Based on a sample of 5.8×107 J/ψ events taken with the BESII detector, the branching fractions of J/ψ→2(π ⁺ π ^- )η and J/ψ→3(π ⁺ π ^- )η are measured for the first time to be (2.26±0.08±0.27)×10 ^-3 and (7.24±0.96±1.11)×10 ^-4 , respectively. © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

The absolute branching fraction for the decay D+→μ+ν has been directly measured based on a data sample of about 33 pb ^-1 collected around s=3.773 GeV with the BES-II detector at the BEPC collider. A total of 5321±149±160 D- mesons are reconstructed in nine hadronic decay modes. In the system recoiling against these singly tagged D- mesons, 2.67±1.74 purely leptonic decay events of D+→μ+νμ are observed. Those yield the branching fraction of BF(D+→μ+νμ)=(0. 122-0.053+0.111±0.010)%, and a corresponding value of the pseudoscalar decay constant fD+=(371-119+129±25) MeV. © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

Based on 5.8 × 10 ⁷ J/ψ events detected in BESII, the branching fractions of J/ψ → φη and φη′ are measured for different η and η decay modes. The results are significantly higher than previous measurements. An upper limit on B(J/ψ → φη ⁰ ) is also obtained. © 2005 The American Physical Society.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physical Review D Particles Fields Gravitation and Cosmology

2005

The decay ψ′→π+π-π0 is analyzed using a sample of 14 million ψ′ events taken with the BESII detector at the BEPC, and the branching fraction is measured to be B(ψ′→π+π-π0)= (18.1±1.8±1.9)×10-5. A partial wave analysis is carried out using the helicity amplitude method. ψ′→ρ(770)π is observed, and the branching fraction is measured to be B(ψ′→ρ (770)π)=(5.1±0.7±1.1)×10-5, where the first error is statistical and the second one is systematic. A high mass enhancement with mass around 2.15 GeV/c2 is also observed. Attributing this enhancement to the ρ(2150) resonance, the branching fraction is measured to be B(ψ′→ρ(2150)π→π+π-π0)=(19.4±2.5-3. 4+11.5)×10-5. The results will help in the understanding of the longstanding "ρπ puzzle" between J/ψ and ψ′ hadronic decays. © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

Using data collected with the BESII detector at Beijing Electron-Positron Collider, the measurements of relative branching fractions for seven Cabibbo-suppressed hadronic weak decays D ⁰ → K ^- K ⁺ , π ^- π ⁺ , K ^- K ⁺ π ⁺ π ^- and π ^- π ⁺ π ⁺ π ^- , D ⁺ → K̄ ⁰ K ⁺ , K ^- K ⁺ π ⁺ and π ^- π ⁺ π ⁺ are presented. © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

The branching fractions for the inclusive Cabibbo-favored K̄ ^*0 and Cabibbo-suppressed K ^*0 decays of D mesons are measured based on a data sample of 33 pb ^-1 collected at and around the center-of-mass energy of 3.773 GeV with the BES-II detector at the BEPC collider. The branching fractions for the decays D ⁺⁽⁰⁾ → K̄ ^*0 (892)X and D ⁰ → K ^*0 (892)X are determined to be BF(D ⁰ → K̄ ^*0 X) = (8.7 ± 4.0 ± 1.2)%, BF(D ⁺ → K̄ ^*0 X) = (23.2 ± 4.5 ± 3.0)% and BF(D ⁰ → K ^*0 X) = (2.8 ± 1.2 ± 0.4)%. An upper limit on the branching fraction at 90% C.L. for the decay D ⁺ → K ^*0 (892)X is set to be BF(D ⁺ → K ^*0 X) < 6.6%. © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

Decays of χ c0,2 →ωω are observed for the first time using a sample of 14.0×10 ⁶ ψ(2S) events collected with the BESII detector. The branching ratios are determined to be B(χ c0 →ωω)=(2.29±0.58±0.41) ×10 ^-3 and B(χ c2 →ωω)=(1. 77±0.47±0.36)×10 ^-3 , where the first errors are statistical and the second systematic. The significances of the two signals are 4.4σ and 4.7σ, respectively. © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen Y. B.;Chu Y. P.;Cui X. Z.;Deng Z. Y.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

First observations of χ c0 , χ c1 , and χ c2 decays to π ⁺ π-K S⁰ K S⁰ and K ⁺ K ^- K S⁰ K S⁰ , as well as ψ(2S) decay to π ⁺ π ^- K S⁰ K S⁰ , are presented. The branching fractions of these decay channels are determined using 14×10 ⁶ ψ(2S) events collected at BESII/BEPC. The branching fractions of χ c0 ,χ c2 →K S⁰ K S⁰ are measured with improved statistical precision. © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

Cross sections for e ⁺ e ^- →pp̄ have been measured at 10 center-of-mass energies from 2.0 to 3.07 GeV by the BESII experiment at the BEPC, and proton electromagnetic form factors in the time-like region have been determined. © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen Y. B.;Chu Y. P.;Cui X. Z.;Deng Z. Y.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

Using 58 million J/ψ events collected by the BES-II detector at the BEPC, the decays J/ψ→ΛΛ̄ and Σ ⁰ Σ̄ ⁰ are analysed. The branching fractions are measured to be Br(J/ψ→ΛΛ̄)=(2.03±0. 03±0.15)×10 ^-3 and Br(J/ψ→Σ ⁰ Σ̄ ⁰ )=(1.33±0.04±0.11) ×10 ^-3 . The angular distribution is of the form dN/dcosθ=N 0 (1+αcos ² θ), with α=0.65±0.11±0.03 for J/ψ→ΛΛ̄ and α=-0.24±0.19±0.07 for J/ψ→Σ ⁰ Σ̄ ⁰ . © 2005 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen Y. B.;Chu Y. P.;Cui X. Z.;Deng Z. Y.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2006