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BESIII Collaboration

Publications and source records attributed to BESIII Collaboration.

At least 55 records · Page 3Linked to original sources

arXiv2026

Lightest $0^{-+}$ Glueball as Dominant Constituent of $X(2370)$

With 10 billion $J/ψ$ events collected at \mbox{BESIII}, the decay of $X(2370)\rightarrow K^{*}(892)^{0}\bar{K}^{0}+\mathrm{c.c.}$ is searched for via the $J/ψ\rightarrowγK_{S}^{0}K_{S}^{0}π^{0}$ process. No evidence of this decay mode is found, with $\mathcal{B}[J/ψ\rightarrowγX(2370)] \times \mathcal{B}[ X(2370) \rightarrow K^{*}(892)^{0}\bar{K}^{0}+\mathrm{c.c.} \rightarrow K^{0}_{S}K^{0}_{S}π^{0}] < 2.7\times 10^{-6}$ at the $90\%$ confidence level. The suppression of the $K^{*}(892)\bar{K}$ mode indicates the $X(2370)$ as a flavor-singlet state. It is the first flavor-singlet light hadron observed above $1~\textrm{GeV}/c^{2}$. All \mbox{BESIII} measurements on the $X(2370)$ are summarized. A dominant component of the lightest $0^{-+}$ glueball is essential for a natural and complete explanation of the properties of the $X(2370)$~\textemdash~the mass, spin-parity, high production rate in $J/ψ$ radiative decays, decay pattern similarities to that of $η_{c}$, flavor-singlet property, narrow partial decay width, and suppression of radiative decays to $ω$ and $ϕ$, since these properties are all consistent with the features of the lightest $0^{-+}$ glueball while other interpretations at present are disfavored. This supports that the lightest $0^{-+}$ glueball is the dominant constituent of the $X(2370)$.

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arXiv2026

Measurement of the double Dalitz decay $η\to e^+e^-e^+e^-$

Using a data sample of $(1.0087 \pm 0.0044) \times {10^{10}}$ $J/ψ$ events collected with the BESIII detector, we study the rare double Dalitz decay of $η\rightarrow e^+e^-e^+e^-$ through the processes $J/ψ\rightarrow γη$ and $J/ψ\rightarrow γη' ,η' \to π^+π^-η$. Clear $η$ signals are observed in the $e^+e^-e^+e^-$ invariant mass spectrum, with statistical significances of 5.9$σ$ and 7.8$σ$ for the two channels, respectively. By combining both modes, we determine the branching fraction of $η\rightarrow e^+ e^- e^+ e^-$ to be $(2.63~\pm~0.34_{\rm stat}~\pm~0.16_{\rm syst}) \times10^{-5}$. The result is consistent with the previous measurements within uncertainties and further constrains physics beyond the standard model.

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arXiv2026

Observation of $η_{c} \to p\bar{p}η$ via $ψ(3686) \to γp\bar{p}η$

The decay $η_c\to p\bar{p}η$ is observed for the first time with a significance of exceeding $10σ$. It is found by analyzing $(2712.4 \pm 14.3)\times10^{6}$ $ψ(3686)$ events accumulated at the BESIII detector. The measured branching fraction of $η_c\to p\bar{p}η$ via $ψ(3686) \to γp \bar{p} η$ is significantly influenced by the interference between the resonant $η_c$ decay and the non-resonant process $ψ(3686) \to γp \bar{p} η$ and is measured in both constructive- and destructive-interference scenarios. The joint branching fraction of $ψ(3686)\to γη_c$, $η_c\to p\bar{p}η$ is measured to be $(3.2 \pm 0.1 \pm 0.9)\times10^{-6}$ or $(8.7 \pm 0.3 \pm 2.1)\times10^{-6}$ for constructive- or destructive-interference solutions, respectively, where the first uncertainties are statistical and the second systematic. The branching fraction of $η_c\to p\bar{p}η$ is determined to be $\mathcal{B}(η_c\to p\bar{p}η)=(0.90 \pm 0.04 \pm 0.21 \pm 0.13)\times10^{-3}$ or $(2.42 \pm 0.07 \pm 0.48 \pm 0.34)\times10^{-3}$ for the two solutions, respectively, where the third uncertainties are due to the uncertainty in the branching fraction of $ψ(3686)\to γη_c$.

