BES results on J/psi decays and charmonium transitions

摘要

Results are reported based on samples of 58 million J/psi and 14 million psi(2S) decays obtained by the BESII experiment. Improved branching fraction measurements are determined, including branching fractions for J/psi -> pi(+)pi(-)pi(0), psi (2S) -> pi(0)J/psi, eta J/psi, pi(0)pi(0)J/psi, anything J/psi, and psi (2S) -> gamma chi(c1), gamma chi(c2) -> gamma gamma J/psi. The decay J/psi -> omega pi(+)pi(-) studied. At low pi pi mass, a large, broad peak due to the a is observed, and its pole position is determined. Results are presented on psi (2S) and J/psi hadronic decays to K(S)(0)pK(-)(n) over bar and K-S(0)(p) over barK(+)n final states. No significant Theta (1540) signal, the pentaquark candidate, is observed, and upper limits are set. An enhancement near the m(p) + MA mass threshold is observed in the p Lambda invariant mass spectrum from J/psi -> pK(-)Lambda+c.c. decays. It can be fit with an S-wave Breit-Wigner resonance with a mass m = 2075 +/- 12 (stat) +/- 5 (syst) MeV and a width of Gamma = 90 +/- 35 (stat) +/- 9 (syst) MeV.