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This paper reports the study of D+s→τ+ν via τ+→π+ν¯τ using a boosted decision tree method, with 7.33 fb−1 of e+e− collision data collected by the BESIII detector at center-of-mass energies between 4.128 and 4.226~GeV. The branching fraction of D+s→τ+ντ is determined to be (5.44±0.17stat±0.13syst)%. The product of the D+s decay constant fD+s and the CKM matrix element |Vcs| is fD+s|Vcs| =(248.3±3.9stat±3.1syst±1.0input) MeV. Combining with the |Vcs| value obtained from the Standard Model global fit or the fD+s from the lattice quantum chromodynamics, we determine |Vcs| = 0.993±0.015stat±0.012syst±0.004input and fD+s =(255.0±4.0stat±3.2syst±1.0input) MeV. The first uncertainty is statistical, the second one is systematic and the third one is due to the input parameters, mainly the lifetime of D+s. All results obtained in this work supersede the BESIII previous results based on 6.32 fb−1 of e+e− collision data taken at center-of-mass energies between 4.178 and 4.226~GeV.
Precise measurement of the branching fractions of of J/ψ → Λ¯π⁺Σ⁻ + c.c. and J/ψ → Λ¯π⁻Σ⁺ + c.c.
(2023)
Based on a data sample of (10087±44)×106 J/ψ events collected with the BESIII detector, the branching fraction of J/ψ→Λ¯π+Σ−+c.c. is measured to be (1.221±0.002±0.038)×10−3, and the branching fraction of its isospin partner mode J/ψ→Λ¯π−Σ++c.c. is measured to be (1.244±0.002±0.045)×10−3 with improved precision. Here the first uncertainties are statistical and the second ones systematic. The isospin symmetry of the Σ baryon in charmonium hadronic decay and the "12% rule" are tested, and no violation is found. The potential of using these channels as Σ baryon sources for nuclear physics research is studied, and the momentum and angular distributions of these sources are provided.
A light scalar X0 or vector X1 particles have been introduced as a possible explanation for the (g−2)μ anomaly and dark matter phenomena.
Using (8.998±0.039)×109 $\jpsi$ events collected by the BESIII detector, we search for a light muon philic scalar X0 or vector X1 in the processes J/ψ→μ+μ−X0,1 with X0,1 invisible decays. No obvious signal is found, and the upper limits on the coupling g′0,1 between the muon and the X0,1 particles are set to be between 1.1×10−3 and 1.0×10−2 for the X0,1 mass in the range of 1<M(X0,1)<1000 MeV/c2 at 90% confidence level.
By analyzing 7.33 fb−1 of e+e− annihilation data collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector, we report the observation of the semileptonic decay D+s→η′μ+νμ, with a statistical significance larger than 10σ, and the measurements of the D+s→ημ+νμ and D+s→η′μ+νμ decay dynamics for the first time. The branching fractions of D+s→ημ+νμ and D+s→η′μ+νμ are determined to be (2.235±0.051stat±0.052syst)% and (0.801±0.055stat±0.028syst)%, respectively, with precision improved by factors of 6.0 and 6.6 compared to the previous best measurements. Combined with the results for the decays D+s→ηe+νe and D+s→η′e+νe, the ratios of the decay widths are examined both inclusively and in several ℓ+νℓ four-momentum transfer ranges. No evidence for lepton flavor universality violation is found within the current statistics. The products of the hadronic form factors fη(′)+,0(0) and the c→s Cabibbo-Kobayashi-Maskawa matrix element |Vcs| are determined. The results based on the two-parameter series expansion are fη+,0(0)|Vcs| = 0.452±0.010stat±0.007syst and fη′+,0(0)|Vcs| = 0.504±0.037stat±0.012syst, which help to constrain present models on fη(′)+,0(0). The forward-backward asymmetries are determined to be ⟨AηFB⟩=−0.059±0.031stat±0.005syst and ⟨Aη′FB⟩=−0.064±0.079stat±0.006syst for the first time, which are consistent with the theoretical calculation.
