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A search has been performed for the semileptonic decays D0→K0SK−e+νe, D+→K0SK0Se+νe and D+→K+K−e+νe, using 7.9 fb−1 of e+e− annihilation data collected at the center-of-mass energy s√=3.773 GeV by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits are set at the 90\% confidence level of 2.13×10−5, 1.54×10−5 and 2.10×10−5 for the branching fractions of D0→K0SK−e+νe, D+→K0SK0Se+νe and D+→K+K−e+νe, respectively.
We perform a study of the X(3872) lineshape using the data samples of e+e−→γX(3872), X(3872)→D0D¯0π0 and π+π−J/ψ collected with the BESIII detector. The effects of the coupled-channels and the off-shell D∗0 are included in the parameterization of the lineshape. The lineshape mass parameter is obtained to be MX=(3871.63±0.13+0.06−0.05) MeV. Two poles are found on the first and second Riemann sheets corresponding to the D∗0D¯0 branch cut. The pole location on the first sheet is much closer to the D∗0D¯0 threshold than the other, and is determined to be 7.04±0.15+0.07−0.08 MeV above the D0D¯0π0 threshold with an imaginary part −0.19±0.08+0.14−0.19 MeV.
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.
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 massless particle beyond the Standard Model is searched for in the two-body decay Σ+→p+invisible using (1.0087±0.0044)×1010 J/ψ events collected at a center-of-mass energy of s√=3.097 GeV with the BESIII detector at the BEPCII collider. No significant signal is observed, and the upper limit on the branching fraction B(Σ+→p+invisible) is determined to be 3.2×10−5 at the 90% confidence level. This is the first search for a flavor-changing neutral current process with missing energy in hyperon decays which plays an important role in constraining new physics models.
We report the measurement of the inclusive cross sections for e+e−→nOCH (where nOCH denotes non-open charm hadrons) with improved precision at center-of-mass (c.m.) energies from 3.645 to 3.871 GeV. We observe three resonances: R(3760), R(3780), and R(3810) with significances of 8.1σ, 13.7σ, and 8.8σ, respectively. The R(3810) state is observed for the first time, while the R(3760) and R(3780) states are observed for the first time in the nOCH cross sections. Two sets of resonance parameters describe the energy-dependent line shape of the cross sections well. In set I [set II], the R(3810) state has mass (3805.7±1.1±2.7) [(3805.7±1.1±2.7)] MeV/c2, total width (11.6±2.9±1.9) [(11.5±2.8±1.9)] MeV, and an electronic width multiplied by the nOCH decay branching fraction of (10.9±3.8±2.5) [(11.0±3.4±2.5)] eV. In addition, we measure the branching fractions B[R(3760)→nOCH]=(25.2±16.1±30.4)%[(6.4±4.8±7.7)%] and B[R(3780)→nOCH]=(12.3±6.6±8.3)%[(10.4±4.8±7.0)%] for the first time. The R(3760) state can be interpreted as an open-charm (OC) molecular state, but containing a simple four-quark state component. The R(3810) state can be interpreted as a hadrocharmonium state.
We report the measurement of the cross sections for e+e−→{nOCH} (nOCH stands for non-open charm hadrons) with improved precision at center-of-mass energies from 3.645 to 3.871 GeV. We observe for the first time a three-resonance structure in the energy-dependent lineshape of the cross sections, which are R(3760), R(3780) and R(3810) with significances of 9.4σ, 15.7σ, and 9.8σ, respectively. The R(3810) is observed for the first time. We found two solutions in analysis of the cross sections. For solution I [solution II], we measure the mass, the total width and the product of electronic width and nOCH decay branching fraction to be (3805.8±1.1±2.7) [(3805.8±1.1±2.7)] MeV/c2, (11.6±2.6±1.9) [(11.5±2.5±1.8)] MeV, and (10.8±3.2±2.3) [(11.0±2.9±2.4)] eV for the R(3810), respectively. In addition, we measure the branching fractions B(R(3760)→{nOCH})=(24.5±13.4±27.4)%[(6.8±5.4±7.6)%] for the first time, and B(R(3780)→{nOCH})=(11.6±5.8±7.8)%[(10.3±4.5±6.9)%]. Moreover, we determine the open-charm (OC) branching fraction B(R(3760)→{OC})=(75.5±13.4±27.4)%[(93.2±5.4±7.6)%], which supports the interpretation of R(3760) as an OC pair molecular state, but contained a simple four-quark state component. The first uncertainties are from fits to the cross sections, and the second are systematic.
