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
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 >> 核物理学 提交时间: 2016-09-14
摘要: We present here three analyses of semileptonic D-meson decays based on the 2.92 fb−1 of data collected by the BESIII experiment in 2010 and 2011 at the ψ(3770) peak. For the decay D+→K−π+e+νe, its branching fraction is measured over the whole mKπ region and in the K¯¯¯¯¯∗(892)0 window, respectively. A partial wave analysis (PWA) is performed, indicating an \emph{S}-wave contribution of about 6\%. The \emph{S}-wave phase and the form factors are measured by the PWA and in a model-independent way. For the decay D+→ωe+νe, an improved measurement of the branching fraction is performed and the form factors are determined for the first time. D+→ϕe+νe is searched and an improved upper limit at 90\% confidence level is set. For the decay D+→KLe+νe, its branching fraction is measured for the first time and the CP asymmetry is presented. The product of the hadronic form factor and the CKM matrix element, fK+(0)|Vcs|, is also determined in this decay.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: By analyzing a data set of 2.92 fb−1 of e+e− collision data taken at s√=3.773 GeV and 106.41×106 ψ(3686) decays taken at s√=3.686 GeV with the BESIII detector at the BEPCII collider, we measure the branching fraction and the partial decay width for ψ(3770)→γχc0 to be B(ψ(3770)→γχc0)=(6.88±0.28±0.67)×10−3 and Γ[ψ(3770)→γχc0]=(187±8±19) keV, respectively. These are the most precise measurements to date.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: We report the first absolute measurement of the branching fraction of Λ+c→Λe+νe. This measurement is based on 567 pb−1 of e+e− annihilation data produced at s√=4.599 GeV, which is just above the Λ+cΛ¯−cthreshold. The data were collected with the BESIII detector at the BEPCII storage rings. The branching fraction is determined to be B(Λ+c→Λe+νe)=(3.63±0.38(stat)±0.20(syst))%, representing a more than twofold improvement in precision upon previously published results. As the branching fraction for Λ+c→Λe+νeis the benchmark for those of other Λ+c semileptonic channels, our result provides a unique test of different theoretical models, which is the most stringent to date.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: The BESIII experiment at the Beijing Electron Positron Collider (BEPCII) has accumulated the world's largest samples of direct e+e− collisions in the τ-charm region. From the collected samples, which include e+e− annihilations at J/ψ, ψ′, ψ(3770) peaks and in the region from 3.8GeV to 4.6GeV, BESIII has produced many new physics results in the spectroscopy, transitions, and decays of charmonium(-like) states. This talk will cover the latest results over a wide range of topics from radiative and hadronic transitions among charmonium states, as well as the productions and decays of the XYZ states.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: Based on 2.92 fb−1 data taken at the center-of-mass energy s√=3.773 GeV with the BESIII detector, we report recent results on the decay constant fD+, the hadronic form factors, as well as the quark mixing matrix elements |Vcs(d)|, which are extracted from analyses of the leptonic decay D+→μ+νμ and the semileptonic decays D0→K(π)−e+νe, D+→K0Le+νe, D+→K−π+e+νe and D+→ω(ϕ)e+νe at BESIII.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: The BESIII experiment has collected world's largest direct e+e− colliding beam data at the J/ψ, ψ′, ψ(3770) and at and around the Y(4260). These data have enabled the study of hadrons at unprecedented precisions. We present results on the light hadron spectroscopy, production of hadrons in radiative decays of charmonia, observation of new excited N∗ baryons and of anomalous decays of the η/η′ states.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: In an analysis of a 2.92~fb−1 data sample taken at 3.773~GeV with the BESIII detector operated at the BEPCII collider, we measure the absolute decay branching fractions to be B(D0→K−e+νe)=(3.505±0.014±0.033)% and B(D0→π−e+νe)=(0.295±0.004±0.003)%. From a study of the differential decay rates we obtain the products of hadronic form factor and the magnitude of the CKM matrix element fK+(0)|Vcs|=0.7172±0.0025±0.0035 and fπ+(0)|Vcd|=0.1435±0.0018±0.0009. Combining these products with the values of |Vcs(d)| from the SM constraint fit, we extract the hadronic form factors fK+(0)=0.7368±0.0026±0.0036 and fπ+(0)=0.6372±0.0080±0.0044, and their ratio fπ+(0)/fK+(0)=0.8649±0.0112±0.0073. These form factors and their ratio are used to test unquenched Lattice QCD calculations of the form factors and a light cone sum rule (LCSR) calculation of their ratio. The measured value of fK(π)+(0)|Vcs(d)| and the lattice QCD value for fK(π)+(0) are used to extract values of the CKM matrix elements of |Vcs|=0.9601±0.0033±0.0047±0.0239 and |Vcd|=0.2155±0.0027±0.0014±0.0094, where the third errors are due to the uncertainties in lattice QCD calculations of the form factors. Using the LCSR value for fπ+(0)/fK+(0), we determine the ratio |Vcd|/|Vcs|=0.238±0.004±0.002±0.011, where the third error is from the uncertainty in the LCSR normalization. In addition, we measure form factor parameters for three different theoretical models that describe the weak hadronic charged currents for these two semileptonic decays. All of these measurements are the most precise to date.
