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Title: Photoproduction of $$ \pi^{0}$$-pairs off protons and off neutrons

Abstract

Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of π 0π 0 pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557MeV, which produced bremsstrahlung in thin radiator foils. The tagged photon beam covered energies up to 1400MeV. The data from the free proton target are in good agreement with previous measurements and were only used to test the analysis procedures. The results for differential cross sections (angular distributions and invariant-mass distributions) for free and quasi-free protons are almost identical in shape, but differ in absolute magnitude up to 15%. Thus, moderate final-state interaction effects are present. The data for quasi-free neutrons are similar to the proton data in the second resonance region (final-state invariant masses up to ≈1550 MeV), where both reactions are dominated by the N(1520)3/2 →Δ(1232)3/2 +π decay. At higher energies, angular and invariant-mass distributions are different. A simple analysis of the shapes of the invariant-mass distributions in the third resonance region is consistent with strong contributions of anmore » N*→Nσ decay for the proton, while the reaction is dominated by a sequential decay via a Δπ intermediate state for the neutron. Here, the data are compared to predictions from the Two-Pion-MAID model and the Bonn-Gatchina coupled-channel analysis.« less

Authors:
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Publication Date:
Research Org.:
Univ. of Massachusetts, Amherst, MA (United States)
Sponsoring Org.:
USDOE
Contributing Org.:
The A2 Collaboration
OSTI Identifier:
1437123
Grant/Contract Number:  
FG02-88ER40415
Resource Type:
Accepted Manuscript
Journal Name:
European Physical Journal. A
Additional Journal Information:
Journal Volume: 51; Journal Issue: 11; Journal ID: ISSN 1434-6001
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS

