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Title: Photoproduction of π 0 mesons off protons and neutrons in the second and third nucleon resonance regions

Abstract

Background: Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the elec- tromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets. Purpose: Study experimentally single π0 photoproduction off quasi-free nucleons from the deuteron. Investigate nuclear effects by a comparison of the results for free protons and quasi-free protons. Use the quasi-free neutron data (corrected for nuclear effects) to test the predictions of reaction models and partial wave analysis (PWA) for γn → nπ 0 derived from the analysis of the other isospin channels. Methods: High statistics angular distributions and total cross sections for the photoproduction of π 0 mesons off the deuteron with coincident detection of recoil nucleons have been measured for the first time. The experiment was performed at the tagged photon beam of the Mainz Microtron (MAMI) accelerator for photon energies between 0.45 GeV and 1.4 GeV, using an almost 4π electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. A complete kinematic reconstruction of the final state removed the effects of Fermi motion. Results: Significant effects from final state interactions (FSI)more » were observed for participant protons in comparison to free proton targets (between 30% and almost 40%). The data in coincidence with recoil neutrons were corrected for such effects under the assumption that they are identical for participant protons and neutrons. Reaction model predictions and PWA for γn → nπ 0, based on fits to data for the other isospin channels, disagreed between themselves and no model provided a good description of the new data. Conclusions: The results demonstrate clearly the importance of a measurement of the fully neutral final state for the isospin decomposition of the cross section. Model refits, for example from the Bonn-Gatchina analysis, show that the new and the previous data for the other three isospin channels can be simultaneously described when the contributions of several partial waves are modified. Finally, the results are also relevant for the suppression of the higher resonance bumps in total photoabsorption on nuclei, which are not well understood.« less

Authors:
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Publication Date:
Research Org.:
Kent State Univ., Kent, OH (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Org.:
A2 Collaboration
OSTI Identifier:
1456240
Alternate Identifier(s):
OSTI ID: 1456273
Grant/Contract Number:
FG02-01ER41194; FG02-99ER41110; FG02-88ER40415; PHY-1039130; IIA-1358175
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review C
Additional Journal Information:
Journal Volume: 97; Journal Issue: 6; Journal ID: ISSN 2469-9985
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Pion Photoproduction, Final-State Interactions

