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We observe a narrow enhancement near 2m(p) in the invariant mass spectrum of pp pairs from radiative J/psi-->gammapp decays. No similar structure is seen in J/psi-->pi(0)pp decays. The results are based on an analysis of a 58 x 10(6) event sample of J/psi decays accumulated with the BESII detector at the Beijing electron-positron collider. The enhancement… (More)
We report values of R = sigma(e(+)e(-)-->hadrons)/sigma(e(+)e(-)-->mu(+)mu(-)) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.
The processes ψ(2S) → γπ+π−, γK+K− and γpp̄ have been studied using a sample of 3.79 × 106 ψ(2S) decays. We determine the total width of the χc0 to be Γ tot χc0 = 14.3 ± 2.0 ± 3.0 MeV. We present the first measurement of the branching fraction B(χc0 → pp̄) = (15.9 ± 4.3 ± 5.3) × 10−5, where the first error is statistical and the second one systematic.… (More)
In a sample of 58 million J/ψ events collected with the BES II detector, the process J/ψ → γηc is observed in five different decay channels: γKKππ, γππππ, γKK Sπ ∓ (with K S → ππ), γφφ (with φ→ KK) and γpp̄. From a combined fit of all five channels, we determine the mass and full-width of ηc to be mηc = 2977.5 ± 1.0 (stat.) ± 1.2 (syst.) MeV/c and Γηc =… (More)
A comparison of the rates for ψ(2S) → π+π−J/ψ, J/ψ → l+l− and J/ψ → anything is used to determine the J/ψ leptonic branching fractions. The results are B(J/ψ → e+e−) = (5.90 ± 0.05 ± 0.10)% and B(J/ψ → μ+μ−) = (5.84 ± 0.06 ± 0.10)%, where the first error is statistical and the second is systematic. Assuming lepton universality, the leptonic branching… (More)
(BES Collaboration) J. Z. Bai, Y. Ban, J. G. Bian, X. Cai, J. F. Chang, H. F. Chen, H. S. Chen, J. Chen, Jie Chen, J. C. Chen, Y. B. Chen, S. P. Chi, Y. P. Chu, X. Z. Cui, Y. M. Dai, Y. S. Dai, L. Y. Dong, S. X. Du, Z. Z. Du, W. Dunwoodie, J. Fang, S. S. Fang, C. D. Fu, H. Y. Fu, L. P. Fu, C. S. Gao, M. L. Gao, Y. N. Gao, M. Y. Gong, W. X. Gong, S. D. Gu,… (More)
Using a sample of 5.8 × 107J/ψ events, the Beijing Spectrometer experiment has searched for the decay J/ψ → eμ. Four candidates, consistent with the estimated background, are observed, and an upper limit on the branching fraction of J/ψ → eμ of 1.1× 10−6 at the 90 % C.L. is obtained.
J. Z. Bai, J. G. Bian, I. Blum, Z. W. Chai, G. P. Chen, H. F. Chen, J. Chen, J. C. Chen, Y. Chen, Y. B. Chen, Y. Q. Chen, B. S. Cheng, X. Z. Cui, H. L. Ding, L. Y. Ding, L. Y. Dong, Z. Z. Du, W. Dunwoodie, S. Feng, C. S. Gao, M. L. Gao, S. Q. Gao, P. Gratton, J. H. Gu, S. D. Gu, W. X. Gu, Y. F. Gu, Y. N. Guo, S. W. Han, Y. Han, F. A. Harris, J. He, J. T.… (More)
The processes ψ(2S) → γπ+π−, γK+K− and γpp̄ have been studied using a sample of 3.7× 106 produced ψ(2S) decays. We determine the total width of the χc0 to be Γ tot χc0 = 14.3± 2.0± 3.0 MeV. We present the first measurement of the branching fraction B(χc0 → pp̄) = (16.3± 4.4± 5.4)× 10−5, where the first error is statistical and the second one systematic.… (More)
We report first measurements of the branching fractions: B(ψ2S → γη ) = (1.54±0.31±0.20)×10−4 and B(ψ2S → γη) = (0.53±0.31±0.08)×10 −4 . The ψ(2S) → γη result is consistent with expectations of a model that considers the possibility of η-ηc mixing. The ratio of the ψ(2S) → γη ′ and ψ(2S) → γη rates is used to determine the pseudoscalar octet-singlet mixing… (More)