247 research outputs found
Study of J /ψ and ψ (3686) decay to ΛΛ¯ and Σ0Σ¯0 final states
No full textUsing 1310.6 × 106 J=ψ and 447.9 × 106 ψð3686Þ events collected with the BESIII detector at the BEPCII eþe− collider, the branching fractions and the angular distributions of J=ψ and ψð3686Þ decays to ΛΛ¯ and Σ0Σ¯ 0 final states are measured. The branching fractions are determined, with much improved precision, to be 19.43 0.03 0.33, 11.64 0.04 0.23, 3.97 0.02 0.12 and 2.44 0.03 0.11 for J=ψ → ΛΛ¯, J=ψ → Σ0Σ¯ 0, ψð3686Þ → ΛΛ¯ and ψð3686Þ → Σ0Σ¯ 0, respectively. The polar angular distributions of ψð3686Þ decays are measured for the first time, while those of J=ψ decays are measured with much improved precision. In addition, the ratios of branching fractions Bðψð3686Þ→ΛΛ¯Þ BðJ=ψ→ΛΛ¯Þ and Bðψð3686Þ→Σ0Σ¯ 0Þ BðJ=ψ→Σ0Σ¯ 0Þ are determined to test the “12% rule.
Study of J /ψ and ψ (3686) decay to ΛΛ¯ and Σ0Σ¯0 final states
No full textUsing 1310.6 × 106 J=ψ and 447.9 × 106 ψð3686Þ events collected with the BESIII detector at the BEPCII eþe− collider, the branching fractions and the angular distributions of J=ψ and ψð3686Þ decays to ΛΛ¯ and Σ0Σ¯ 0 final states are measured. The branching fractions are determined, with much improved precision, to be 19.43 0.03 0.33, 11.64 0.04 0.23, 3.97 0.02 0.12 and 2.44 0.03 0.11 for J=ψ → ΛΛ¯, J=ψ → Σ0Σ¯ 0, ψð3686Þ → ΛΛ¯ and ψð3686Þ → Σ0Σ¯ 0, respectively. The polar angular distributions of ψð3686Þ decays are measured for the first time, while those of J=ψ decays are measured with much improved precision. In addition, the ratios of branching fractions Bðψð3686Þ→ΛΛ¯Þ BðJ=ψ→ΛΛ¯Þ and Bðψð3686Þ→Σ0Σ¯ 0Þ BðJ=ψ→Σ0Σ¯ 0Þ are determined to test the “12% rule.
Study of J/ψ and ψ(3686)→Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0
No full textWe study the decays of J/ψ and ψ(3686) to the final states Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0 based on a single baryon tag method using data samples of (1310.6±7.0)×106 J/ψ and (447.9±2.9)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider. The decays to Σ(1385)0Σ¯(1385)0 are observed for the first time. The measured branching fractions of J/ψ and ψ(3686) to Ξ0Ξ¯0 are in good agreement with, and much more precise than, the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for J/ψ→Σ(1385)0Σ¯(1385)0, α=−0.64±0.03±0.10, is found to be negative, different to the other decay processes in this measurement. In addition, the “12% rule” and isospin symmetry in the decays of J/ψ and ψ(3686) to ΞΞ¯ and Σ(1385)Σ¯(1385) are tested
Study of J/ψ and ψ(3686)→Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0
No full textWe study the decays of J/ψ and ψ(3686) to the final states Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0 based on a single baryon tag method using data samples of (1310.6±7.0)×106 J/ψ and (447.9±2.9)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider. The decays to Σ(1385)0Σ¯(1385)0 are observed for the first time. The measured branching fractions of J/ψ and ψ(3686) to Ξ0Ξ¯0 are in good agreement with, and much more precise than, the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for J/ψ→Σ(1385)0Σ¯(1385)0, α=−0.64±0.03±0.10, is found to be negative, different to the other decay processes in this measurement. In addition, the “12% rule” and isospin symmetry in the decays of J/ψ and ψ(3686) to ΞΞ¯ and Σ(1385)Σ¯(1385) are tested
Complete Measurement of the Λ Electromagnetic Form Factors
No full textThe exclusive process e(+)e(-) -> Lambda(Lambda) over bar, with Lambda -> p pi(-) and (Lambda) over bar -> (p) over bar pi(+), has been studied at root s = 2.396 GeV for measurement of the timelike Lambda electric and magnetic form factors, G(E) and G(M). A data sample, corresponding to an integrated luminosity of 66.9 pb(-1), was collected with the BESIII detector for this purpose. A multidimensional analysis with a complete decomposition of the spin structure of the reaction enables a determination of the modulus of the ratio R = vertical bar G(E)/G(M)vertical bar and, for the first time for any baryon, the relative phase Delta Phi = Phi(E) - Phi(M). The resulting values are R = 0.96 +/- 0.14(stat) +/- 0.02(syst) and Phi(F) = 37 degrees +/- 12 degrees (stat) +/- 6 degrees (syst), respectively. These are obtained using the recently established and most precise value of the asymmetry parameter alpha(Lambda) = 0.750 +/- 0.010 measured by BESIII. In addition, the cross section is measured with unprecedented precision to be sigma = 118.7 +/- 5.3(stat) +/- 5.1(syst) pb, which corresponds to an effective form factor of vertical bar G vertical bar = 0.123 +/- 0.003(stat) +/- 0.003(syst). The contribution from two-photon exchange is found to be negligible. Our result enables the first complete determination of baryon timelike electromagnetic form factors
