Quasi-free photoproduction of η-mesons off 3He nuclei

L. Witthauer, D. Werthmüller, I. Keshelashvili, P. Aguar-Bartolomé, J. Ahrens, J. R.M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, B. Demissie, M. Dieterle, E. J. Downie, P. Drexler, L. V. Fil'kovA. Fix, D. I. Glazier, D. Hamilton, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, I. Jaegle, O. Jahn, T. C. Jude, A. Käser, V. L. Kashevarov, R. Kondratiev, M. Korolija, S. P. Kruglov, B. Krusche, A. Kulbardis, V. Lisin, K. Livingston, I. J.D. Macgregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, E. McNicoll, V. Metag, D. G. Middleton, A. Mushkarenkov, B. M.K. Nefkens, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. Prakhov, J. Robinson, G. Rosner, M. Rost, T. Rostomyan, S. Schumann, M. H. Sikora, D. Sobe, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzag, D. P. Watts

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Abstract

Quasi-free photoproduction of η-mesons has been measured off nucleons bound in 3He nuclei for incident photon energies from the threshold region up to 1.4 GeV. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with an almost 4π covering electromagnetic calorimeter, combining the TAPS and Crystal Ball detectors. The η-mesons were detected in coincidence with the recoil nucleons. This allowed a comparison of the production cross section off quasi-free protons and quasi-free neutrons and a full kinematic reconstruction of the final state, eliminating effects from nuclear Fermi motion. In the S11(1535) resonance peak, the data agree with the neutron/proton cross section ratio extracted from measurements with deuteron targets. More importantly, the prominent structure observed in photoproduction off quasi-free neutrons bound in the deuteron is also clearly observed. Its parameters (width, strength) are consistent with the expectations from the deuteron results. On an absolute scale the cross sections for both quasi-free protons and neutrons are suppressed with respect to the deuteron target pointing to significant nuclear final-state interaction effects.

Original languageEnglish
Article number154
Pages (from-to)1-18
Number of pages18
JournalEuropean Physical Journal A
Volume49
Issue number12
DOIs
Publication statusPublished - 1 Jan 2013

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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    Witthauer, L., Werthmüller, D., Keshelashvili, I., Aguar-Bartolomé, P., Ahrens, J., Annand, J. R. M., Arends, H. J., Bantawa, K., Beck, R., Bekrenev, V., Braghieri, A., Branford, D., Briscoe, W. J., Brudvik, J., Cherepnya, S., Demissie, B., Dieterle, M., Downie, E. J., Drexler, P., ... Watts, D. P. (2013). Quasi-free photoproduction of η-mesons off 3He nuclei. European Physical Journal A, 49(12), 1-18. [154]. https://doi.org/10.1140/epja/i2013-13154-0