Experimental studies of charmonia in two-photon collisions at Belle

Abstract

We report on the measurements of charmonium production in two-photon collisions performed with the Belle detector at the KEKB e + e − collider with the integrated luminosity up to about 400 fb−1. A new resonant state decaying to D D ¯ has been observed in the vicinity of 3.93 GeV/c2. From the measured angular distribution we found that it could be a candidate for the not yet found χ c 2 ′ , a radial excitation state of 3P2 charmonium. We have observed production of the χ c 0 and χ c 2 in the two-meson final states, π + π − , K + K − and K S 0 K S 0 and production of η c decaying to proton pairs. The χ c 2 production was also measured in the γ J / ψ decay mode. These three charmonia were also observed in their decays to the four-meson final states, where the meson is a charged pion or kaon. The products of the two-photon partial decay width and branching ratio were determined.