Using e+e− collision data corresponding to an integrated luminosity of 7.33 fb−1 recorded by the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, we present an analysis of the decay Ds+→π+π−e+νe, where the Ds+ is produced via the process e+e−→Ds*±Ds∓. We observe the f0(980) in the π+π− system and the branching fraction of the decay Ds+→f0(980)e+νe with f0(980)→π+π− measured to be (1.72±0.13stat±0.10syst)×10−3, where the uncertainties are statistical and systematic, respectively. The dynamics of the Ds+→f0(980)e+νe decay are studied with the simple pole parametrization of the hadronic form factor and the Flatté formula describing the f0(980) in the differential decay rate, and the product of the form factor f+f0(0) and the c→s Cabibbo-Kobayashi-Maskawa matrix element |Vcs| is determined for the first time to be f+f0(0)|Vcs|=0.504±0.017stat±0.035syst. Furthermore, the decay Ds+→f0(500)e+νe is searched for the first time but no signal is found. The upper limit on the branching fraction of Ds+→f0(500)e+νe, f0(500)→π+π− decay is set to be 3.3×10−4 at 90% confidence level.Received 23 March 2023Revised 29 November 2023Accepted 28 February 2024DOI:https://doi.org/10.1103/PhysRevLett.132.141901Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLeptonic, semileptonic & radiative decaysMultiquark bound statesQuantum chromodynamicsStrong interactionPhysical SystemsCharm quarkMesonsPropertiesForm factorsParticles & Fields

Using (27.12 +/- 0.14) x 10(8) psi(3686) decays and data samples of e(+)e(-) collisions with root s from 4.130 to 4.780 GeV collected with the BESIII detector, we report the first observation of the electromagnetic Dalitz transition h(c) -> e(+)e(-)eta(c) with a statistical significance of 5.4 sigma. We measure the ratio of the branching fractions B(h(c) -> e(+)e(-)eta(c))/B(h(c) -> gamma eta(c)) separately for the h(c) samples produced via psi(3686) -> pi(0)h(c) and e(+)e(-) -> pi(+)pi(-)h(c). The average ratio is determined to be (0.59 +/- 0.10(stat) +/- 0.04(syst))%, where the uncertainty includes both statistical and systematic components.

Using a data sample of 4.481 x 108 psi o3686 thorn events collected with the BESIII detector, we report the first observation of the four-lepton-decays J=psi -> e thorn e-e thorn e- and J=psi -> e thorn e-mu thorn mu- utilizing the process psi o3686 thorn -> pi thorn pi-J=psi. The branching fractions are determined to be 1/25.48 0.31ostat thorn 0.45osyst thorn x 10-5 and 1/23.53 0.22ostat thorn 0.13osyst thorn x 10-5, respectively. The results are consistent with theoretical predictions. No significant signal is observed for J=psi -> mu thorn mu-mu thorn mu-, and an upper limit on the branching fraction is set at 1.6 x 10-6 at the 90% confidence level. A CP asymmetry observable is constructed for the first two channels, which is measured to be o-0.012 0.054 0.010 thorn and o0.062 0.059 0.006 thorn , respectively. No evidence for CP violation is observed in this process

Using (27.12± 0.14)×10^8 ψ(3686) decays and data samples of e^+e^- collisions with √(s) from 4.130 to 4.780 GeV collected with the BESIII detector, we report the first observation of the electromagnetic Dalitz transition h_c→ e^+e^-η_c with a statistical significance of 5.4σ. We measure the ratio of the branching fractions ℬ(h_c→ e^+e^-η_c)/ℬ(h_c→ γη_c) separately for the h_c samples produced via ψ(3686)^0h_c and e^+e^-^+π^-h_c. The average ratio is determined to be (0.59±0.10(stat.)±0.04(syst.))%, where the uncertainty includes both statistical and systematic components.

