Purely leptonic decays of the charged D meson have been studied using the reaction e+e- → D*+D- at a center of mass energy of 4.03 GeV. A search was performed for D → μνμ recoiling against a D0 or D+ which had been reconstructed from its hadronic decay products. A single event candidate was found in the reaction e+e- → D*+D-, where D*+ → π+D0 with the D0 → K-π+, and the recoiling D- decaying via D- → μ-ν̄μ. This yields a branching fraction value B(D → μνμ) = 0.08+0.16+0.05-0.05-0.02%, and a corresponding value of the pseudoscalar decay constant fD = 300+180+80-150-40 MeV. © 1998 Elsevier Science B.V. All rights reserved.

The cross section for e+e-→ρπ has been measured by the BES detector at BEPC at center-of-mass energies covering a 40 MeV interval spanning the J/ψresonance. The data are used to search for the vector gluonium state hypothesized by Brodsky, Lepage, and Tuan as an explanation of the ρπ puzzle in charmonium physics. The shape of the ρπ cross section is compatible with that of the total hadronic cross section. No distortions indicating the presence of a vector glueball are seen. © 1996 The American Physical Society.

Using a sample of 3.8 M ψ(2S) events accumulated with the BES detector, the process ψ(2S) →π+π-J/ψ is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D wave amplitude, as well as S wave. On the other hand, the J/ψ-(π+π-) relative angular momentum is consistent with being pure S wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter κ, predicts that D wave pions should be present. We determine κ=0.183 ±0.002±0.003 based on the joint mππ-cos θπ* distribution. The fraction of D wave amplitude as a function of mππ is found to decrease with increasing mππ, in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions. ©2000 The American Physical Society.

A sample of 3.79 × 106ψ(2S) events is used to study the decays of charmonium to axial-vector plus pseudoscalar mesons. The branching fraction for the decay ψ(2S) → b±1(1235)π∓ agrees with expectations based on scaling the corresponding J/ψ branching fraction. Flavor-SU(3)-violating K1(1270)- K1(1400) asymmetries with opposite character for ψ(2S) and J/ψ decays are observed. This contrasting behavior cannot be accommodated by adjustments of the singlet-triplet mixing angle. © 1999 The American Physical Society.

The absolute inclusive branching fraction of (Formula presented) has been measured from data collected by the BES detector at a center-of-mass energy of 4.03 GeV, corresponding to an integrated luminosity of 22.3 pb(Formula presented). At this energy, direct pair production (Formula presented) has been observed. We have selected (Formula presented) candidate events by reconstructing five hadronic decay modes (Formula presented), (Formula presented), (Formula presented), (Formula presented) and (Formula presented) and have searched for inclusive (Formula presented)’s in the recoiling (Formula presented). We observed three recoiling (Formula presented)’s in the 166.4 (Formula presented) 31.8 (Formula presented) candidate events, which leads to the absolute branching fraction (Formula presented) and (Formula presented). © 1998 The American Physical Society.

The first measurement of (Formula presented) and an upper limit for (Formula presented) are determined from 22.3 (Formula presented) of (Formula presented) annihilation data at a c.m. energy of 4.03 GeV. The data were recorded by the Beijing Spectrometer (BES) at BEPC. A recoil charge method is applied to charm threshold data to determine the charge of the D meson in the recoil from (Formula presented) reconstructed (Formula presented) (Formula presented) mesons. The branching fractions (Formula presented) and (Formula presented) are determined from 10 events with a reconstructed D and a recoiling (Formula presented) In addition, a 90% C.L. upper limit of (Formula presented) is determined from a search for semileptonic decays of the (Formula presented) © 2000 The American Physical Society.

A search is performed for the production of the (Formula presented) in (Formula presented) annihilation at a center-of-mass energy of 4.03 GeV using the BES detector operated at the Beijing Electron Positron Collider (BEPC). The kinematic features of the reconstructed (Formula presented) signal are consistent with its being produced only in association with an energetic photon resulting from initial state radiation (ISR). Limits are placed on (Formula presented) production from the decay of unknown charmonia or metastable hybrids that might be produced in (Formula presented) annihilations at 4.03 GeV. Under the assumption that the observed cross section for (Formula presented) production is due entirely to ISR, the partial width (Formula presented) of the (Formula presented) is measured to be (Formula presented). © 1998 The American Physical Society.

Using a sample of 3.8 M (Formula presented) events accumulated with the BES detector, the process (Formula presented) is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D wave amplitude, as well as S wave. On the other hand, the (Formula presented) relative angular momentum is consistent with being pure S wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter (Formula presented) predicts that D wave pions should be present. We determine (Formula presented) based on the joint (Formula presented) distribution. The fraction of D wave amplitude as a function of (Formula presented) is found to decrease with increasing (Formula presented) in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions. © 2000 The American Physical Society.

The decays of the ψ(2S) into vector plus tensor meson final states have been studied for the first time using the BES detector. We determine upper limits on branching fractions for ψ(2S) decays into ωf2, ρa2, K*0K*02 + c.c., and φf'2(1525) that are, in each case, significantly smaller than the corresponding branching fractions for the J/ψ meson, scaled according to the expectations of perturbative QCD. © 1998 The American Physical Society.

Hadronic decays of the P-wave spin-triplet charmonium states (Formula presented) are studied using a sample of (Formula presented) decays collected by the BES detector operating at the BEPC storage ring. Branching fractions for the decays (Formula presented) (Formula presented) (Formula presented) (Formula presented) (Formula presented) and (Formula presented) are measured for the first time, and those for (Formula presented) (Formula presented) (Formula presented) and (Formula presented) are measured with improved precision. In addition, we determine the masses of the (Formula presented) and (Formula presented) to be (Formula presented) and (Formula presented) © 1999 The American Physical Society.