Observation of a cusp-like structure in the γp → K+Σ0 cross section at forward angles and low momentum transfer
T. C. Jude, S. Alef, P. Bauer, D. Bayadilov, R. Beck, A. Bella, J. Bieling, A. Braghieri, P. L. Cole, D. Elsner, R. Di Salvo, A. Fantini, Oliver Freyermuth, F. Frommberger, F. Ghio, S. Goertz, A. Gridnev, D. Hammann, J. Hannappel, Katrin Kohl, N. Kozlenko, A. Lapik, P. Levi Sandri, V. Lisin, G. Mandaglio, F. Messi, R. Messi, D. Moricciani, V. Nedorezov, V. A. Nikonov, D. Novinskiy, P. Pedroni, A. Polonskiy, B. Reitz, M. Romaniuk, A. Sarantsev, G. Scheluchin, H. Schmieden, A. Stuglev, V. V. Sumachev, V. Vegna, В. И. Тараканов, T. Zimmermann
Abstract
The γp→K+Σ0 differential cross section at extremely forward angles was measured at the BGOOD experiment. A three-quarter drop in strength over a narrow range in energy and a strong dependence on the polar angle of the K+ in the centre-of-mass of the reaction is observed at a centre-of-mass energy of 1900 MeV. Residing close to multiple open and hidden strangeness thresholds, the structure appears consistent with meson-baryon threshold effects which may contribute to the reaction mechanism.