By analyzing e+e− annihilation data corresponding to an integrated luminosity of 7.93 fb−1, collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we search for the semileptonic decays D0→K−ηe+νe, D+→K0Sηe+νe and D+→ηηe+νe for the first time. We present evidence for D0→K−ηe+νe with a significance of 3.3σ. The branching fraction of D0→K−ηe+νe is measured to be (0.84+0.29−0.34±0.22)×10−4. Here, the first uncertainties are statistical and the second ones are systematic. No significant signals are observed for the decays D+→K0Sηe+νe and D+→ηηe+νe and we set the upper limits on their branching fractions.
The process e+e−→D∗+sD∗−s is studied with a semi-inclusive method using data samples at center-of-mass energies from threshold to 4.95 GeV collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections of the process are measured for the first time with high precision in this energy region. Two resonance structures are observed in the energy-dependent cross sections around 4.2 and 4.4 GeV. By fitting the cross sections with a coherent sum of three Breit-Wigner amplitudes and one phase-space amplitude, the two significant structures are assigned masses of (4186.5±9.0±30) MeV/c2 and (4414.5±3.2±6.0) MeV/c2, widths of (55±17±53) MeV and (122.6±7.0±8.2) MeV, where the first errors are statistical and the second ones are systematic. The inclusion of a third Breit-Wigner amplitude is necessary to describe a structure around 4.79 GeV.
Using e+e− collision data corresponding to a total integrated luminosity of 12.9 fb−1 collected with the BESIII detector at the BEPCII collider, the exclusive Born cross sections and the effective form factors of the reaction e+e−→Ξ−Ξ¯+ are measured via the single baryon-tag method at 23 center-of-mass energies between 3.510 and 4.843 GeV. Evidence for the decay ψ(3770)→Ξ−Ξ¯+ is observed with a significance of 4.5σ by analyzing the measured cross sections together with earlier BESIII results. For the other charmonium(-like) states ψ(4040), ψ(4160), Y(4230), Y(4360), ψ(4415), and Y(4660), no significant signal of their decay to Ξ−Ξ¯+ is found. For these states, upper limits of the products of the branching fraction and the electronic partial width at the 90% confidence level are provided.
The process e+e−→D∗+sD∗−s is studied with a semi-inclusive method using data samples at center-of-mass energies from threshold to 4.95 GeV collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections of the process are measured for the first time with high precision in this energy region. Two resonance structures are observed in the energy-dependent cross sections around 4.2 and 4.4 GeV. By fitting the cross sections with a coherent sum of three Breit-Wigner amplitudes and one phase-space amplitude, the two significant structures are assigned masses of (4186.5±9.0±30) MeV/c2 and (4414.5±3.2±6.0) MeV/c2, widths of (55±17±53) MeV and (122.6±7.0±8.2) MeV, where the first errors are statistical and the second ones are systematic. The inclusion of a third Breit-Wigner amplitude is necessary to describe a structure around 4.79 GeV.
The CP-even fractions (F+) of the decays D0→π+π−π0 and D0→K+K−π0 are measured with a quantum-correlated ψ(3770)→DD¯ data sample collected by the BESIII experiment corresponding to an integrated luminosity of 7.93 fb−1. The results are Fπ+π−π0+=0.9406±0.0036±0.0021 and FK+K−π0+=0.631±0.014±0.011, where the first uncertainties are statistical and the second systematic. These measurements are consistent with the previous determinations, and the uncertainties for Fπ+π−π0+ and FK+K−π0+ are reduced by factors of 3.9 and 2.6, respectively. The reported results provide important inputs for the precise measurement of the angle γ of the Cabibbo-Kobayashi-Maskawa matrix and indirect CP violation in charm mixing.
