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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.
We report a study of the processes of e+e−→K+(D−sD∗0+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 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 of the 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.
We report the first measurements of the absolute branching fractions of D0 → K0 Lϕ, D0 → K0Lη, D0 → K0Lω, and D0 → K0Lη0, by analyzing 2.93 fb−1 of eþe− collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector. Taking the world averages of the branching fractions of D0 → K0Sϕ, D0 → K0Sη, D0 → K0Sω, and D0 → K0Sη0, the K0S − K0L asymmetries RðD0; XÞ in these decay modes are obtained. The CP asymmetries in these decays are also determined. No significant CP violation is observed
Observation of resonance structures in e⁺e⁻ → π⁺π⁻ψ₂(3823) and mass measurement of ψ₂(3823)
(2022)
Using a data sample corresponding to an integrated luminosity of 11.3 fb−1 collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we measure the product of the 𝑒+𝑒−→𝜋+𝜋−𝜓2(3823) cross section and the branching fraction ℬ[𝜓2(3823)→𝛾𝜒𝑐1]. For the first time, resonance structure is observed in the cross section line shape of 𝑒+𝑒−→𝜋+𝜋−𝜓2(3823) with significances exceeding 5𝜎. A fit to data with two coherent Breit-Wigner resonances modeling the √𝑠-dependent cross section yields 𝑀(𝑅1)=4406.9±17.2±4.5 MeV/𝑐2, Γ(𝑅1)=128.1±37.2±2.3 MeV, and 𝑀(𝑅2)=4647.9±8.6±0.8 MeV/𝑐2, Γ(𝑅2)=33.1±18.6±4.1 MeV. Though weakly disfavored by the data, a single resonance with 𝑀(𝑅)=4417.5±26.2±3.5 MeV/𝑐2, Γ(𝑅)=245±48±13 MeV is also possible to interpret data. This observation deepens our understanding of the nature of the vector charmoniumlike states. The mass of the 𝜓2(3823) state is measured as (3823.12±0.43±0.13) MeV/𝑐2, which is the most precise measurement to date.
The integrated luminosities of data samples collected in the BESIII experiment in 2016–2017 at center-of-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events. The integrated luminosities of old datasets collected in 2010–2014 are updated by considering corrections related to detector performance, offsetting the effect of newly discovered readout errors in the electromagnetic calorimeter, which can haphazardly occur.
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.
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.
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.
Using a sample of 1.31×109 𝐽/𝜓 events collected with the BESIII detector, we perform a study of 𝐽/𝜓→𝛾𝜂𝜂𝜂′ to search for the 𝑋(2370) and 𝜂𝑐 in the 𝜂𝜂𝜂′ invariant mass distribution. No significant signal for the 𝑋(2370) is observed, and we set an upper limit for the product branching fraction of ℬ(𝐽/𝜓→𝛾𝑋(2370)·ℬ(𝑋(2370)→𝜂𝜂𝜂′)<9.2×10−6 at the 90% confidence level. A clear 𝜂𝑐 signal is observed for the first time, yielding a product branching fraction of ℬ(𝐽/𝜓→𝛾𝜂𝑐)·ℬ(𝜂𝑐→𝜂𝜂𝜂′)=(4.86±0.62(stat)±0.45(sys))×10−5.