I. Blum

First measurement of the branching fraction of the decay ψ(2S)→τ+τ-

The branching fraction of the ψ(2S) decay into τ+τ− has been measured for the first time using the BES detector at the Beijing Electron-Positron Collider. The result is Bττ = (2.71± 0.43± 0.55)× 10−3 , where the first error is statistical and the second is systematic. This value, along with those for the branching fractions into e+e− and μ+μ− of this resonance, satisfy well the relation predicted by the sequential lepton hypothesis. Combining all these values with the leptonic width of the resonance, the total width of the ψ(2S) is determined to be (252±37) keV. PACS numbers: 13.20.Gd, 14.40.Gx, 14.60.-z, 14.60.Fg Typeset using REVTEX

Measurement of the branching fraction of [Formula presented] inclusive semileptonic decay [Formula presented]

The absolute inclusive semileptonic branching fraction of the D{sub s} meson has been measured based on 22.3 pb{sup {minus}1} of e{sup +}e{sup {minus}} collision data collected with the Beijing Spectrometer at {radical} (s) =4.03GeV. At this energy, the D{sub s} are produced in pairs: e{sup +}e{sup {minus}}{r_arrow}D{sub s}{sup +}D{sub s}{sup {minus}}. We reconstructed 171{plus_minus}21{plus_minus}15 D{sub s} events in five hadronic decay modes. In the recoil system of these events, several D{sub s} inclusive semileptonic decays were observed and the branching fraction is estimated to be B(D{sub s}{sup +}{r_arrow}e{sup +}X)=(7.7{sub {minus}4.3{minus}2.1}{sup +5.7+2.4}){percent}. {copyright} {ital 1997} {ital The American Physical Society}Author(s): Bai, JZ; Bardon, O; Bian, JG; Blum, I; Breakstone, A; Burnett, T; Chai, ZW; Chen, GP; Chen, HF; Chen, J; Chen, JC; Chen, SM; Chen, Y; Chen, YB; Chen, YQ; Cheng, BS; Cowan, RF; Cui, XZ; Ding, HL; Du, ZZ; Dunwoodie, W; Fan, XL; Fang, J; Fero, M; Gao, CS; Gao, ML; Gao, SQ; Gratton, P; Gu, JH; Gu, SD; Gu, WX; Gu, YF; Guo, YN; Han, SW; Han, Y; Harris, FA; He, J; He, JT; He, M; Hitlin, DG; Hu, GY; Hu, JL; Hu, QH; Hu, T; Hu, XQ; Huang, XP; Huang, YZ; Izen, JM; Jia, QP; Jiang, CH; Jin, S; Jin, Y; Jones, L; Kang, SH; Ke, ZJ; Kelsey, MH; Kim, BK; Kong, D; Lai, YF; Lan, HB; Lang, PF; Lankford, A; Li, J; Li, PQ; Li, Q; Li, RB; Li, W; Li, WD; Li, WG; Li, XH; Li, XN; Lin, SZ; Lu, F; Liu, HM; Liu, J; Liu, JH; Liu, Q; Liu, RG; Liu, Y; Liu, ZA; Lou, XC; Lowery, B; Lu, JG; Lu, JY; Luo, SQ | Abstract: The absolute inclusive semileptonic branching fraction of the [Formula presented] meson has been measured based on [Formula presented] of [Formula presented] collision data collected with the Beijing Spectrometer at [Formula presented] At this energy, the [Formula presented] are produced in pairs: [Formula presented] We reconstructed [Formula presented] [Formula presented] events in five hadronic decay modes. In the recoil system of these events, several [Formula presented] inclusive semileptonic decays were observed and the branching fraction is estimated to be [Formula presented]