, J., additional, Hillert, W., additional, Hirenzaki, S., additional, Hoffmeister, P., additional, Honisch, Ch., additional, Jaegle, I., additional, Kaiser, D., additional, Kalinowsky, H., additional, Kammer, S., additional, Keshelashvili, I., additional, Kleber, V., additional, Klein, F., additional, Krusche, B., additional, Lang, M., additional, Lopatin, I.V., additional, Maghrbi, Y., additional, Nanova, M., additional, Nagahiro, H., additional, Müller, J., additional, Odenthal, T., additional, Piontek, D., additional, Rostomyan, T., additional, Schaepe, S., additional, Schmidt, Ch., additional, Schmieden, H., additional, Schmitz, R., additional, Seifen, T., additional, Thiel, A., additional, Thoma, U., additional, van Pee, H., additional, Walther, D., additional, Weil, J., additional, Wendel, Ch., additional, Wiedner, U., additional, Wilson, A., additional, Winnebeck, A., additional, and Zenke, F., additional

Published
2014
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35. First Measurement of the Helicity Asymmetry forγp→pπ0in the Resonance Region

Author

Gottschall, M., primary, Anisovich, A. V., additional, Bantes, B., additional, Bayadilov, D., additional, Beck, R., additional, Bichow, M., additional, Böse, S., additional, Brinkmann, K.-Th., additional, Challand, Th., additional, Crede, V., additional, Dietz, F., additional, Dutz, H., additional, Eberhardt, H., additional, Elsner, D., additional, Ewald, R., additional, Fornet-Ponse, K., additional, Friedrich, St., additional, Frommberger, F., additional, Funke, Ch., additional, Gridnev, A., additional, Grüner, M., additional, Gutz, E., additional, Hammann, Ch., additional, Hannappel, J., additional, Hartmann, J., additional, Hillert, W., additional, Hoffmeister, Ph., additional, Honisch, Ch., additional, Jaegle, I., additional, Kaiser, D., additional, Kalinowsky, H., additional, Kammer, S., additional, Keshelashvili, I., additional, Klein, F., additional, Klempt, E., additional, Koop, K., additional, Krusche, B., additional, Kube, M., additional, Lang, M., additional, Lopatin, I., additional, Maghrbi, Y., additional, Makonyi, K., additional, Metag, V., additional, Meyer, W., additional, Müller, J., additional, Nanova, M., additional, Nikonov, V., additional, Novotny, R., additional, Piontek, D., additional, Reicherz, G., additional, Rostomyan, T., additional, Sarantsev, A., additional, Schaepe, St., additional, Schmidt, Ch., additional, Schmieden, H., additional, Schmitz, R., additional, Seifen, T., additional, Sokhoyan, V., additional, Thiel, A., additional, Thoma, U., additional, Urban, M., additional, van Pee, H., additional, Walther, D., additional, Wendel, Ch., additional, Wiedner, U., additional, Wilson, A., additional, and Winnebeck, A., additional

Published
2014
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36. Determination of the η′-nucleus optical potential

Author

Nanova, M., primary, Metag, V., additional, Paryev, E.Ya., additional, Bayadilov, D., additional, Bantes, B., additional, Beck, R., additional, Beloglazov, Y.A., additional, Böse, S., additional, Brinkmann, K.-T., additional, Challand, Th., additional, Crede, V., additional, Dahlke, T., additional, Dietz, F., additional, Drexler, P., additional, Eberhardt, H., additional, Elsner, D., additional, Ewald, R., additional, Fornet-Ponse, K., additional, Friedrich, S., additional, Frommberger, F., additional, Funke, Ch., additional, Gottschall, M., additional, Gridnev, A., additional, Grüner, M., additional, Gutz, E., additional, Hammann, Ch., additional, Hammann, D., additional, Hannappel, J., additional, Hartmann, J., additional, Hillert, W., additional, Hoffmeister, P., additional, Honisch, Ch., additional, Jaegle, I., additional, Kaiser, D., additional, Kalinowsky, H., additional, Kammer, S., additional, Keshelashvili, I., additional, Kleber, V., additional, Klein, F., additional, Klempt, E., additional, Krusche, B., additional, Lang, M., additional, Lopatin, I.V., additional, Maghrbi, Y., additional, Makonyi, K., additional, Müller, J., additional, Odenthal, T., additional, Piontek, D., additional, Schaepe, S., additional, Schmidt, Ch., additional, Schmieden, H., additional, Schmitz, R., additional, Seifen, T., additional, Thiel, A., additional, Thoma, U., additional, van Pee, H., additional, Walther, D., additional, Wendel, Ch., additional, Wiedner, U., additional, Wilson, A., additional, Winnebeck, A., additional, and Zenke, F., additional

Published
2013
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39. Thielet al.Reply

Author

Thiel, A., primary, Anisovich, A. V., additional, Bayadilov, D., additional, Bantes, B., additional, Beck, R., additional, Beloglazov, Yu., additional, Bichow, M., additional, Böse, S., additional, Brinkmann, K.-Th., additional, Challand, Th., additional, Crede, V., additional, Dietz, F., additional, Drexler, P., additional, Dutz, H., additional, Eberhardt, H., additional, Elsner, D., additional, Ewald, R., additional, Fornet-Ponse, K., additional, Friedrich, St., additional, Frommberger, F., additional, Funke, Ch., additional, Gottschall, M., additional, Grüner, M., additional, Gutz, E., additional, Hammann, Ch., additional, Hannappel, J., additional, Hartmann, J., additional, Hillert, W., additional, Hoffmeister, Ph., additional, Honisch, Ch., additional, Jaegle, I., additional, Jürgensen, I., additional, Kaiser, D., additional, Kalinowsky, H., additional, Kalischewski, F., additional, Kammer, S., additional, Keshelashvili, I., additional, Kleber, V., additional, Klein, F., additional, Klempt, E., additional, Krusche, B., additional, Lang, M., additional, Lopatin, I., additional, Maghrbi, Y., additional, Makonyi, K., additional, Metag, V., additional, Meyer, W., additional, Müller, J., additional, Nanova, M., additional, Nikonov, V., additional, Novotny, R., additional, Piontek, D., additional, Reicherz, G., additional, Sarantsev, A., additional, Schmidt, Ch., additional, Schmieden, H., additional, Seifen, T., additional, Sokhoyan, V., additional, Sumachev, V., additional, Thoma, U., additional, vanPee, H., additional, Walther, D., additional, Wendel, Ch., additional, Wiedner, U., additional, Wilson, A., additional, Winnebeck, A., additional, and Wunderlich, Y., additional

