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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.
We search for an axion-like particle (ALP) a through the process ψ(3686)→π+π−J/ψ, J/ψ→γa, a→γγ in a data sample of (2.71±0.01)×109 ψ(3686) events collected by the BESIII detector. No significant ALP signal is observed over the expected background, and the upper limits on the branching fraction of the decay J/ψ→γa and the ALP-photon coupling constant gaγγ are set at 95% confidence level in the mass range of 0.165≤ma≤2.84GeV/c2. The limits on B(J/ψ→γa) range from 8.3×10−8 to 1.8×10−6 over the search region, and the constraints on the ALP-photon coupling are the most stringent to date for 0.165≤ma≤1.468GeV/c2.
Relative fractions and phases of the intermediate decays are determined. With the detection efficiency estimated by the results of the amplitude analysis, the branching fraction of Dþ s → K−Kþπþπ0 decay is measured to be ð5.42 0.10stat 0.17systÞ%.
By analyzing an electron-positron collision data sample corresponding to an integrated luminosity of 2.93 fb−1 taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, we obtain for the first time the absolute branching fractions for seven 𝐷0 and 𝐷+ hadronic decay modes and search for the hadronic decay 𝐷0→𝐾0𝑆𝐾0𝑆𝜋0 with much improved sensitivity. The results are ℬ(𝐷0→𝐾0𝑆𝜋0𝜋0𝜋0)=(7.64±0.30±0.29)×10−3, (𝐷0→𝐾−𝜋+𝜋0𝜋0𝜋0)=9.54±0.30±0.31)×10−3, ℬ(𝐷0→𝐾0𝑆𝜋+𝜋−𝜋0𝜋0)=(12.66±0.45±0.43)×10−3, ℬ(𝐷+→𝐾0𝑆𝜋+𝜋0𝜋0)=(29.04±0.62±0.87)×10−3, ℬ(𝐷+→𝐾0𝑆𝜋+𝜋+𝜋−𝜋0)=(15.28±0.57±0.60)×10−3, ℬ(𝐷+→𝐾0𝑆𝜋+𝜋0𝜋0𝜋0)=(5.54±0.44±0.32)×10−3, ℬ(𝐷+→𝐾−𝜋+𝜋+𝜋0𝜋0)=(4.95±0.26±0.19)×10−3, and ℬ(𝐷0→𝐾0𝑆𝐾0𝑆𝜋0)<1.45×10−4 at the 90% confidence level. Here, the first uncertainties are statistical, and the second ones are systematic. The newly studied decays greatly enrich the knowledge of the 𝐷→¯𝐾𝜋𝜋𝜋 and 𝐷→¯𝐾𝜋𝜋𝜋𝜋 hadronic decays and open a bridge to access more two-body hadronic 𝐷 decays containing scalar, vector, axial, and tensor mesons in the charm sector.
The process 𝑒+𝑒−→𝜙𝜂′ has been studied for the first time in detail using data sample collected with the BESIII detector at the BEPCII collider at center of mass energies from 2.05 to 3.08 GeV. A resonance with quantum numbers 𝐽𝑃𝐶=1−− is observed with mass 𝑀=(2177.5±4.8(stat)±19.5(syst))MeV/𝑐2 and width Γ=(149.0±15.6(stat)±8.9(syst)) MeV with a statistical significance larger than 10𝜎, including systematic uncertainties. If the observed structure is identified with the 𝜙(2170), then the ratio of partial width between the 𝜙𝜂′ by BESIII and 𝜙𝜂 by BABAR is (ℬ𝑅𝜙𝜂Γ𝑅𝑒𝑒)/(ℬ𝑅𝜙𝜂′Γ𝑅𝑒𝑒)=0.23±0.10(stat)±0.18(syst), which is smaller than the prediction of the 𝑠¯𝑠𝑔 hybrid models by several orders of magnitude.
The Born cross sections and effective form factors for process 𝑒+𝑒−→Ξ−¯Ξ+ are measured at eight center-of-mass energies between 2.644 and 3.080 GeV, using a total integrated luminosity of 363.9 pb−1 𝑒+𝑒− collision data collected with the BESIII detector at BEPCII. After performing a fit to the Born cross section of 𝑒+𝑒−→Ξ−¯Ξ+, no significant threshold effect is observed.
We report on the first search for ¯Λ−Λ oscillations in the decay 𝐽/𝜓→𝑝𝐾−¯Λ+c.c. by analyzing 1.31×109 𝐽/𝜓 events accumulated with the BESIII detector at the BEPCII collider. The 𝐽/𝜓 events are produced using 𝑒+𝑒− collisions at a center of mass energy √𝑠=3.097 GeV. No evidence for hyperon oscillations is observed. The upper limit for the oscillation rate of ¯Λ to Λ hyperons is determined to be 𝒫(Λ)=[ℬ(𝐽/𝜓→𝑝𝐾−Λ+c.c.)/ℬ(𝐽/𝜓→𝑝𝐾−¯Λ+c.c.)]<4.4×10−6 corresponding to an oscillation parameter 𝛿𝑚Λ¯Λ of less than 3.8×10−18 GeV at the 90% confidence level.
Using 10.1 × 109 J/ψ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy √s = 3.097 GeV and collected with the BESIII detector, we present a search for the rare semi-leptonic decay J/ψ → D−e+νe + c.c. No excess of signal above background is observed, and an upper limit on the branching fraction ℬ(J/ψ → D−e+νe + c. c.) < 7.1 × 10−8 is obtained at 90% confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.
Using 448.1 × 106 ψ(3686) decays collected with the BESIII detector at the BEPCII e+e− storage rings, the branching fractions and angular distributions of the decays χcJ → Ξ−Ξ¯¯¯¯+ and Ξ0Ξ¯¯¯¯0 (J = 0, 1, 2) are measured based on a partial-reconstruction technique. The decays χc1 → Ξ0Ξ¯¯¯¯0 and χc2 → Ξ0Ξ¯¯¯¯0 are observed for the first time with statistical significances of 7σ and 15σ, respectively. The results of this analysis are in good agreement with previous measurements and have significantly improved precision.
The 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=(2108±46±25)~MeV/c2 and Γ=(138±36±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.