Using e+e− collision data, corresponding to an integrated luminosity of 892 pb−1 collected at center-of-mass energies from 4.84 to 4.95 GeV with the BESIII detector, we search for the process e+e−→K+K−ψ(3770) by reconstructing two charged kaons and one D meson from ψ(3770). No significant signal of e+e−→K+K−ψ(3770) is found and the upper limits of the Born cross sections are reported at 90% confidence level. Published by the American Physical Society 2024

The absolute branching fraction of the decay Λc(2625)+→Λc+π+π− is measured for the first time to be (50.2±5.7stat±3.5syst)% with 368.48 pb−1 of e+e− collision data collected by the BESIII detector at the center-of-mass energies of s=4.918 and 4.950 GeV. Although the central value of the result is lower than the theoretical prediction of 67%, obtained from isospin symmetry, they are consistent taking the uncertainties into account. This is the first absolute branching fraction measurement for Λc(2625)+ since it was found. This measurement is necessary to obtain the coupling constants for the transitions between s-wave and p-wave charmed baryons in heavy hadron chiral perturbation theory. In addition, we search for the decay Λc(2595)+→Λc+π+π−. No significant signal is observed, and the upper limit on its branching fraction is determined to be 85.0% at the 90% confidence level. Published by the American Physical Society 2024

We report the measurement of the cross sections for $e^+e^-\rightarrow {\rm hadrons}$ at center-of-mass (c.m.) energies from 3.645 to 3.871 GeV. We observe a new resonance $\mathcal R(3810)$ in the cross sections for the first time, and observe the $\mathcal R(3760)$ resonance with high significance in the cross sections. The $\mathcal R(3810)$ has a mass of $(3804.5 \pm 0.9 \pm 0.9)$ ~MeV/$c^2$, a total width of $(5.4 \pm 3.5 \pm 3.2)$~MeV, and an electronic partial width of $(19.4 \pm 7.4 \pm 12.1)$~eV. Its significance is $7.7\sigma$. The $\mathcal R(3810)$ could be interpreted as a hadro-charmonium resonance predicted by Quantum Chromodynamics (QCD). In addition, we measure the mass $(3751.9\pm 3.8\pm 2.8)$ ~MeV/$c^2$, the total width $(32.8 \pm 5.8 \pm 8.7)$~MeV, and the electronic partial width $(184\pm 75\pm 86)$~eV with improved precision for the $\mathcal R(3760)$. Furthermore, for the $\mathcal R(3780)$ we measure the mass $(3778.7\pm 0.5\pm 0.3)$ ~MeV/$c^2$ and total width $(20.3 \pm 0.8 \pm 1.7)$~MeV with improved precision, and the electronic partial width $(265\pm 69\pm 83)$~eV. The $\mathcal R(3780)$ can be interpreted as the $1^3D_1$ state of charmonium. Its mass and total width differ significantly from the corresponding fitted values given by the Particle Data Group in 2022 by 7.1 and 3.2 times the uncertainties for $\psi(3770)$, respectively. $\psi(3770)$ has been interpreted as the $1^3D_1$ state for 45 years.

We present measurements of the Born cross sections for the processes e^{+}e^{-}→ωχ_{c1} and ωχ_{c2} at center-of-mass energies sqrt[s] from 4.308 to 4.951 GeV. The measurements are performed with data samples corresponding to an integrated luminosity of 11.0 fb^{-1} collected with the BESIII detector operating at the Beijing Electron Positron Collider storage ring. Assuming the e^{+}e^{-}→ωχ_{c2} signals come from a single resonance, the mass and width are determined to be M=(4413.6±9.0±0.8) MeV/c^{2} and Γ=(110.5±15.0±2.9) MeV, respectively, which is consistent with the parameters of the well-established resonance ψ(4415). In addition, we also use one single resonance to describe the e^{+}e^{-}→ωχ_{c1} line shape and determine the mass and width to be M=(4544.2±18.7±1.7) MeV/c^{2} and Γ=(116.1±33.5±1.7) MeV, respectively. The structure of this line shape, observed for the first time, requires further understanding.