Citation Formats

Dieterle, M., Werthmüller, D., Abt, S., Afzal, F., Aguar Bartolome, P., Ahmed, Z., Ahrens, J., Annand, J. R. M., Arends, H. J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N., Braghieri, A., Briscoe, W. J., Cherepnya, S., Cividini, F., Collicott, C., Costanza, S., Denig, A., Downie, E. J., Drexler, P., Fil'kov, L. V., Garni, S., 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., 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., Metag, V., Middleton, D. G., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Neganov, A., Neiser, A., Oberle, M., Ostrick, M., Otte, P. B., Oussena, B., Paudyal, D., Pedroni, P., Polonski, A., Prakhov, S. N., 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., Wettig, J., Witthauer, L., Wolfes, M., and Zana, L. A. Photoproduction of π0 mesons off protons and neutrons in the second and third nucleon resonance regions. United States: N. p., 2018. Web. doi:10.1103/PhysRevC.97.065205.
Dieterle, M., Werthmüller, D., Abt, S., Afzal, F., Aguar Bartolome, P., Ahmed, Z., Ahrens, J., Annand, J. R. M., Arends, H. J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N., Braghieri, A., Briscoe, W. J., Cherepnya, S., Cividini, F., Collicott, C., Costanza, S., Denig, A., Downie, E. J., Drexler, P., Fil'kov, L. V., Garni, S., 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., 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., Metag, V., Middleton, D. G., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Neganov, A., Neiser, A., Oberle, M., Ostrick, M., Otte, P. B., Oussena, B., Paudyal, D., Pedroni, P., Polonski, A., Prakhov, S. N., 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., Wettig, J., Witthauer, L., Wolfes, M., & Zana, L. A. Photoproduction of π0 mesons off protons and neutrons in the second and third nucleon resonance regions. United States. doi:10.1103/PhysRevC.97.065205.
Dieterle, M., Werthmüller, D., Abt, S., Afzal, F., Aguar Bartolome, P., Ahmed, Z., Ahrens, J., Annand, J. R. M., Arends, H. J., Bashkanov, M., Beck, R., Biroth, M., Borisov, N., Braghieri, A., Briscoe, W. J., Cherepnya, S., Cividini, F., Collicott, C., Costanza, S., Denig, A., Downie, E. J., Drexler, P., Fil'kov, L. V., Garni, S., 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., 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., Metag, V., Middleton, D. G., Miskimen, R., Mornacchi, E., Mushkarenkov, A., Neganov, A., Neiser, A., Oberle, M., Ostrick, M., Otte, P. B., Oussena, B., Paudyal, D., Pedroni, P., Polonski, A., Prakhov, S. N., 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., Wettig, J., Witthauer, L., Wolfes, M., and Zana, L. A. Thu . "Photoproduction of π0 mesons off protons and neutrons in the second and third nucleon resonance regions". United States. doi:10.1103/PhysRevC.97.065205.
@article{osti_1456240,
title = {Photoproduction of π0 mesons off protons and neutrons in the second and third nucleon resonance regions},
author = {Dieterle, M. and Werthmüller, D. and Abt, S. and Afzal, F. and Aguar Bartolome, P. and Ahmed, Z. and Ahrens, J. and Annand, J. R. M. and Arends, H. J. and Bashkanov, M. and Beck, R. and Biroth, M. and Borisov, N. and Braghieri, A. and Briscoe, W. J. and Cherepnya, S. and Cividini, F. and Collicott, C. and Costanza, S. and Denig, A. and Downie, E. J. and Drexler, P. and Fil'kov, L. V. and Garni, S. and Glazier, D. I. and Gorodnov, I. and Gradl, W. and Günther, M. and Gurevich, D. and Heijkenskjöld, L. and Hornidge, D. and Huber, G. M. and Käser, A. and Kashevarov, V. L. and Kay, S. and Keshelashvili, I. and Kondratiev, R. and Korolija, M. and Krusche, B. and Lazarev, A. and Lisin, V. and Livingston, K. and Lutterer, S. and MacGregor, I. J. D. and Manley, D. M. and Martel, P. P. and McGeorge, J. C. and Metag, V. and Middleton, D. G. and Miskimen, R. and Mornacchi, E. and Mushkarenkov, A. and Neganov, A. and Neiser, A. and Oberle, M. and Ostrick, M. and Otte, P. B. and Oussena, B. and Paudyal, D. and Pedroni, P. and Polonski, A. and Prakhov, S. N. and Ron, G. and Rostomyan, T. and Sarty, A. and Sfienti, C. and Sokhoyan, V. and Spieker, K. and Steffen, O. and Strakovsky, I. I. and Strub, T. and Supek, I. and Thiel, A. and Thiel, M. and Thomas, A. and Unverzagt, M. and Usov, Yu. A. and Wagner, S. and Walford, N. K. and Watts, D. P. and Wettig, J. and Witthauer, L. and Wolfes, M. and Zana, L. A.},
abstractNote = {Background: Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the elec- tromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets. Purpose: Study experimentally single π0 photoproduction off quasi-free nucleons from the deuteron. Investigate nuclear effects by a comparison of the results for free protons and quasi-free protons. Use the quasi-free neutron data (corrected for nuclear effects) to test the predictions of reaction models and partial wave analysis (PWA) for γn → nπ0 derived from the analysis of the other isospin channels. Methods: High statistics angular distributions and total cross sections for the photoproduction of π0 mesons off the deuteron with coincident detection of recoil nucleons have been measured for the first time. The experiment was performed at the tagged photon beam of the Mainz Microtron (MAMI) accelerator for photon energies between 0.45 GeV and 1.4 GeV, using an almost 4π electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. A complete kinematic reconstruction of the final state removed the effects of Fermi motion. Results: Significant effects from final state interactions (FSI) were observed for participant protons in comparison to free proton targets (between 30% and almost 40%). The data in coincidence with recoil neutrons were corrected for such effects under the assumption that they are identical for participant protons and neutrons. Reaction model predictions and PWA for γn → nπ0, based on fits to data for the other isospin channels, disagreed between themselves and no model provided a good description of the new data. Conclusions: The results demonstrate clearly the importance of a measurement of the fully neutral final state for the isospin decomposition of the cross section. Model refits, for example from the Bonn-Gatchina analysis, show that the new and the previous data for the other three isospin channels can be simultaneously described when the contributions of several partial waves are modified. Finally, the results are also relevant for the suppression of the higher resonance bumps in total photoabsorption on nuclei, which are not well understood.},
doi = {10.1103/PhysRevC.97.065205},
journal = {Physical Review C},
number = 6,
volume = 97,
place = {United States},
year = {Thu Jun 21 00:00:00 EDT 2018},
month = {Thu Jun 21 00:00:00 EDT 2018}
}

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