Speaker
Description
Study of eta'(958) meson property in nuclear medium is fascinating because it may probe into the mechanism of hadron mass generation. A large mass reduction of eta' meson in nuclear medium owing to its UA(1) anomaly is expected in several model calculations. If the eta' mass is reduced in a nucleus, the eta' meson and the nucleus can form a bound state. We searched for the eta'-nucleus bound states via missing mass spectroscopy of the 12C(gamma, p) reaction. The experiment was carried out in the LEPS2 beam line at SPring-8 using GeV photon beam. Produced particles were measured using the BGOegg detector system. Suppression of background events arising from multiple meson productions is a key to observe eta'-bound states. For this purpose, we tagged an eta-proton pair, which is expected to be emitted in the eta'N->etaN absorption process of a bound eta' in a nucleus. We report the experimental results and comparisons with theoretical calculations.