分类: 物理学 >> 核物理学 提交时间: 2016-09-12
摘要: Based on ψ(3686) decays of 106 million, the 1.31 billion J/psi events and a data sample of ψ(3770) with 2.9 fb−1 integrated luminosity, many analyses are performed. Exclusively baryonic decays of the ψ(3770), the radiative transition ψ(3770)→γηc(2S), the ψ(3770) transition to χcJ, isospin violation decay χc0,2→π0ηc, the C−parity violation decays J/ψ→γγ,γϕ are searched for, but no significant signals are observed, and upper limits are set for these decays. The decays of ψ(3770)→γχc1 and J/ψ→π0ϕ signals are observed. These measurements provide more information on the charmonium structure, and the isospin and C-parity violation in the charmonium decays.
分类: 物理学 >> 核物理学 提交时间: 2016-09-10
摘要: Using 2.92 fb−1 of electron-positron annihilation data collected at a center-of-mass energy of s√=3.773 GeV with the BESIII detector, we present an improved measurement of the branching fraction B(D+→ωe+νe)=(1.63±0.11±0.08)×10−3. The parameters defining the corresponding hadronic form factor ratios at zero momentum transfer are determined for the first time, we measure them to be rV=1.24±0.09±0.06 and r2=1.06±0.15±0.05. The first and second uncertainties are statistical and systematic, respectively. We also search for the decay D+→ϕe+νe. An improved upper limit B(D+→ϕe+νe)<1.3×10−5 is set at 90\% confidence level.
分类: 物理学 >> 核物理学 提交时间: 2016-09-10
摘要: Based on a sample of \etapr mesons produced in the radiative decay J/ψ→γη′ in 1.31×109 J/ψ events collected with the BESIII detector, the decay η′→ωe+e− is observed for the first time, with a statistical significance of 8σ. The branching fraction is measured to be B(η′→ωe+e−)=(1.97±0.34(stat)±0.17(syst))×10−4, which is in agreement with theoretical predictions. The branching fraction of η′→ωγ is also measured to be (2.55±0.03(stat)±0.16(syst))×10−2, which is the most precise measurement to date, and the relative branching fraction B(η′→ωe+e−)B(η′→ωγ) is determined to be (7.71±1.34(stat)±0.54(syst))×10−3.
分类: 物理学 >> 核物理学 提交时间: 2016-09-10
摘要: Based on a sample of 1.31×109 J/ψ events collected with the BESIII detector at the BEPCII collider, Dalitz plot analyses of selected 79,625 η→π+π−π0 events, 33,908 η→π0π0π0 events and 1,888 η′→π0π0π0events are performed. The measured matrix elements of η→π+π−π0 are in reasonable agreement with previous measurements. The Dalitz plot slope parameters of η→π0π0π0 and η′→π0π0π0 are determined to be −0.055±0.014±0.004 and −0.640±0.046±0.047, respectively, where the first uncertainties are statistical and the second systematic. Both values are consistent with previous measurements, while the precision of the latter one is improved by a factor of three. Final state interactions are found to have an important role in those decays.