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arXiv2026

Amplitude analysis and branching fraction measurement of the decay $D^0 \to K^0_Sπ^0π^0$

An amplitude analysis of the decay $D^0 \to K_S^0 π^0 π^0$ is performed to determine the relative magnitudes and phases of different intermediate processes. The analysis uses $e^+e^-$ collision data collected at the center-of-mass energy of 3.773 GeV by the BESIII detector corresponding to an integrated luminosity of 20.3 $\rm fb^{-1}$. The absolute branching fraction of $D^0 \to K^0_S π^0 π^0$ is measured to be $(1.026 \pm 0.008_{\rm{stat.}} \pm 0.009_{\rm{syst.}}) \%$. The dominant intermediate process is $D^0 \to \bar{K}^{*}(892)^{0}(\to K^0_S π^0) π^0$, with a branching fraction of $(4.10\pm0.10_{\rm{stat.}}\pm0.07_{\rm{syst.}})\times 10^{-3}$.

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arXiv2026

Search for an isoscalar partner of the $Z_c(3900)$ in $e^+e^-\toπ^+π^-ηJ/ψ$

Using a data sample corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected at center-of-mass energies from 4.18 to 4.95 GeV with the BESIII detector, we observe the process $e^+e^-\toπ^+π^-ηJ/ψ$ with a statistical significance of $6.0 σ$, including systematic uncertainties. The isoscalar partner of the $Z_c(3900)$, denoted $X(3900)$, is searched for in the $ηJ/ψ$ final state, and no significant signal is observed. The upper limits on the product of the Born cross section $σ^{\rm Born}[e^{+}e^{-}\toπ^{+}π^{-} X(3900)$] and the branching fraction $\mathcal{B}[X(3900)\toηJ/ψ]$ are given with various assumptions for the mass and width of the $X(3900)$.

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arXiv2026

Observation and branching fraction measurements of $J/ψ\to p \bar p K^0_S K^0_S$ and $ψ(3686) \to p \bar p K^0_S K^0_S$

Using $(10.087\pm0.044)\times10^9$ $J/ψ$ events and $(2.712\pm0.014)\times10^9$ $ψ(3686)$ events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of the hadronic decays of $J/ψ\to p \bar p K^0_S K^0_S$ and $ψ(3686) \to p \bar p K^0_S K^0_S$, both with statistical significance greater than $10σ$. Their branching fractions are determined to be $\mathcal{B}(J/ψ\to p \bar p K^0_S K^0_S)=(1.60 \pm 0.02 \pm 0.09)\times10^{-5}$ and $\mathcal{B}(ψ(3686) \to p \bar p K^0_S K^0_S)=(3.93 \pm 0.24 \pm 0.34)\times10^{-6}$. The ratio of their branching fractions is $\mathcal{B}(ψ(3686) \to p \bar p K^0_S K^0_S)/\mathcal{B}(J/ψ\to p \bar p K^0_S K^0_S)=(24.6 \pm 1.5 \pm 2.1)\%$, which deviates from theoretical expectation by 4.6$σ$. Here the first uncertainties are statistical and the second systematic. We have also examined the $p\bar p$ invariant mass distributions in these decays, and no significant enhancement around the $p \bar p$ near threshold is found.

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arXiv2026

Observation of $Ξ(1530)^0$ Polarization and Determination of Its Electric and Magnetic Moments in $ψ(3686)\toΞ(1530)^0\barΞ(1530)^0$

Using the data sample of $2.7\times10^9$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII collider, we present an observation of the $Ξ(1530)^0$ polarization in the decay $ψ(3686)\toΞ(1530)^0\barΞ(1530)^0$ with a significance larger than $20σ$ compared with all other tested hypotheses. The helicity amplitudes for the process $ψ(3686)\toΞ(1530)^0\barΞ(1530)^0$ and the moduli of form factors including electric charge, magnetic dipole, electric quadrupole, and magnetic octupole are measured for the first time by performing an angular distribution analysis. Additionally, the polarization correlations between $Ξ(1530)^0$ and $\barΞ(1530)^0$ are measured.