A search for the rare radiative leptonic decay D+s→γe+νe is performed for the first time using electron-positron collision data corresponding to an integrated luminosity of 3.19 fb−1, collected with the BESIII detector at a center-of-mass energy of 4.178 GeV. No evidence for the D+s→γe+νe decay is seen and an upper limit of B(D+s→γe+νe)<1.3×10−4 is set on the partial branching fraction at a 90\% confidence level for radiative photon energies E∗γ>0.01~GeV.
Using a sample of (10.09±0.04)×109 J/ψ events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay J/ψ→γηη′ is performed. The first observation of an isoscalar state with exotic quantum numbers JPC=1−+, denoted as η1(1855), is reported in the process J/ψ→γη1(1855) with η1(1855)→ηη′. Its mass and width are measured to be (1855±9+6−1)MeV/c2 and (188±18+3−8)MeV, respectively, where the first uncertainties are statistical and the second are systematic, and its statistical significance is estimated to be larger than 19σ.
Using a data sample corresponding to an integrated luminosity of 10.9 fb−1 collected at center-of-mass energies from 4.16 to 4.34 GeV with the BESIII detector, we search for the decay χc1(3872)→π+π−χc1 in the radiative production e+e−→γχc1(3872). No significant signal is observed, and the ratio for the branching fraction of χc1(3872)→π+π−χc1 to χc1(3872)→π+π−J/ψ is measured as R≡B[χc1(3872)→π+π−χc1]B[χc1(3872)→π+π−J/ψ]<0.18 at 90% confidence level. The upper limit on the product of the cross section σ[e+e−→γχc1(3872)] and the branching fraction B[χc1(3872)→π+π−χc1] at each center-of-mass energy is also given. These measurements favor the non-conventional charmonium nature of the χc1(3872) state.
Using 𝑒+𝑒− collision data corresponding to an integrated luminosity of 7.33 fb−1 recorded by the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, we present an analysis of the decay 𝐷+𝑠→𝜋+𝜋−𝑒+𝜈𝑒, where the 𝐷+𝑠 is produced via the process 𝑒+𝑒−→𝐷*±𝑠𝐷∓𝑠. We observe the 𝑓0(980) in the 𝜋+𝜋− system and the branching fraction of the decay 𝐷+𝑠→𝑓0(980)𝑒+𝜈𝑒 with 𝑓0(980)→𝜋+𝜋− measured to be (1.72±0.13stat±0.10syst)×10−3, where the uncertainties are statistical and systematic, respectively. The dynamics of the 𝐷+𝑠→𝑓0(980)𝑒+𝜈𝑒 decay are studied with the simple pole parametrization of the hadronic form factor and the Flatté formula describing the 𝑓0(980) in the differential decay rate, and the product of the form factor 𝑓𝑓0+(0) and the 𝑐→𝑠 Cabibbo-Kobayashi-Maskawa matrix element |𝑉𝑐𝑠| is determined for the first time to be 𝑓𝑓0+(0)|𝑉𝑐𝑠|=0.504±0.017stat±0.035syst. Furthermore, the decay 𝐷+
𝑠→𝑓0(500)𝑒+𝜈𝑒 is searched for the first time but no signal is found. The upper limit on the branching fraction of 𝐷+𝑠→𝑓0(500)𝑒+𝜈𝑒, 𝑓0(500)→𝜋+𝜋− decay is set to be 3.3×10−4 at 90% confidence level.
The processes hc→γP(P=η′, η, π0) are studied with a sample of (27.12±0.14)×108 ψ(3686) events collected by the BESIII detector at the BEPCII collider. The decay hc→γη is observed for the first time with the significance of 9.0σ, and the branching fraction is determined to be (3.77±0.55±0.13±0.26)×10−4, while B(hc→γη′) is measured to be (1.40±0.11±0.04±0.10)×10−3, where the first uncertainties are statistical, the second systematic, and the third from the branching fraction of ψ(3686)→π0hc. The combination of these results allows for a precise determination of Rhc=B(hc→γη)B(hc→γη′), which is calculated to be (27.0±4.4±1.0)%. The results are valuable for gaining a deeper understanding of η−η′ mixing, and its manifestation within quantum chromodynamics. No significant signal is found for the decay hc→γπ0, and an upper limit is placed on its branching fraction of B(hc→γπ0)<5.0×10−5, at the 90% confidence level.