PHYSICS ISSUES IN η′ DECAYS

Abstract

Studies of hadronic, radiative, and (semi–)leptonic decays of the η′ allow to shed light on a broad field of fundamental physics questions. Isospin symmetry breaking decays provide a well-suited tool to extract the light quark mass difference. Differential distributions in hadronic decays both test predictions obtained within ChPT approaches, and enclose information on the scalar meson sector. Precision measurements on radiative decay widths will constrain pseudoscalar mixing, the manifestation of QCD anomalies, and the structure of the η′. The latter is also subject of investigation in semileptonic decays probing the η′ transition form factor. The presently available experimental information is reviewed, and prospects for η′ decay physics with WASA at COSY are presented.