Study of charmonium(-like) states via ISR at Belle**Talk given at the BES-Belle-CLEO-BaBar joint workshop on charm physics, Beijing, Chnia, November 26–27, 2007. Supported by National Natural Science Foundation of China (10775142) and 100 Talents Program of CAS (U-25)

Abstract

The cross sections for e+e− → π+π−J/ψ, π+π−ψ(2S), K+K−J/ψ, DD̄, D0D−π++c.c., D*D̄+c.c., and D*D̄* are measured using data sample collected on or near the Υ(4S) resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c2, corresponding to the so called Y(4260), is observed in π+π−J/ψ final state. In addition, there is another cluster of events at around 4.05 GeV/c2. Two resonant structures are observed in the π+π−ψ(2S) invariant mass distribution, one at 4361±9±9 MeV/c2 with a width of 74±15±10 MeV/c2, and another at 4664±11±5 MeV/c2 with a width of 48±15±3 MeV/c2. The rich structures observed in all these final states indicate that our understanding of the vector charmonium states above the open charm threshold is still poor, let alone the other possible dynamics such as charmonium hybrids or final state re-scattering and so on.