By analyzing e+e− annihilation data corresponding to an integrated luminosity of 7.93 fb−1, collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we search for the semileptonic decays D0→K−ηe+νe, D+→K0Sηe+νe and D+→ηηe+νe for the first time. We present evidence for D0→K−ηe+νe with a significance of 3.3σ. The branching fraction of D0→K−ηe+νe is measured to be (0.84+0.29−0.34±0.22)×10−4. %Alternatively, under the assumption that this decay is dominated by non-resonant, the branching fraction is determined to be (1.12+0.45−0.38±0.05)×10−4. Here, the first uncertainties are statistical and the second ones are systematic. No significant signals are observed for the decays D+→K0Sηe+νe and D+→ηηe+νe and we set the upper limits on their branching fractions.
By analyzing e+e− annihilation data corresponding to an integrated luminosity of 7.93 fb−1, collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we search for the semileptonic decays D0→K−ηe+νe, D+→K0Sηe+νe and D+→ηηe+νe for the first time. We present evidence for D0→K−ηe+νe with a significance of 3.3σ. The branching fraction of D0→K−ηe+νe is measured to be (0.84+0.29−0.34±0.22)×10−4. Here, the first uncertainties are statistical and the second ones are systematic. No significant signals are observed for the decays D+→K0Sηe+νe and D+→ηηe+νe and we set the upper limits on their branching fractions.
In the effective field theory, the massless dark photon γ′ can only couple with the Standard Model particle through operators of dimension higher than four, thereby offering a high sensitivity to the new physics energy scale. Using 7.9 fb−1 of e+e− collision data collected at s√=3.773 GeV with the BESIII detector at the BEPCII collider, we measure the effective flavor-changing neutral current coupling of cuγ′ in D0→ωγ′ and D0→γγ′ processes to search for the massless dark photon. No significant signals are observed, and the upper limits at the 90% confidence level on the massless dark photon branching fraction are set to be 1.1×10−5 and 2.0×10−6 for D0→ωγ′ and D0→γγ′, respectively. These results provide the most stringent constraint on the new physics energy scale associated with cuγ′ coupling in the world, with the new physics energy scale related parameter |C|2+|C5|2<8.2×10−17 GeV−2 at the 90% confidence level, playing a unique role in the dark sector search with the charm sector.
Based on a sample of (448.1±2.9)×106 ψ(3686) events collected with the BESIII detector at BEPCII, the decays of ψ(3686)→K−ΛΞ¯¯¯¯++c.c. with Ξ¯¯¯¯+→Λ¯¯¯¯π+, Λ¯¯¯¯→p¯¯¯π+ are this http URL excited hyperons, Ξ(1690)− and Ξ(1820)−, are observed with large significance (≫10σ) in the K−Λ invariant mass distributions. A partial wave analysis is performed, and the spin-parities of Ξ(1690)− and Ξ(1820)− are determined to be 12− and 32−, respectively. The masses, widths, and product branching fractions of Ξ(1690)− and Ξ(1820)− are also measured.
Based on a sample of (448.1±2.9)×106 ψ(3686) events collected with the BESIII detector at BEPCII, the decays of ψ(3686)→K−ΛΞ¯¯¯¯++c.c. with Ξ¯¯¯¯+→Λ¯¯¯¯π+, Λ¯¯¯¯→p¯¯¯π+ are this http URL excited hyperons, Ξ(1690)− and Ξ(1820)−, are observed with large significance (≫10σ) in the K−Λ invariant mass distributions. A partial wave analysis is performed, and the spin-parities of Ξ(1690)− and Ξ(1820)− are determined to be 12− and 32−, respectively. The masses, widths, and product branching fractions of Ξ(1690)− and Ξ(1820)− are also measured.