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Using e+e− annihilation data corresponding to a total integrated luminosity of 6.32 fb−1 collected at center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay D+s→K0SK0Sπ+ for the first time. An enhancement is observed in the K0SK0S mass spectrum near 1.7 GeV/c2, which was not seen in D+s→K+K−π+ in an earlier work, implying the existence of an isospin one partner of the f0(1710). The branching fraction of the decay D+s→K0SK0Sπ+ is determined to be B(D+s→K0SK0Sπ+)=(0.68±0.04stat±0.01syst)%.
he Born cross sections for the process 𝑒+𝑒−→𝜂′𝜋+𝜋− at different center-of-mass energies between 2.00 and 3.08 GeV are reported with improved precision from an analysis of data samples collected with the BESIII detector operating at the BEPCII storage ring. An obvious structure is observed in the Born cross section line shape. Fit as a Breit-Wigner resonance, it has a statistical significance of 6.3𝜎 and a mass and width of 𝑀=(2111±43±25) MeV/𝑐2 and Γ=(135±34±30) MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in 𝑒+𝑒−→𝜂′𝜋+𝜋− and BESIII in 𝑒+𝑒−→𝜔𝜋0 within two standard deviations.
Observation of a near-threshold structure in the K⁺ recoil-mass spectra in e⁺e⁻ → K⁺(Dₛ⁻D*⁰+Dₛ*⁻D⁰)
(2021)
We report a study of the processes of 𝑒+𝑒−→𝐾+𝐷−𝑠𝐷*0 and 𝐾+𝐷*−𝑠𝐷0 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 𝐷−𝑠𝐷*0 and 𝐷*−𝑠𝐷0 mass thresholds in the 𝐾+ recoil-mass spectrum for events collected at √𝑠=4.681 GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5+1.8
−2.6±2.1) MeV/𝑐2 and (12.8+5.3−4.4±3.0) MeV, 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 𝐷−𝑠𝐷*0 and 𝐷*−𝑠𝐷0. However, the properties of the excess need further exploration with more statistics.
Using 2.93 fb−1 of 𝑒+𝑒− collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the absolute branching fractions of 14 hadronic 𝐷0(+) decays to exclusive final states with an 𝜂, e.g., 𝐷0→𝐾−𝜋+𝜂, 𝐾0𝑆𝜋0𝜂, 𝐾+𝐾−𝜂, 𝐾0𝑆𝐾0𝑆𝜂, 𝐾−𝜋+𝜋0𝜂, 𝐾0𝑆𝜋+𝜋−𝜂, 𝐾0𝑆𝜋0𝜋0𝜂, and 𝜋+𝜋−𝜋0𝜂; 𝐷+→𝐾0𝑆𝜋+𝜂, 𝐾0𝑆𝐾+𝜂, 𝐾−𝜋+𝜋+𝜂, 𝐾0𝑆𝜋+𝜋0𝜂, 𝜋+𝜋+𝜋−𝜂, and 𝜋+𝜋0𝜋0𝜂. Among these decays, the 𝐷0→𝐾−𝜋+𝜂 and 𝐷+→𝐾0 𝑆𝜋+𝜂 decays have the largest branching fractions, which are ℬ(𝐷0→𝐾−𝜋+𝜂) = (1.853±0.025stat±0.031syst)% and ℬ(𝐷+→𝐾0𝑆𝜋+𝜂) = (1.309±0.037stat±0.031syst)%, respectively. The charge-parity asymmetries for the six decays with highest event yields are determined, and no statistically significant charge-parity violation is found.
Using a total of 5.25 fb−1 of e+e− collision data with center-of-mass energies from 4.236 to 4.600 GeV, we report the first observation of the process e+e− → ηψ(2S) with a statistical significance of 4.9 standard deviations. The data sets were collected by the BESIII detector operating at the BEPCII storage ring. We measure the yield of events integrated over center-of-mass energies and also present the energy dependence of the measured cross section.
Search for the lepton number violating decay Σ⁻ → pe⁻e⁻ and the rare inclusive decay Σ⁻ → Σ⁺X
(2021)
Using a data sample of (1310.6±7.0)×106 𝐽/𝜓 events taken with the BESIII detector at the center-of-mass energy of 3.097 GeV, we search for the first time for the lepton number violating decay Σ−→𝑝𝑒−𝑒− and the rare inclusive decay Σ−→Σ+𝑋, where 𝑋 denotes any possible particle combination. The Σ− candidates are tagged in 𝐽/𝜓→¯Σ(1385)+Σ− decays. No signal candidates are found, and the upper limits on the branching fractions at the 90% confidence level are determined to be ℬ(Σ−→𝑝𝑒−𝑒−)<6.7×10−5 and ℬ(Σ−→Σ+𝑋)<1.2×10−4.
