Based on 6.1  fb^{-1} of e^{+}e^{-} annihilation data collected at center-of-mass energies from 4.600 to 4.843 GeV with the BESIII detector at the BEPCII collider, a partial wave analysis of Λ_{c}^{+}→Λπ^{+}η is performed, and branching fractions and decay asymmetry parameters of intermediate processes are determined. The process Λ_{c}^{+}→Λa_{0}(980)^{+} is observed for the first time, and evidence for the pentaquark candidate Σ(1380)^{+} decaying into Λπ^{+} is found with statistical significance larger than 3σ with mass and width fixed to theoretical predictions. The branching fraction product B[Λ_{c}^{+}→Λa_{0}(980)^{+}]B[a_{0}(980)^{+}→π^{+}η] is determined to be (1.05±0.16_{stat}±0.05_{syst}±0.07_{ext})%, which is larger than theoretical calculations by 1-2 orders of magnitude. Here the third (external) systematic is from B(Λ_{c}^{+}→Λπ^{+}η). Finally, we precisely obtain the absolute branching fraction B(Λ_{c}^{+}→Λπ^{+}η)=(1.94±0.07_{stat}±0.11_{syst})%.

The process e^+e^-→K_S^0K_S^0ψ (3686) is studied by analyzing e+e− collision data samples collected at eight center-of-mass energies ranging from 4.682 to 4.951 GeV with the BESIII detector operating at the BEPCII collider, corresponding to an integrated luminosity of 4.1 fb−1. Observation of the e^+e^-→K_S^0K_S^0ψ (3686) process is found for the first time with a statistical significance of 6.3σ, and the cross sections at each center-of-mass energy are measured. The ratio of cross sections of e^+e^-→K_S^0K_S^0ψ (3686) relative to e+e− → K+K−ψ(3686) is determined to be σ(e^+e^-→K_S^0K_S^0ψ (3686))/σ(e^+e^-→K^+K^-ψ (3686))=0.45± 0.25 , which is consistent with the prediction based on isospin symmetry. The uncertainty includes both statistical and systematic contributions. Additionally, the K_S^0ψ (3686) invariant mass distribution is found to be consistent with three-body phase space. The significance of a contribution beyond three-body phase space is only 0.8σ.

Using 7.9fb−1 of e+e− collision data collected at s=3.773 GeV with the BESIII detector at the BEPCII collider, we search for the massless dark photon with the flavor-changing neutral current processes D0→ωγ′ and D0→γγ′ for the first time. 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. Published by the American Physical Society 2025

Based on a sample of (2712.4 ± 14.3) × 106 ψ(3686) events collected with the BESIII detector, a partial wave analysis of the decay ψ (3686)→ΛΣ^0π^0 + c.c. is performed to investigate Λ* and Σ* resonances in the π^0Σ^0 and π0Λ invariant mass distributions. Significant contributions are found from the Λ(1405), Λ(1520), Λ(1600), Λ(1670), Λ(1690), Λ(1800), Λ(1890), Λ(2325), Σ(1385), Σ(1660), Σ(1670), Σ(1750), and Σ(1910). The masses, widths, and production branching fractions for each component are determined. In addition, the branching fraction of ψ (3686)→ΛΣ^0π^0 + c.c. is measured to be (1.544 ± 0.013 ± 0.071) × 10−4 for the first time, where the first uncertainty is statistical and the second systematic.

