Ï c Decays and the Gluon Component of the î· â² , î· Mesons
L.A. Harland-Lang (Department of Physics and Astronomy, University College London, WC1E 6BT, UK); V.A. Khoze (Institute for Particle Physics Phenomenology, Durham University, Durham, DH1 3LE, UK, Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, St. Petersburg, 188300, Russia); M.G. Ryskin (Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, St. Petersburg, 188300, Russia); A.G. Shuvaev (Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, St. Petersburg, 188300, Russia)
The large mass of the η′ meson indicates that a sizeable gluon component is present in the meson wave function. However, the χc0 and χc2 decays to η′ mesons, which proceed via a purely gluonic intermediate state and we would therefore naïvely expect to be enhanced by such a component, are in fact relatively suppressed. We argue that this apparent contradiction may be resolved by a proper treatment of interference effects in the decay. In particular, by accounting for the destructive interference between the quark and gluon components of the η′ distribution function, in combination with a model for strange quark mass effects, we demonstrate that the observed χc(0,2)→η(′)η(′) branching ratios can be reproduced for a reasonable gluon component of the η′ , η mesons.
