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Institute
The process e+e−→ϕη is studied at 22 center-of-mass energy points (√s) between 2.00 and 3.08 GeV using 715 pb−1 of data collected with the BESIII detector. The measured Born cross section of e+e−→ϕη is found to be consistent with BABAR measurements, but with improved precision. A resonant structure around 2.175 GeV is observed with a significance of 6.9σ with mass (2163.5±6.2±3.0) MeV/c2 and width (31.1+21.1−11.6±1.1) MeV, where the first uncertainties are statistical and the second are systematic.
Based on an 𝑒+𝑒− collision data sample corresponding to an integrated luminosity of 567 pb−1 taken at the center-of-mass energy of √𝑠=4.6 GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay Λ+𝑐→Λ+𝑋 to be ℬ(Λ+𝑐→Λ+𝑋)=(38.2+2.8−2.2±0.9)% using the double-tag method, where 𝑋 refers to any possible final state particles. In addition, we search for direct 𝐶𝑃 violation in the charge asymmetry of this inclusive decay for the first time, and obtain 𝒜𝐶𝑃≡[ℬ(Λ+𝑐→Λ+𝑋)−ℬ(¯Λ−𝑐 → ¯Λ+𝑋)]/[ℬ(Λ+𝑐→Λ+𝑋)+ℬ(¯Λ−𝑐 → ¯Λ+𝑋)]=(2.1+7.0−6.6±1.6)%, a statistically limited result with no evidence of 𝐶𝑃 violation.
We report the first observation of D+→τ+ντ with a significance of 5.1σ. We measure B(D+→τ+ντ)=(1.20±0.24stat.±0.12syst.)×10−3. Taking the world average B(D+→μ+νμ)=(3.74±0.17)×10−4, we obtain Rτ/μ=Γ(D+→τ+ντ)/Γ(D+→μ+νμ)=3.21±0.64stat.±0.43syst., which is consistent with the Standard Model expectation of lepton flavor universality. Using external inputs, our results give values for the D+ decay constant fD+ and the CKM matrix element |Vcd| that are consistent with, but less precise than, other determinations.
Using a data sample of (448.1±2.9)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider, we present measurements of branching fractions for the decays χcJ→Σ+Σ¯− and Σ0Σ¯0. The decays χc1,2→Σ+Σ¯− and Σ0Σ¯0 are observed for the first time, and the branching fractions for χc0→Σ+Σ¯− and Σ0Σ¯0 decays are measured with improved precision. The branching fraction ratios between the charged and neutral modes are consistent with the prediction of isospin symmetry.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 20 times larger than that of χc2→ρ(770)±π∓, which implies the effects are largely due to U-spin symmetry breaking, rather than just isospin symmetry breaking in charmonium decays.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 10 times larger than the upper limit of χc2→ρ(770)±π∓, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 20 times larger than that of χc2→ρ(770)±π∓, which implies the effects are largely due to U-spin symmetry breaking, rather than just isospin symmetry breaking in charmonium decays.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 10 times larger than the upper limit of χc2→ρ(770)±π∓, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.
Using a sample of 1.31×109 J/ψ events collected by the BESIII detector at BEPCII during 2009 and 2012, we study the J/ψ→ωη′π+π− hadronic process. For the first time, we measure the branching ratio B(J/ψ→ωη′π+π−)=(1.12±0.02±0.13)×10−3. We search for the X(1835) state in the η′π+π− invariant mass spectra. No evidence is found and we estimate the upper limit on the branching fraction at 90% confidence level to be B(J/ψ→ωX(1835),X(1835)→η′π+π−)<6.2×10−5.
Several intermediate states of the reaction channels 𝑒+𝑒−→𝜋+𝜋−𝐷0¯𝐷0 and 𝑒+𝑒−→𝜋+𝜋−𝐷+𝐷− are studied using the data samples collected with the BESIII detector at center-of-mass energies above 4.08 GeV. For the first time in this final state, a 𝜓(3770) signal is seen in the 𝐷¯𝐷 invariant mass spectrum, with a statistical significance of 5.2𝜎 at √𝑠=4.42 GeV. There is also evidence for this resonance at √𝑠=4.26 and 4.36 GeV with statistical significance of 3.2𝜎 and 3.3𝜎, respectively. In addition, the Born cross section of 𝑒+𝑒−→𝜋+𝜋−𝜓(3770) is measured. The proposed heavy-quark-spin-symmetry partner of the 𝑋(3872), the state 𝑋2(4013), is also searched for in the 𝐷¯𝐷 invariant mass spectra. No obvious signal is found. The upper limit of the Born cross section of the process 𝑒+𝑒−→𝜌0𝑋2(4013) combined with the branching fraction is measured. Also, the processes 𝑒+𝑒−→𝐷1(2420)¯𝐷+c.c. are investigated. The neutral mode with 𝐷1(2420)0→𝐷0𝜋+𝜋− is reported with statistical significance of 7.4𝜎 at √𝑠=4.42 GeV for the first time, and evidence with statistical significance of 3.2𝜎 and 3.3𝜎 at √𝑠=4.36 and 4.60 GeV is seen, respectively. No evident signal for the process 𝑒+𝑒−→𝐷1(2420)0¯𝐷0+c.c.,𝐷1(2420)0→𝐷*+𝜋− is reported. Evidence for 𝑒+𝑒−→𝐷1(2420)+𝐷−+c.c.,𝐷1(2420)+→𝐷+𝜋+𝜋− is reported with statistical significance of 3.1𝜎 and 3.0𝜎 at √𝑠=4.36 and 4.42 GeV, respectively.