分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： Using an electron-positron collision data sample of 2.93 fb collected at a center-of-mass energy of √s = 3.773 GeV with the BESIII detector, we present the first search for the radiative leptonic decay D+ →+γe+νe.+ The analysis is performed with a double tag method. We do not+ observ+e a significant D → γe νe signal, and obtain an upper limit on the branching fraction of D → γe νe decay with the energy of radiative photon larger than 10 MeV of 3.0 × 10 at the 90% confidence level.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： By analyzing the large-angle Bhabha scattering events e+e− → (γ)e+e and diphoton events e e → γγ for the data sets collected at center-of-mass (c.m.) energies between 2.2324 and 4.5900 GeV (131 energy points in total) with the upgraded Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider (BEPCII), the integrated luminosities have been measured at the different c.m. energies, individually. The results are the important inputs for R value and J/ψ resonance parameter measurements.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： We present an amplitude analysis of the decay D0 → K−π+π+π− based on a data sample of 2.93 fb−1 acquired by the BESIII detector at the ψ(3770) resonance. With a nearly background free sample of about 16000 events, we investigate the substructure of the decay and determine the relative fractions and the phases among the different intermediate processes. Our amplitude model includes the two-body decays D0 → K¯ ∗0ρ0, D0 → K−a+(1260) and D0 → K−(1270)π+, the three-body decays D0 → K¯ ∗0π+π− and D0 → K−π+ρ0, as well as the four-body nonresonant decay D0 → K−π+π+π−. The dominant intermediate process is D0 → K−a+(1260), accounting for a fit fraction of 54.6%.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： Based on e+e− annihilation data samples collected with the BESIII detector at the BEPCII collider at 13 center of mass energies from 4.008 to 4.600 GeV, measurements of the Born cross section of e+e− → pp¯π0 are performed. No significant resonant structure is observed in the measured energy-dependent cross section. The upper limit on the Born cross section of e+e− → Y (4260) → pp¯π0 at the 90% C.L. is determined to be 0.01 pb.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： Using 106 million ψ(3686) events collected with the BESIII detector, we measure multipole amplitudes for the decay ψ(3686) → γχc1,2 → γγJ/ψ beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole amplitude for ψ(3686) → γχc1,2 → γγJ/ψ and the normalized electric-octupole am-plitudes for ψ(3686) → γχc2, χc2 → γJ/ψ are determined. The M2 amplitudes for ψ(3686) → γχc1 and χc1,2 → γJ/ψ are found to differ significantly from zero and are consistent with theoretical pre-dictions. We also obtain the ratios of M2 contributions of ψ(3686) and J/ψ decays to χc1,2, b /b =1.35 ± 0.72 and a /a = 0.617 ± 0.083, which agree well with theoretical expectations. By consider-ing the multipole contributions of χc1,2, we measure the product branching fractions for the cascade decays ψ(3686) → γχc0,1,2 → γγJ/ψ and search for the process ηc(2S) → γJ/ψ through ψ(3686) → γηc(2S). The product branching fraction for ψ(3686) → γχc0 → γγJ/ψ is 3σ larger than published measure-ments, while those of ψ(3686) → γχc1,2 → γγJ/ψ are consistent. No significant signal for the decay ψ(3686) → γηc(2S) → γγJ/ψ is observed, and the upper limit of the product branching fraction at the 90% confidence level is determined.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： We study the decays of J/ψ and ψ(3686) to the final states Σ(1385)0 ¯Σ(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)0 ¯Σ(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)0 ¯Σ(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.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： The decays of χc2 → K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2 → K∗K, χc2 → a±(1320)π∓/a02(1320)π0 and χc2 → ρ(770)±π∓ are measured. Here K∗K denotes both K∗±K∓ and its isospin-conjugated process K∗0K0 + c.c., and K∗ denotes the resonances K∗(892), K2∗(1430) and K3∗(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2 → K∗(892)K are more than 10 times larger than the upper limit of χc2 → ρ(770)±π∓, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： Based on a sample of 1.31 billion J/ψ events collected with the BESIII detector, we report the study of the doubly radiative decay η′ → γγπ0 for the first time, where the η′ meson is produced via the J/ψ → γη′ decay. The branching fraction of η′ → γγπ0 inclusive decay is measured to be B(η′ → γγπ0)Incl. = (3.20 ± 0.07(stat) ± 0.23(sys)) × 10−3, while the branching fractions of the dominant process η′ → γω and the nonresonant component are determined to be B(η′ → γω) ×B(ω → γπ0) =(23.7 ± 1.4(stat) ± 1.8(sys)) × 10−4 and B(η′ → γγπ0)NR = (6.16 ± 0.64(stat) ± 0.67(sys)) × 10−4, respectively. In addition, the Mγ2γ -dependent partial widths of the inclusive decay are also presented.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： Using (223.7 ± 1.4) × 106 J/ψ events accumulated with the BESIII detector, we study ηc decays to φφ and ωφ final states. The branching fraction of ηc → φφ is measured to be Br(ηc → φφ) =(2.5 ± 0.3+−0.3 ± 0.6) × 10−3, where the first uncertainty is statistical, the second is systematic, and the third is from the uncertainty of Br(J/ψ → γηc). No significant signal for the double Okubo-Zweig-Iizuka suppressed decay of ηc → ωφ is observed, and the upper limit on the branching fraction is determined to be Br(ηc → ωφ) < 2.5 × 10−4 at the 90% confidence level.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： We report the first measurement of the absolute branching fraction for +c ! μ+νμ. This measurement is based on a sample of e+e− annihilation data at a center-of-mass energy of ps = 4.6 GeV collected with the BESIII detector at the BEPCII storage rings. The sample corresponds to an integrated luminosity of 567 pb−1. The branching fraction is determined to be B( +c ! μ+νμ) = (3.49 ± 0.46(stat) ± 0.27(syst))%. In addition, we calculate the ratio B( +c ! μ+νμ)/B( +c ! e+νe) to be 0.96 ± 0.16(stat) ± 0.04(syst).
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： We report the first direct measurement of decays of the A+c baryon involving the neutron. The analysis is performed using 567 pb−1 of e+e− collision data collected at √s = 4.599 GeV with the BESIII detector at the BEPCII collider. We observe the decay A+c→nK0S π+ and measure the absolute branching fraction to be B(Α+c→nK0S π+) = (1.82 ± 0.23(stat) ± 0.11(syst))%. A comparison to B(Α+c → p( Kπ )0) provides an important test of isospin symmetry and final stateinteractions.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-11-10
摘要： The cross section for the process e+e− ! π+π−J/ψ is measured precisely at center-of-mass energies from 3.77 to 4.60 GeV using 9 fb−1 of data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in a fit to the cross section. The first resonance has a mass of (4222.0 ± 3.1±1.4) MeV/c2 and a width of (44.1±4.3±2.0) MeV, while the second one has a mass of (4320.0±10.4± 7.0) MeV/c2 and a width of (101.4+25.3−19.7 ± 10.2) MeV, where the first errors are statistical and second ones are systematic. The first resonance agrees with the Y (4260) resonance reported by previous experiments. The precision of its resonant parameters is improved significantly. The second resonance is observed in e+e− ! π+π−J/ψ for the first time. The statistical significance of this resonance is estimated to be larger than 7.6σ.The mass and width of the second resonance agree with the Y (4360) resonance reported by the BABAR and Belle experiments within errors. Finally, the Y (4008) resonance previously observed by the Belle experiment is not confirmed in the description of the BESIII data.
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