Published
2013
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41. Well-Established Nucleon Resonances Revisited by Double-Polarization Measurements

Author

Thiel, A., primary, Anisovich, A. V., additional, Bayadilov, D., additional, Bantes, B., additional, Beck, R., additional, Beloglazov, Yu., additional, Bichow, M., additional, Böse, S., additional, Brinkmann, K.-Th., additional, Challand, Th., additional, Crede, V., additional, Dietz, F., additional, Drexler, P., additional, Dutz, H., additional, Eberhardt, H., additional, Elsner, D., additional, Ewald, R., additional, Fornet-Ponse, K., additional, Friedrich, St., additional, Frommberger, F., additional, Funke, Ch., additional, Gottschall, M., additional, Grüner, M., additional, Gutz, E., additional, Hammann, Ch., additional, Hannappel, J., additional, Hartmann, J., additional, Hillert, W., additional, Hoffmeister, Ph., additional, Honisch, Ch., additional, Jaegle, I., additional, Jürgensen, I., additional, Kaiser, D., additional, Kalinowsky, H., additional, Kalischewski, F., additional, Kammer, S., additional, Keshelashvili, I., additional, Kleber, V., additional, Klein, F., additional, Klempt, E., additional, Krusche, B., additional, Lang, M., additional, Lopatin, I., additional, Maghrbi, Y., additional, Makonyi, K., additional, Metag, V., additional, Meyer, W., additional, Müller, J., additional, Nanova, M., additional, Nikonov, V., additional, Novotny, R., additional, Piontek, D., additional, Reicherz, G., additional, Sarantsev, A., additional, Schmidt, Ch., additional, Schmieden, H., additional, Seifen, T., additional, Sokhoyan, V., additional, Sumachev, V., additional, Thoma, U., additional, vanPee, H., additional, Walther, D., additional, Wendel, Ch., additional, Wiedner, U., additional, Wilson, A., additional, Winnebeck, A., additional, and Wunderlich, Y., additional

Published
2012
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42. First measurement of the helicity asymmetry for γp → pπ0 in the resonance region.

Author

Gottschall M, Anisovich AV, Bantes B, Bayadilov D, Beck R, Bichow M, Böse S, Brinkmann KT, Challand T, Crede V, Dietz F, Dutz H, Eberhardt H, Elsner D, Ewald R, Fornet-Ponse K, Friedrich S, Frommberger F, Funke Ch, Gridnev A, Grüner M, Gutz E, Hammann Ch, Hannappel J, Hartmann J, Hillert W, Hoffmeister P, Honisch Ch, Jaegle I, Kaiser D, Kalinowsky H, Kammer S, Keshelashvili I, Klein F, Klempt E, Koop K, Krusche B, Kube M, Lang M, Lopatin I, Maghrbi Y, Makonyi K, Metag V, Meyer W, Müller J, Nanova M, Nikonov V, Novotny R, Piontek D, Reicherz G, Rostomyan T, Sarantsev A, Schaepe S, Schmidt Ch, Schmieden H, Schmitz R, Seifen T, Sokhoyan V, Thiel A, Thoma U, Urban M, van Pee H, Walther D, Wendel Ch, Wiedner U, Wilson A, and Winnebeck A

Abstract

The first measurement of the helicity dependence of the photoproduction cross section of single neutral pions off protons is reported for photon energies from 600 to 2300 MeV, covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, and BnGa partial wave analyses. Strikingly large differences between data and predictions are observed, which are traced to differences in the helicity amplitudes of well-known and established resonances. Precise values for the helicity amplitudes of several resonances are reported.

Published
2014
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43. Thiel et al. reply:.

Author

Thiel A, Anisovich AV, Bayadilov D, Bantes B, Beck R, Beloglazov Y, Bichow M, Böse S, Brinkmann KT, Challand T, Crede V, Dietz F, Drexler P, Dutz H, Eberhardt H, Elsner D, Ewald R, Fornet-Ponse K, Friedrich S, Frommberger F, Funke Ch, Gottschall M, Grüner M, Gutz E, Hammann Ch, Hannappel J, Hartmann J, Hillert W, Hoffmeister P, Honisch Ch, Jaegle I, Jürgensen I, Kaiser D, Kalinowsky H, Kalischewski F, Kammer S, Keshelashvili I, Kleber V, Klein F, Klempt E, Krusche B, Lang M, Lopatin I, Maghrbi Y, Makonyi K, Metag V, Meyer W, Müller J, Nanova M, Nikonov V, Novotny R, Piontek D, Reicherz G, Sarantsev A, Schmidt Ch, Schmieden H, Seifen T, Sokhoyan V, Sumachev V, Thoma U, vanPee H, Walther D, Wendel Ch, Wiedner U, Wilson A, Winnebeck A, and Wunderlich Y

Published
2013
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