Citation Formats

Dieterle, M., Oberle, M., Ahrens, J., Annand, J. R. M., Arends, H. J., Bantawa, K., Bartolome, P. A., Beck, R., Bekrenev, V., Berghäuser, H., Braghieri, A., Branford, D., Briscoe, W. J., Brudvik, J., Cherepnya, S., Costanza, S., Demissie, B., Downie, E. J., Drexler, P., Fil’kov, L. V., Fix, A., Garni, S., Glazier, D. I., Hamilton, D., Heid, E., Hornidge, D., Howdle, D., Huber, G. M., Jahn, O., Jude, T. C., Käser, A., Kashevarov, V. L., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lisin, V., Livingston, K., MacGregor, I. J. D., Maghrbi, Y., Mancell, J., Manley, D. M., Marinides, Z., McGeorge, J. C., McNicoll, E., Mekterovic, D., Metag, V., Micanovic, S., Middleton, D. G., Mushkarenkov, A., Nikolaev, A., Novotny, R., Ostrick, M., Otte, P., Oussena, B., Pedroni, P., Pheron, F., Polonski, A., Prakhov, S., Robinson, J., Rostomyan, T., Schumann, S., Sikora, M. H., Sober, D. I., Starostin, A., Strub, Th., Supek, I., Thiel, M., Thomas, A., Unverzagt, M., Walford, N. K., Watts, D. P., Werthmüller, D., and Witthauer, L. Photoproduction of $ \pi^{0}$-pairs off protons and off neutrons. United States: N. p., 2015. Web. doi:10.1140/epja/i2015-15142-8.
Dieterle, M., Oberle, M., Ahrens, J., Annand, J. R. M., Arends, H. J., Bantawa, K., Bartolome, P. A., Beck, R., Bekrenev, V., Berghäuser, H., Braghieri, A., Branford, D., Briscoe, W. J., Brudvik, J., Cherepnya, S., Costanza, S., Demissie, B., Downie, E. J., Drexler, P., Fil’kov, L. V., Fix, A., Garni, S., Glazier, D. I., Hamilton, D., Heid, E., Hornidge, D., Howdle, D., Huber, G. M., Jahn, O., Jude, T. C., Käser, A., Kashevarov, V. L., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lisin, V., Livingston, K., MacGregor, I. J. D., Maghrbi, Y., Mancell, J., Manley, D. M., Marinides, Z., McGeorge, J. C., McNicoll, E., Mekterovic, D., Metag, V., Micanovic, S., Middleton, D. G., Mushkarenkov, A., Nikolaev, A., Novotny, R., Ostrick, M., Otte, P., Oussena, B., Pedroni, P., Pheron, F., Polonski, A., Prakhov, S., Robinson, J., Rostomyan, T., Schumann, S., Sikora, M. H., Sober, D. I., Starostin, A., Strub, Th., Supek, I., Thiel, M., Thomas, A., Unverzagt, M., Walford, N. K., Watts, D. P., Werthmüller, D., & Witthauer, L. Photoproduction of $ \pi^{0}$-pairs off protons and off neutrons. United States. doi:10.1140/epja/i2015-15142-8.
Dieterle, M., Oberle, M., Ahrens, J., Annand, J. R. M., Arends, H. J., Bantawa, K., Bartolome, P. A., Beck, R., Bekrenev, V., Berghäuser, H., Braghieri, A., Branford, D., Briscoe, W. J., Brudvik, J., Cherepnya, S., Costanza, S., Demissie, B., Downie, E. J., Drexler, P., Fil’kov, L. V., Fix, A., Garni, S., Glazier, D. I., Hamilton, D., Heid, E., Hornidge, D., Howdle, D., Huber, G. M., Jahn, O., Jude, T. C., Käser, A., Kashevarov, V. L., Keshelashvili, I., Kondratiev, R., Korolija, M., Krusche, B., Lisin, V., Livingston, K., MacGregor, I. J. D., Maghrbi, Y., Mancell, J., Manley, D. M., Marinides, Z., McGeorge, J. C., McNicoll, E., Mekterovic, D., Metag, V., Micanovic, S., Middleton, D. G., Mushkarenkov, A., Nikolaev, A., Novotny, R., Ostrick, M., Otte, P., Oussena, B., Pedroni, P., Pheron, F., Polonski, A., Prakhov, S., Robinson, J., Rostomyan, T., Schumann, S., Sikora, M. H., Sober, D. I., Starostin, A., Strub, Th., Supek, I., Thiel, M., Thomas, A., Unverzagt, M., Walford, N. K., Watts, D. P., Werthmüller, D., and Witthauer, L. Wed . "Photoproduction of $ \pi^{0}$-pairs off protons and off neutrons". United States. doi:10.1140/epja/i2015-15142-8. https://www.osti.gov/servlets/purl/1437123.
@article{osti_1437123,
title = {Photoproduction of $ \pi^{0}$-pairs off protons and off neutrons},
author = {Dieterle, M. and Oberle, M. and Ahrens, J. and Annand, J. R. M. and Arends, H. J. and Bantawa, K. and Bartolome, P. A. and Beck, R. and Bekrenev, V. and Berghäuser, H. and Braghieri, A. and Branford, D. and Briscoe, W. J. and Brudvik, J. and Cherepnya, S. and Costanza, S. and Demissie, B. and Downie, E. J. and Drexler, P. and Fil’kov, L. V. and Fix, A. and Garni, S. and Glazier, D. I. and Hamilton, D. and Heid, E. and Hornidge, D. and Howdle, D. and Huber, G. M. and Jahn, O. and Jude, T. C. and Käser, A. and Kashevarov, V. L. and Keshelashvili, I. and Kondratiev, R. and Korolija, M. and Krusche, B. and Lisin, V. and Livingston, K. and MacGregor, I. J. D. and Maghrbi, Y. and Mancell, J. and Manley, D. M. and Marinides, Z. and McGeorge, J. C. and McNicoll, E. and Mekterovic, D. and Metag, V. and Micanovic, S. and Middleton, D. G. and Mushkarenkov, A. and Nikolaev, A. and Novotny, R. and Ostrick, M. and Otte, P. and Oussena, B. and Pedroni, P. and Pheron, F. and Polonski, A. and Prakhov, S. and Robinson, J. and Rostomyan, T. and Schumann, S. and Sikora, M. H. and Sober, D. I. and Starostin, A. and Strub, Th. and Supek, I. and Thiel, M. and Thomas, A. and Unverzagt, M. and Walford, N. K. and Watts, D. P. and Werthmüller, D. and Witthauer, L.},
abstractNote = {Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of π0π0 pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557MeV, which produced bremsstrahlung in thin radiator foils. The tagged photon beam covered energies up to 1400MeV. The data from the free proton target are in good agreement with previous measurements and were only used to test the analysis procedures. The results for differential cross sections (angular distributions and invariant-mass distributions) for free and quasi-free protons are almost identical in shape, but differ in absolute magnitude up to 15%. Thus, moderate final-state interaction effects are present. The data for quasi-free neutrons are similar to the proton data in the second resonance region (final-state invariant masses up to ≈1550 MeV), where both reactions are dominated by the N(1520)3/2–→Δ(1232)3/2+π decay. At higher energies, angular and invariant-mass distributions are different. A simple analysis of the shapes of the invariant-mass distributions in the third resonance region is consistent with strong contributions of an N*→Nσ decay for the proton, while the reaction is dominated by a sequential decay via a Δπ intermediate state for the neutron. Here, the data are compared to predictions from the Two-Pion-MAID model and the Bonn-Gatchina coupled-channel analysis.},
doi = {10.1140/epja/i2015-15142-8},
journal = {European Physical Journal. A},
number = 11,
volume = 51,
place = {United States},
year = {2015},
month = {11}
}

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