Measurements of absolute hadronic branching fractions of the Λc+ baryon
No full textWe report the first measurement of absolute hadronic branching fractions of Λ+c baryon at the Λ+cΛ¯−c production threshold, in the 30 years since the Λ+c discovery. In total, 12 Cabibbo-favored Λ+c hadronic decay modes are analyzed with a double-tag technique, based on a sample of 567 pb−1 of e+e− collisions at s√=4.599 GeV recorded with the BESIII detector. A global least-squares fitter is utilized to improve the measured precision. Among the measurements for twelve Λ+c decay modes, the branching fraction for Λ+c→pK−π+ is determined to be (5.84±0.27±0.23)%, where the first uncertainty is statistical and the second is systematic. In addition, the measurements of the branching fractions of the other 11 Cabibbo-favored hadronic decay modes are significantly improved
Study of χcJ decaying into фK*(892) K¯
No full textUsing a data sample of 106 million ψ(3686) events collected with the BESIII detector operated at the BEPCII storage ring, we study for the first time the decays χcJ→ϕK0SK±π∓ and χcJ→ϕK+K−π0 in the E1 radiative transition ψ(3686)→γχcJ. The decays are dominated by the three-body decay χcJ→ϕK∗(892)K¯. We measure branching fractions for this reaction via the neutral and charged K∗(892) and find them consistent with each other within the expectation of isospin symmetry. In the KK¯π invariant mass distribution, a structure near the K∗(892)K¯ mass threshold is observed, and the corresponding mass and width are measured to be 1412±4(stat)±8(sys) MeV/c2 and Γ=84±12(stat)±40(sys) MeV, respectively. The observed state favors an assignment to the h1(1380), considering its possible JPC and comparing its mass, width and decay mode to those reported in the Particle Data Group
Measurements of absolute hadronic branching fractions of the Λc+ baryon
No full textWe report the first measurement of absolute hadronic branching fractions of Λ+c baryon at the Λ+cΛ¯−c production threshold, in the 30 years since the Λ+c discovery. In total, 12 Cabibbo-favored Λ+c hadronic decay modes are analyzed with a double-tag technique, based on a sample of 567 pb−1 of e+e− collisions at s√=4.599 GeV recorded with the BESIII detector. A global least-squares fitter is utilized to improve the measured precision. Among the measurements for twelve Λ+c decay modes, the branching fraction for Λ+c→pK−π+ is determined to be (5.84±0.27±0.23)%, where the first uncertainty is statistical and the second is systematic. In addition, the measurements of the branching fractions of the other 11 Cabibbo-favored hadronic decay modes are significantly improved
Observation of a neutral structure near the DD¯* mass threshold in e+e− → (DD¯*)0π0 at √s = 4.226 and 4.257 GeV
No full textA neutral structure in the DD¯∗ system around the DD¯∗ mass threshold is observed with a statistical significance greater than 10σ in the processes e+e−→D+D*−π0+c.c. and e+e−→D0D¯*0π0+c.c. at s√=4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as Zc(3885)0. Assuming the presence of a resonance, its pole mass and width are determined to be [3885.7+4.3−5.7(stat)±8.4(syst)] MeV/c2 and [35+11−12(stat)±15(syst)] MeV, respectively. The Born cross sections are measured to be σ[e+e−→Zc(3885)0π0,Zc(3885)0→DD¯∗]=[77±13(stat)±17(syst)] pb at 4.226 GeV and [47±9(stat)±10(syst)] pb at 4.257 GeV. The ratio of decay rates B[Zc(3885)0→D+D*−+c.c.]/B[Zc(3885)0→D0D¯*0+c.c.] is determined to be 0.96±0.18(stat)±0.12(syst), consistent with no isospin violation in the process, Zc(3885)0→DD¯∗
Study of χcJ decaying into фK*(892) K¯
No full textUsing a data sample of 106 million ψ(3686) events collected with the BESIII detector operated at the BEPCII storage ring, we study for the first time the decays χcJ→ϕK0SK±π∓ and χcJ→ϕK+K−π0 in the E1 radiative transition ψ(3686)→γχcJ. The decays are dominated by the three-body decay χcJ→ϕK∗(892)K¯. We measure branching fractions for this reaction via the neutral and charged K∗(892) and find them consistent with each other within the expectation of isospin symmetry. In the KK¯π invariant mass distribution, a structure near the K∗(892)K¯ mass threshold is observed, and the corresponding mass and width are measured to be 1412±4(stat)±8(sys) MeV/c2 and Γ=84±12(stat)±40(sys) MeV, respectively. The observed state favors an assignment to the h1(1380), considering its possible JPC and comparing its mass, width and decay mode to those reported in the Particle Data Group
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