Recent Results of ψ(2S) Decays at BES

Using 14 million ψ(2S) data sample collected with BES at BEPC, ψ(2S) → V T , K SK 0 L (also J/ψ → K SK 0 L), and χcJ → BB decays are measured and compared with theoretical model predications. Charmonium physics is one of the interesting and intriguing field of particle physics. Charmonium provides us an excellent and simple system to study QCD, the production and decay mechanisms of heavy quarkonia and light hadron spectra from its decays, and can be treated non-relativistically. Using 14 M ψ(2S) data sample collected with BEijing Spectrometer (BES) at BEPC, ψ(2S) → V T , K SK 0 L (also J/ψ → K 0 SK 0 L), and χcJ → BB decays are measured and compared with theoretical model predications. The BES detector is described in detail in Ref.[1]. 1 Study of VT Channel in ψ(2S) Decay Both J/ψ and ψ(2S) decays are expected to be dominated by annihilation into three gluons, with widths that are proportional to the square of the cc wave function at the origin [2]. This yields the pQCD expectation (so-called “12 % ” rule) that Qh = Bψ(2S)→Xh BJ/ψ→Xh = Bψ(2S)→e+e− BJ/ψ→e+e− = (12.3± 0.7)% . (1) The violation of this rule was firstly revealed by MARK-I in VP channel (such as ρπ and KK channel) [3], which leads to famous “ρπ puzzle”. This phenomenon was then confirmed by BES at higher sensitivity [4]. Afterwards, BES collaboration presented many other observations, one of them is about VT channel. Based on BES-I 4 M data, the upper-limits of four VT channels, ωf2(1270), ρa2(1320), K (892)K∗ 2 (1430) 0 + c.c., and φf ′ 2(1525), were given [5]. Now with BES-II 14 M ψ(2S) date sample, all these upper-limits have been determined to be branching fractions. For these decay modes, studies focus on four-charged-track final states, such as KKππ or KKKK, and those with additional two photons decayed from π, such as ππππγγ or KKππγγ. After event selection, the invariant mass distributions for different channels are shown in Fig. 1. From the data fitting, the observed numbers of events are obtained, and M.C. simulation gives the corresponding efficiencies. The final results are shown in Table 1, together with statistical and systematic errors, and the resulting errors are at the level of 30 to 40 percent. Combining the corresponding results of J/ψ decay from PDG2002 [6], the Qh values were calculated as listed in Table 1. Comparing with 12 % rule, it is seen that the Qh value of VT channel is greatly suppressed.