We present cross sections for the reaction e+e−→KS0KL0 at center-of-mass energies ranging from 3.51 to 4.95 GeV using data samples collected in the BESIII experiment, corresponding to a total integrated luminosity of 26.5 fb−1. The ratio of neutral-to-charged kaon form factors at large momentum transfers (12

Using data samples with an integrated luminosity of 4.5 fb−1 collected by the BESIII detector at center-of-mass energies ranging from 4.66 GeV to 4.95 GeV, we study the processes of e+e−→ωX(3872) and e+e−→γX(3872). With the e+e−→ωX(3872) process, the branching fraction ratio R≡B(X(3872)→γJ/ψ)B(X(3872)→π+π−J/ψ) is measured to be 0.38±0.20stat±0.01syst (R<0.83 at 90% confidence level). In addition, we measure the ratio of the average cross section of e+e−→ωX(3872) to e+e−→ωχc1(ωχc2) to be σωX(3872)/σωχc1(σωX(3872)/σωχc2)=5.2±1.0stat±1.9syst(5.5±1.1stat±2.4syst). Finally, we search for the process of e+e−→γX(3872), and no obvious signal is observed. The upper limit on the ratio of the average cross section of e+e−→γX(3872) to e+e−→ωX(3872) is set as σγX(3872)/σωX(3872)<0.23 at 90% confidence level. Published by the American Physical Society 2024

Six C-even states, denoted as X, with quantum numbers JPC=0−+, 1±+, or 2±+, are searched for via the e+e−→γDs±Ds*∓ process using (1667.39±8.84) pb−1 of e+e− collision data collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energy of s=(4681.92±0.30) MeV. No statistically significant signal is observed in the mass range from 4.08 GeV/c2 to 4.32 GeV/c2. The upper limits of σ[e+e−→γX]·B[X→Ds±Ds*∓] at a 90% confidence level are determined. Published by the American Physical Society 2024

Cross sections for the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}^{0}{K}_{S}^{0}J/\ensuremath{\psi}$ at center-of-mass energies from 4.128 to 4.950 GeV are measured using data samples with a total integrated luminosity of $21.2\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the BESIII detector operating at the BEPCII storage ring. The $Y(4230)$ state is observed in the energy dependence of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}^{0}{K}_{S}^{0}J/\ensuremath{\psi}$ cross section for the first time with a statistical significance of $26.0\ensuremath{\sigma}$. In addition, an enhancement around 4.710 GeV, labeled as the $Y(4710)$, is seen with a statistical significance of $4.2\ensuremath{\sigma}$. There is no clear structure around 4.484 GeV. Using a fit with a coherent sum of three Breit-Wigner functions, we determine the mass and width of the $Y(4230)$ state to be $4226.9\ifmmode\pm\else\textpm\fi{}6.6\ifmmode\pm\else\textpm\fi{}22.0\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $71.7\ifmmode\pm\else\textpm\fi{}16.2\ifmmode\pm\else\textpm\fi{}32.8\text{ }\text{ }\mathrm{MeV}$, respectively, and the mass and width of the $Y(4710)$ state to be $4704.0\ifmmode\pm\else\textpm\fi{}52.3\ifmmode\pm\else\textpm\fi{}69.5\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $183.2\ifmmode\pm\else\textpm\fi{}114.0\ifmmode\pm\else\textpm\fi{}96.1\text{ }\text{ }\mathrm{MeV}$, respectively, where the first uncertainties are statistical and the second are systematic. In addition, the average Born cross section ratio $\frac{{\ensuremath{\sigma}}^{\text{Born}}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}^{0}{K}_{S}^{0}J/\ensuremath{\psi})}{{\ensuremath{\sigma}}^{\text{Born}}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}J/\ensuremath{\psi})}$ is measured to be ${0.388}_{\ensuremath{-}0.028}^{+0.035}\ifmmode\pm\else\textpm\fi{}0.016$, or ${0.426}_{\ensuremath{-}0.031}^{+0.038}\ifmmode\pm\else\textpm\fi{}0.018$ if three-body phase space is considered.

We present a measurement of the dressed cross sections for e+e- -> phi eta at different center-of-mass energies between 3.508 and 4.600 GeV based on 15.1 fb-1 of e+e- annihilation data collected with the BESIII detector operating at the BEPCII collider. In addition, a search for the decay Y(4230) -> phi eta is performed. No clear signal is observed and the corresponding upper limit is provided.

