Using a dataset of 6.32 fb−1 of e+e− annihilation data collected with the BESIII detector at center-of-mass energies between 4178 and 4226 MeV, we have measured the absolute branching fraction of the ...leptonic decay Ds+ → τ+ντ via τ+→ e+νe¯ντ , and find BDs+→τ+ντ= ( 5.27 ± 0.10 ± 0.12 ) × 10−2, where the first uncertainty is statistical and the second is systematic. The precision is improved by a factor of 2 compared to the previous best measurement. Combining with fDs+ from lattice quantum chromodynamics calculations or the |Vcs| from the CKMfitter group, we extract | Vcs| = 0.978 ± 0.009 ± 0.012 and fDs+ = ( 251.1 ± 2.4 ± 3.0 ) MeV , respectively. Combining our result with the world averages of BDs+→τ+ντ and BDs+→μ+νμ, we obtain the ratio of the branching fractions BDs+→τ+ντ/BDs+→μ+νμ= 9.72 ± 0.37 , which is consistent with the standard model prediction of lepton flavor universality.
The absolute branching fraction of Λ → pμ−¯νμ is reported for the first time based on an e+ e− annihilation sample of 10 × 109 J/ψ events collected with the BESIII detector at √s = 3.097 GeV. The ...branching fraction is determined to be B(Λ → pμ− νμ) = 1.48 ± 0.21(stat) ± 0.08 (syst) × 10−4, which is improved by about 30% in precision over the previous indirect measurements. Combining this result with the world average of B(Λ → pe−¯νe), we obtain the ratio {Γ(Λ → pμ−¯νμ)/Γ(Λ → pe−¯νe)} to be 0.178 ± 0.028, which agrees with the standard model prediction assuming lepton flavor universality. The asymmetry of the branching fractions of Λ → pμ−¯νμ and ¯Λ → ¯pμ+νμ is also determined, and no evidence for CP violation is found.
We report a study of the processes of ... based on e + e - annihilation samples collected with the BESIII detector operating at BEPCII at five center-of-mass energies ranging from 4.628 to 4.698 GeV ...with a total integrated luminosity of 3.7 fb-1. An excess of events over the known contributions of the conventional charmed mesons is observed near the ... mass thresholds in the K+ recoil-mass spectrum for events collected ... The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as ... , respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3 σ over the contributions only from the conventional charmed mesons. This is the first candidate for a charged hidden-charm tetraquark with strangeness, decaying into ... . However, the properties of the excess need further exploration with more statistics. (ProQuest: ... denotes formulae omitted.)
We report the most precise measurements to date of the strong-phase parameters between D0 and D0 decays to K0S,L π+ π− using a sample of 2.93 fb −1 of e+e− annihilation data collected at a ...center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider. Our results provide the key inputs for a binned model-independent determination of the Cabibbo-Kobayashi-Maskawa angle γ/ϕ3 with B decays. Using our results, the decay model sensitivity to the γ/ϕ3 measurement is expected to be between 0.7° and 1.2°, approximately a factor of three smaller than that achievable with previous measurements, based on the studies of the simulated data. The improved precision of this work ensures that measurements of γ/ϕ3 will not be limited by knowledge of strong phases for the next decade. Furthermore, our results provide critical input for other flavor-physics investigations, including charm mixing, other measurements of C P violation, and the measurement of strong-phase parameters for other D -decay modes.
A partial-wave analysis is performed for the process e + e − → K + K − π0π0 at the center-of-mass energies ranging from 2.000 to 2.644 GeV. The data samples of e + e − collisions, collected by the ...BESIII detector at the BEPCII collider with a total integrated luminosity of 300 pb−1 , are analyzed. The total Born cross sections for the process e + e − → K + K − π0π0 , as well as the Born cross sections for the subprocesses e + e − → ϕ π0π0 , K + ( 1460 ) K − , K + 1 ( 1400 ) K − , K + 1 ( 1270 ) K − , and K * + ( 892 ) K * − ( 892 ) , are measured versus the center-of-mass energy. The corresponding results for e + e − → K + K − π0π0 and ϕ π0π0 are consistent with those of BABAR with better precision. By analyzing the cross sections for the four subprocesses, K + ( 1460 ) K − , K + 1 ( 1400 ) K − , K + 1 ( 1270 ) K − , and K * + ( 892 ) K * − ( 892 ) , a structure with mass M = ( 2126.5 ± 16.8 ± 12.4 ) MeV / c 2 and width Γ = ( 106.9 ± 32.1 ± 28.1 ) MeV is observed with an overall statistical significance of 6.3 σ , although with very limited significance in the subprocesses e + e − → K + 1 ( 1270 ) K − and K * + ( 892 ) K * − ( 892 ) . The resonant parameters of the observed structure suggest it can be identified with the ϕ ( 2170 ) , thus the results provide valuable input to the internal nature of the ϕ ( 2170 ) .
By analyzing a 2.93 fb−1 data sample of e+e− collisions, recorded at a center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we report the first observation of ...the semileptonic D+ transition into the axial-vector meson D+ → ¯K1(1270)0 e+νe with a statistical significance greater than 10σ. Its decay branching fraction is determined to be BD+ → ¯K1(1270)0 e+νe = (2.30 ± 0.26+0.18−0.21 ± 0.25) × 10−3, where the first and second uncertainties are statistical and systematic, respectively, and the third originates from the input branching fraction of ¯K1(1270)0 → K−π+π0.
Using a 3.19 fb−1 data sample collected at an e+e− center-of-mass energy of Ecm = 4.178 GeV with the BESIII detector, we measure the branching fraction of the leptonic decay D+s → μ+νμ to be BD+s → ...μ+νμ = (5.49 ± 0.16stat ± 0.15syst) × 10−3. Combining our branching fraction with the masses of the D+s and μ+ and the lifetime of the D+s, we determine fD+s|Vcs| = 246.2 ± 3.6stat ± 3.5syst MeV. Using the c → s quark mixing matrix element |Vcs| determined from a global standard model fit, we evaluate the D+s decay constant fD+s = 252.9 ± 3.7stat ± 3.6syst MeV. Alternatively, using the value of fD+s calculated by lattice quantum chromodynamics, we find |Vcs| = 0.985 ± 0.014stat ± 0.014syst. These values of BD+s → μ+νμ, fD+s|Vcs|, fD+s and |Vcs| are each the most precise results to date.
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