A bstract Based on 7.33 fb − 1 of e + e − collision data collected by the BESIII detector operating at the BEPCII collider at center-of-mass energies from 4.128 to 4.226 GeV, a search for the Majorana neutrino ν m is conducted in the lepton-number-violating decays of $$ {D}_{\textrm{s}}^{+} $$ D s + → h − h 0 e + e + . Here, h − represents a K − or π − , and h 0 represents a π 0 , $$ {K}_S^0 $$ K S 0 or ϕ . No significant signal is observed, and the upper limits of their branching fractions at the 90% confidence level are determined to be $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕπ − e + e + ) < 6 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕK − e + e + ) < 9 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → $$ {K}_S^0 $$ K S 0 π − e + e + ) < 1 . 3 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → $$ {K}_S^0 $$ K S 0 K − e + e + ) < 2 . 9 × 10 − 5 , $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → π − π 0 e + e + ) < 2 . 9 × 10 − 5 and $$ \mathcal{B} $$ B ( $$ {D}_{\textrm{s}}^{+} $$ D s + → K − π 0 e + e + ) < 3 . 4 × 10 − 5 . The Majorana neutrino is searched for with different mass assumptions within the range [0 . 20 , 0 . 80] GeV /c 2 in the decay of $$ {D}_{\textrm{s}}^{+} $$ D s + → ϕe + ν m with ν m → π − e + , and the upper limits of the branching fractions at the 90% confidence level are at the level of 10 − 5 –10 − 2 , depending on the mass of the Majorana neutrino.

Abstract Based on a data sample of (10087 ± 44) × 106 J/ψ events taken with the BESIII detector, we search for the flavor-changing neutral current charmonium decay J/ψ → D 0 μ + μ − + c.c. . No significant signal above the background is observed, and the upper limit on its branching fraction is set to be ℬ(J/ψ → D 0 μ + μ − + c.c.) < 1.1 × 10 −7 at the 90% confidence level. This marks the first search for a flavor-changing neutral current charmonium decay involving muons in the final state.

A bstract By analyzing e + e − collision data with an integrated luminosity of 7.9 fb − 1 collected with the BESIII detector at the center-of-mass energy of 3.773 GeV, the branching fraction of D + → τ + ν τ is determined as $$ \mathcal{B} $$ B = (9.9 ± 1.1 stat ± 0.5 syst ) × 10 − 4 . Using the most precise result $$ \mathcal{B} $$ B ( D + → μ + ν μ ) = (3.981 ± 0.079 stat ± 0.040 syst ) × 10 − 4 [1], we determine R τ/μ = Γ( D + → τ + ν τ )/Γ( D + → μ + ν μ ) = 2.49 ± 0.31, achieving a factor of two improvement in precision compared to the previous BESIII result. This measurement is in agreement with the standard model prediction of lepton flavor universality within one standard deviation.

We measure the Born cross section for the reaction e+e−→ηhc from s=4.129 to 4.600 GeV using datasets collected by the BESIII detector running at the BEPCII collider. A resonant structure in the cross-section line shape near 4.200 GeV is observed with a statistical significance of 7σ. The parameters of this resonance are measured to be M=4188.8±4.7±8.0 MeV/c2 and Γ=49±16±19 MeV, where the first uncertainties are statistical and the second systematic. Published by the American Physical Society 2025

Based on (2712.4 ± 14.3) × 106 ψ(3686) events collected at the BESIII detector operating at the BEPCII collider, we present the first observation of the decay ψ (3686)→K^-Λ (1520)Ξ^+ + c.c.. The product branching fraction ℬ[ψ (3686)→K^-Λ (1520)Ξ^++c.c.]×ℬ[Λ (1520)→ pK^-] is measured to be (9.47 ± 0.75 ± 0.97) × 10−7, where the first uncertainty is statistical and the second systematic.

The Spin Physics Detector collaboration proposes to install a universal detector in the second interaction point of the NICA collider under construction (JINR, Dubna) to study the spin structure of the proton and deuteron and other spin-related phenomena using a unique possibility to operate with polarized proton and deuteron beams at a collision energy up to 27 GeV and a luminosity up to 10^32 cm^-2 s^-1. As the main goal, the experiment aims to provide access to the gluon TMD PDFs in the proton and deuteron, as well as the gluon transversity distribution and tensor PDFs in the deuteron, via the measurement of specific single and double spin asymmetries using different complementary probes such as charmonia, open charm, and prompt photon production processes. Other polarized and unpolarized physics is possible, especially at the first stage of NICA operation with reduced luminosity and collision energy of the proton and ion beams. This document is dedicated exclusively to technical issues of the SPD setup construction.

