F. Pheron, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, H. Berghaeuser, B. Boillat, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, B. Demissie, M. Dieterle, E. J. Downie, P. Drexler, D. I. Glazier, E. Heid, L. V. Fil'kov, D. Hornidge, D. Howdle, O. Jahn, I. Jaegle, T. C. Jude, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, M. Kotulla, A. Kulbardis, S. P. Kruglov, B. Krusche, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, E. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, B. Oussena, P. Pedroni, A. Polonski, S. N. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, M. H. Sikora, D. I. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, D. Werthmueller, L. Witthauer, F. Zehr
Coherent photoproduction of $\eta$-mesons off $^3$He, i.e. the reaction
$\gamma ^3{He}\rightarrow \eta ^3{He}$, has been investigated in the
near-threshold region. The experiment was performed at the Glasgow tagged
photon facility of the Mainz MAMI accelerator with the combined Crystal Ball -
TAPS detector. Angular distributions and the total cross section were measured
using the $\eta\rightarrow \gamma\gamma$ and $\eta\rightarrow 3\pi^0\rightarrow
6\gamma$ decay channels. The observed extremely sharp rise of the cross section
at threshold and the behavior of the angular distributions are evidence for a
strong $\eta {^3{He}}$ final state interaction, pointing to the existence of a
resonant state. The search for further evidence of this state in the excitation
function of $\pi^0$-proton back-to-back emission in the $\gamma
^3{He}\rightarrow \pi^0 pX$ reaction revealed a very complicated structure of
the background and could not support previous conclusions.
View original:
http://arxiv.org/abs/1201.6517
No comments:
Post a Comment