Differential cross section measurement of eta photoproduction on the proton from threshold to 1100 MeV
hep-ex
/ Authors
GRAAL collaboration, F. Renard, M. Anghinolfi, O. Bartalini, V. Bellini, J. -P. Bocquet, M. Capogni, M. Castoldi, P. Corvisiero, A. D'Angelo
and 26 more authors
J. -P. Didelez, R. Di Salvo, C. Gaulard, G. Gervino, F. Ghio, B. Girolami, M. Guidal, E. Hourany, V. Kouznetsov, R. Kunne, A. Lapik, P. Levi Sandri, A. Lleres, D. Moricciani, V. Nedorezov, L. Nicoletti, D. Rebreyend, N. Rudnev, M. Sanzone, C. Schaerf, M. -L. Sperduto, M. -C. Sutera, M. Taiuti, A. Turinge
/ Abstract
The differential cross section for the reaction p(gamma, eta p) has been measured from threshold to 1100 MeV photon laboratory energy. For the first time, the region of the S11(1535) resonance is fully covered in a photoproduction experiment and allows a precise extraction of its parameters at the photon point. Above 1000 MeV, S-wave dominance vanishes while a P-wave contribution is observed whose nature will have to be clarified. These high precision data together with the already measured beam asymmetry data will provide stringent constraints on the extraction of new couplings of baryon resonances to the eta meson.