We perform the first amplitude analysis of D_{s}^{+}→π^{+}π^{+}π^{-}π^{0} decays based on data samples of electron-positron collisions recorded with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of 7.33  fb^{-1}. We report the observation of D_{s}^{+}→f_{0}(980)ρ(770)^{+} with a statistical significance greater than 10σ and determine the branching fractions B(D_{s}^{+}→π^{+}π^{+}π^{-}π^{0}|_{non-η})=(2.04±0.08_{stat}±0.05_{syst})% and B(D_{s}^{+}→ηπ^{+})=(1.56±0.09_{stat}±0.04_{syst})%. Moreover, we measure the relative branching fraction between ϕ→π^{+}π^{-}π^{0} and ϕ→K^{+}K^{-} to be [B(ϕ(1020)→π^{+}π^{-}π^{0})/B(ϕ(1020)→K^{+}K^{-})]=0.230±0.014_{stat}±0.010_{syst}., which deviates from the world average value by more than 4σ.

Abstract The process e + e − → K S 0 K S 0 ψ 3686 $$ {e}^{+}{e}^{-}\to {K}_S^0{K}_S^0\psi (3686) $$ is studied by analyzing e + e − collision data samples collected at eight center-of-mass energies ranging from 4.682 to 4.951 GeV with the BESIII detector operating at the BEPCII collider, corresponding to an integrated luminosity of 4.1 fb −1. Observation of the e + e − → K S 0 K S 0 ψ 3686 $$ {e}^{+}{e}^{-}\to {K}_S^0{K}_S^0\psi (3686) $$ process is found for the first time with a statistical significance of 6.3σ, and the cross sections at each center-of-mass energy are measured. The ratio of cross sections of e + e − → K S 0 K S 0 ψ 3686 $$ {e}^{+}{e}^{-}\to {K}_S^0{K}_S^0\psi (3686) $$ relative to e + e − → K + K − ψ(3686) is determined to be σ e + e − → K S 0 K S 0 ψ 3686 σ e + e − → K + K − ψ 3686 = 0.45 ± 0.25 $$ \frac{\sigma \left({e}^{+}{e}^{-}\to {K}_S^0{K}_S^0\psi (3686)\right)}{\sigma \left({e}^{+}{e}^{-}\to {K}^{+}{K}^{-}\psi (3686)\right)}=0.45\pm 0.25 $$ , which is consistent with the prediction based on isospin symmetry. The uncertainty includes both statistical and systematic contributions. Additionally, the K S 0 ψ 3686 $$ {K}_S^0\psi (3686) $$ invariant mass distribution is found to be consistent with three-body phase space. The significance of a contribution beyond three-body phase space is only 0.8σ.

Utilizing a dataset of 6.7 fb(-1) from electron-positron collisions recorded by the BESIII detector at the BEPCII storage ring, a search is conducted for the processes e(+)e(-) -> phi chi(c0) and phi eta(c2)(1D) across centerof-mass energies from 4.47 to 4.95 GeV. In the absence of any significant signals, upper limits are set. These include limits on the dressed cross sections for e(+)e(-) -> phi chi(c0), as well as the product of the dressed cross section for e(+)e(-) -> phi eta(c2)(1D) and a sum of five branching fractions. Furthermore, the product of the electronic width of Y(4660) and the branching fraction of the Y(4660) ->phi chi(c0), denoted as Gamma Y-e+e-((4660)) B-Y(4660)->phi chi(c0), is determined to be <0.35 eV at the 90% confidence level.

We report an improved study of the semileptonic decay D^0→K^0π^-e^+ν_e based on a sample of 7.9 fb−1 of e+e− annihilation data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider. The branching fraction of this decay is measured to be ℬ(D^0→K^0π^-e^+ν_e) = (1.444 ± 0.022stat ± 0.024syst) ℬ(D^0→K^∗(892)^-e^+ν_e) = (2.039 ± 0.032stat ± 0.034syst) K^0π^- 𝒮 -wave component is found to account for (5.87 ± 0.32stat ± 0.16syst) B[D^0→(K^0π^-)_S-wavee^+ν_e] = (0.085 ± 0.005stat ± 0.003syst)