The study of the Cabibbo-favored semileptonic decay ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ is reported using $4.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of ${e}^{+}{e}^{\ensuremath{-}}$ annihilation data collected at center-of-mass energies ranging from 4.600 to 4.699 GeV. The branching fraction of the decay is measured to be $\mathcal{B}({\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}})=(3.48\ifmmode\pm\else\textpm\fi{}0.1{4}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.1{0}_{\mathrm{syst}})%$, 3 times more precise than the prior world average result. Tests of lepton flavor universality using ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\ell}}^{+}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ ($\ensuremath{\ell}=e$, $\ensuremath{\mu}$) decays are reported for the first time, based on measurements of the differential decay rates and the forward-backward asymmetries in separate four-momentum transfer regions. The results are compatible with Standard Model predictions. Furthermore, we improve the determination of the form-factor parameters in ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\ell}}^{+}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ decays, which provide stringent tests and calibration for lattice quantum chromodynamics calculations.

Using (1.0087±0.0044)×10^{10} J/ψ events collected with the BESIII detector at the BEPCII storage ring, the process Ξ^{0}n→Ξ^{-}p is studied, where the Ξ^{0} baryon is produced in the process J/ψ→Ξ^{0}Ξ[over ¯]^{0} and the neutron is a component of the ^{9}Be, ^{12}C, and ^{197}Au nuclei in the beam pipe. A clear signal is observed with a statistical significance of 7.1σ. The cross section of the reaction Ξ^{0}+^{9}Be→Ξ^{-}+p+^{8}Be is determined to be σ(Ξ^{0}+^{9}Be→Ξ^{-}+p+^{8}Be)=(22.1±5.3_{stat}±4.5_{sys}) mb at the Ξ^{0} momentum of 0.818 GeV/c, where the first uncertainty is statistical and the second is systematic. No significant H-dibaryon signal is observed in the Ξ^{-}p final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.

A search for the hadronic decays of the h(c) meson to the final states p (p) over bar pi(+)pi(-)pi(0) , pp eta , and pp pi 0 via the process psi (3686) -> pi(0)h(c) is performed using (4.48 +/- 0.03) x 10(8) psi (3686) events collected with the BESIII detector. The decay channel h(c) -> p (p) over bar eta is observed for the first time with a significance greater than 5 sigma and a branching fraction of (6.41 +/- 1.74 +/- 0.53 +/- 1.00) x 10(-4) , where the uncertainties are statistical, systematic, and that from the branching fraction of psi (3686) -> pi(0)h(c). Strong evidence for the decay h(c) -> p (p) over bar pi(+)pi(-)pi(0) is found with a significance of 4.9 sigma and a branching fraction of (3.84 +/- 0.83 +/- 0.69 +/- 0.58) x 10(-3). The significances include systematic uncertainties. No clear signal of the decay h(c) -> p (p) over bar pi(0) is found, and an upper limit of 6.59 x 10(-4) on its branching fraction is set at the 90% confidence level.

We report on the first search for Λ[over ¯]-Λ oscillations in the decay J/ψ→pK^{-}Λ[over ¯]+c.c. by analyzing 1.31×10^{9} 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 sqrt[s]=3.097 GeV. No evidence for hyperon oscillations is observed. The upper limit for the oscillation rate of Λ[over ¯] to Λ hyperons is determined to be P(Λ)=[B(J/ψ→pK^{-}Λ+c.c.)/B(J/ψ→pK^{-}Λ[over ¯]+c.c.)]<4.4×10^{-6} corresponding to an oscillation parameter δm_{ΛΛ[over ¯]} of less than 3.8×10^{-18} GeV at the 90% confidence level.

Using data samples of e+e− collisions collected with the BESIII detector at eight center-of-mass energy points between 3.49 and 3.67 GeV, corresponding to an integrated luminosity of 670 pb−1, we present the upper limits of Born cross sections and the effective form factor for the process e+e−→Ω−¯Ω+. A fit to the cross sections using a perturbative QCD-derived energy-dependent function shows no significant threshold effect. The upper limit on the measured effective form factor is consistent with a theoretical prediction within the uncertainty of 1σ. These results provide new experimental information on the production mechanism of Ω.Received 7 December 2022Accepted 5 January 2023DOI:https://doi.org/10.1103/PhysRevD.107.052003Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Particle interactionsResearch AreasParticle phenomenaParticle interactionsResearch AreasForm factorsParticle interactionsTotal cross sectionsParticles & Fields