Using 2.93 fb−1 of 𝑒+𝑒− annihilation data collected at a center-of-mass energy √𝑠=3.773 GeV with the BESIII detector operating at the BEPCII collider, we search for the semileptonic 𝐷0(+) decays into a 𝑏1(1235)−(0) axial-vector meson for the first time. No significant signal is observed for either charge combination. The upper limits on the product branching fractions are ℬ𝐷0→𝑏1(1235)−𝑒+𝜈𝑒·ℬ𝑏1(1235) −→ 𝜔𝜋−<1.12×10−4 and ℬ𝐷+→𝑏1(1235)0𝑒+𝜈𝑒·ℬ𝑏1(1235)0→𝜔𝜋0<1.75×10−4 at the 90% confidence level.
Using 2.93 fb−1 of 𝑒+𝑒− collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the first observation of the doubly Cabibbo-suppressed decay 𝐷+→𝐾+𝜋+𝜋−𝜋0 is reported. After removing decays that contain narrow intermediate resonances, including 𝐷+→𝐾+𝜂, 𝐷+→𝐾+𝜔, and 𝐷+→𝐾+𝜙, the branching fraction of the decay 𝐷+→𝐾+𝜋+𝜋−𝜋0 is measured to be (1.13±0.08stat±0.03syst)×10−3. The ratio of branching fractions of 𝐷+→𝐾+𝜋+𝜋−𝜋0 over 𝐷+→𝐾−𝜋+𝜋+𝜋0 is found to be (1.81±0.15)%, which corresponds to (6.28±0.52)tan4𝜃𝐶, where 𝜃𝐶 is the Cabibbo mixing angle. This ratio is significantly larger than the corresponding ratios for other doubly Cabibbo-suppressed decays. The asymmetry of the branching fractions of charge-conjugated decays 𝐷±→𝐾±𝜋±𝜋∓𝜋0 is also determined, and no evidence for 𝐶𝑃 violation is found. In addition, the first evidence for the 𝐷+→𝐾+𝜔 decay, with a statistical significance of 3.3𝜎, is presented and the branching fraction is measured to be ℬ(𝐷+→𝐾+𝜔) = (5.7+2.5−2.1stat±0.2syst)×10−5.
The processes 𝑒+𝑒−→𝐷+ 𝑠𝐷𝑠1(2460)−+c.c. and 𝑒+𝑒−→𝐷*+ 𝑠𝐷𝑠1(2460)−+c.c. are studied for the first time using data samples collected with the BESIII detector at the BEPCII collider. The Born cross sections of 𝑒+𝑒−→𝐷+ 𝑠𝐷𝑠1(2460)−+c.c. at nine center-of-mass energies between 4.467 GeV and 4.600 GeV and those of 𝑒+𝑒−→𝐷*+ 𝑠𝐷𝑠1(2460)−+c.c. at √𝑠=4.590 GeV and 4.600 GeV are measured. No obvious charmonium or charmoniumlike structure is seen in the measured cross sections.
By analyzing a data sample corresponding to an integrated luminosity of 2.93 fb−1 collected at a center-of-mass energy of 3.773 GeV with By analyzing a data sample corresponding to an integrated luminosity of 2.93 fb−1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure for the first time the absolute branching fraction of the 𝐷+→𝜂𝜇+𝜈𝜇 decay to be ℬ𝐷+→𝜂𝜇+𝜈𝜇=(10.4±1.0stat±0.5syst)×10−4. Using the world averaged value of ℬ𝐷+→𝜂𝑒+𝜈𝑒, the ratio of the two branching fractions is determined to be ℬ𝐷+→𝜂𝜇+𝜈𝜇/ℬ𝐷+→𝜂𝑒+𝜈𝑒=0.91±0.13(stat+syst), which agrees with the theoretical expectation of lepton flavor universality within uncertainty. By studying the differential decay rates in five four-momentum transfer intervals, we obtain the product of the hadronic form factor 𝑓𝜂+(0) and the 𝑐→𝑑 Cabibbo-Kobayashi-Maskawa matrix element |𝑉𝑐𝑑| to be 𝑓𝜂+(0)|𝑉𝑐𝑑|=0.087±0.008stat±0.002syst. Taking the input of |𝑉𝑐𝑑| from the global fit in the standard model, we determine 𝑓𝜂+(0)=0.39±0.04stat±0.01syst. On the other hand, using the value of 𝑓𝜂+(0) calculated in theory, we find |𝑉𝑐𝑑| = 0.242±0.022stat±0.006syst±0.033theory.