Using $e^+ e^-$ collision data collected at the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of $7.33~{\rm fb}^{-1}$, we determine the absolute branching fractions of fifteen hadronic $D_s^{+}$ decays with a double-tag technique. In particular, we make precise measurements of the branching fractions $\mathcal{B}(D_s^+ \to K^+ K^- \pi^+)=(5.49 \pm 0.04 \pm 0.07)\%$, $\mathcal{B}(D_s^+ \to K_S^0 K^+)=(1.50 \pm 0.01 \pm 0.01)\%$ and $\mathcal{B}(D_s^+ \to K^+ K^- \pi^+ \pi^0)=(5.50 \pm 0.05 \pm 0.11)\%$, where the first uncertainties are statistical and the second ones are systematic. The \emph{CP} asymmetries in these decays are also measured and all are found to be compatible with zero.

Using e+e− collision data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 3.510 and 4.914 GeV, corresponding to an integrated luminosity of 25 fb−1, we measure the Born cross sections for the process e^+e^-→K^-Ξ^+Λ /Σ^0 at thirty-five energy points with a partial-reconstruction strategy. By fitting the dressed cross sections of e^+e^-→K^-Ξ^+Λ /Σ^0 , evidence for ψ (4160)→K^-Ξ^+Λ is found for the first time with a significance of 4.4σ, including systematic uncertainties. No evidence for other possible resonances is found. In addition, the products of electronic partial width and branching fraction for all assumed resonances decaying into K^-Ξ^+Λ /Σ^0 are determined.

Based on (2.712 +/- 0.014) x 10(9) psi(3686) events collected by the BESIII Collaboration, evidence of the hadronic decay h(c) -> (KSK+)-K-0 pi(-) + c.c. is found with a significance of 4.3 sigma in the psi(3686) -> pi(0)h(c) process. The branching fraction of h(c) -> (KSK+)-K-0 pi(-) + c.c. is measured to be (7.3 +/- 1.8 +/- 0.8) x 10(-4), where the first and second uncertainties are statistical and systematic, respectively. Combining with the exclusive decay width of eta(c) -> K (K) over bar pi, our result indicates inconsistencies with both pQCD and NRQCD predictions.

Based on (10.09 +/- 0.04) x 10(9) J/psi events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay J/psi -> phi pi(0 eta). is performed. We observe for the first time two new structures on the phi eta invariant mass distribution, with significances exceeding 27 sigma and 13 sigma; the first with J(PC) = 1(+-), mass M = (1908 +/- 6(stat)(-4)(+8) (sys)) MeV/c(2), and width Gamma = (175 +/- 13(stat)(-16)(+7) (sys)) MeV, the second with J(PC) = 1(--), mass M = (1992 +/- 12 (stat)(-6)(+15) (sys)) MeV/c(2), and width Gamma = (132 +/- 22(stat)(-4)(+17) (sys)) MeV. These measurements provide important input for the strangeonium spectrum. In addition, the f(0) (980) - a(0)(980)(0) mixing signal in J/psi -> phi f(0)(980) -> phi a(0)(980)(0) and the corresponding electromagnetic decay J/psi -> phi a(0)(980)(0) are measured with improved precision, providing crucial information to understand the nature of a(0)(980)(0) and f(0)(980).

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.

Based on (2712.4±14.3)×106 e+e−→ψ(3686) events collected with the BESIII detector operating at the BEPCII Collider, we report the first evidence of χc0→ΛΛ¯ϕ decays and the first observation of χc1,2→ΛΛ¯ϕ decays, with significances of 4.1σ, 11.3σ and 13.0σ, respectively. The decay branching fractions of χc0,1,2→ΛΛ¯ϕ are measured to be (2.99±1.24±0.19)×10−5, (6.01±0.90±0.40)×10−5, and (7.13±0.81±0.36)×10−5, where the first uncertainties are statistical and the second systematic. No obvious enhancement near the ΛΛ¯ production threshold or excited Λ state is found in the Λϕ (or Λ¯ϕ) system. Published by the American Physical Society 2024