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arXiv2026

Study of the $e^+e^-\to π^+π^-D_s^+D_s^-$ process from $\sqrt{s}$ = 4.42 to 4.95 GeV at BESIII

Based on $8.5~{\rm fb}^{-1}$ of $e^+e^-$ collision data collected at center-of-mass energies between 4.42 and 4.95 GeV with the BESIII detector at the BEPCII storage ring, we investigate the process $e^+e^-\to π^+π^-D_s^+D_s^-$. With no significant signal observed, upper limits on the Born cross sections of $e^+e^-\to π^+π^-D_s^+D_s^-$ at each energy value are determined at the 90% confidence level. Additionally, a search for intermediate charmonium-like resonances is performed in the $M(D_s^+D_s^-)$ invariant-mass spectrum, but no significant resonant structures are observed with the current statistics.

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arXiv2026

Observation of $ψ(3770)\to p\bar p$ and Measurement of Electromagnetic Form Factors of Proton at $\sqrt{s} = 3.510-4.946$ GeV

We search for possible charmonium(-like) states decaying into the $p\bar{p}$ final state by studying the Born cross sections of the $e^+e^-\to p\bar{p}$ reaction, and we determine the proton electromagnetic form factors by analyzing the proton angular distribution. The measurement is performed using a sample of $e^+e^-$ collision data collected at 47 center-of-mass energies from 3.510 to 4.946 GeV, corresponding to an integrated luminosity of 26 fb$^{-1}$, recorded by the BESIII detector collected at the BEPCII collider. The decay $ψ(3770)\to p\bar{p}$ is observed with a significance of 6.6$σ$ including systematic uncertainties. Furthermore, a structure near 4.2 GeV is observed with significances of $4.6σ$ or $4.8σ$ for the $ψ(4160)$ or $Y(4230)$ hypotheses including systematic uncertainties, respectively; these interpretations cannot presently be distinguished. In addition, the moduli of the form factor ratios $|G_{E}/G_{M}|$ and of the magnetic form factors $|G_{M}|$ are extracted by analyzing the proton polar angle distribution with higher precision at large time-like squared momentum transfer. These results provide important experimental insights into both the decay mechanisms of charmonium(-like) states in the open charm region and the internal structure of proton.

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arXiv2026

Measurement of Born cross sections for $e^+e^-\to p\bar p$ at $\sqrt{s} =3.510-4.946$ GeV

We report a measurement of the Born cross section and the effective form factor for the $e^+e^-\to p\bar{p}$ reaction at 47 center-of-mass energies between 3.510 and 4.946 GeV. The measurement is performed using the energy-scan technique and is based on data corresponding to an integrated luminosity of 26 fb$^{-1}$ collected with the BESIII detector at the BEPCII collider. For the first time, the moduli of the electromagnetic form factor ratio $|G_{E}/G_{M}|$ and of the magnetic form factor $|G_{M}|$ are determined with high precision by analyzing the distribution of the polar angle of the proton at a large timelike momentum transfer. These results provide essential insights into the nature of charmonium(-like) states above the open-charm threshold and the dynamics underlying the proton electromagnetic form factors.

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arXiv2026

Observation of an Altered $a_{0}(980)$ Line shape in $D^{+} \rightarrow π^{+}ηη$

Using $20.3~{\rm fb}^{-1}$ of $e^+e^-$ collision data collected with the BESIII detector at $\sqrt{s}=3.773~{\rm GeV}$, we perform the first amplitude analysis of the decay $D^+\toπ^+ηη$. The intermediate process $D^+\to a_0(980)^+η$, $a_0(980)^+\toπ^+η$, is observed as the only significant component in the amplitude analysis, and its branching fraction is measured to be $(3.67\pm0.12_{\rm stat}\pm0.06_{\rm syst})\times10^{-3}$. The $π^+η$ mass spectrum associated with $a_0(980)^+η$ production exhibits a line shape that differs substantially from those observed in $D_{(s)}\to a_0(980)π$ and $D^0\to a_0(980)^-e^+ν_e$ decays. We examine several conventional descriptions of the $a_0(980)$ amplitude, including Flatté, dispersively modified Flatté, $T$-matrix, and $K$-matrix parameterizations. With reference $a_0(980)$ parameters, neither these models nor their extensions including additional small resonant or non-resonant amplitudes reproduce the observed line shape satisfactorily. When the $a_0(980)$ parameters are allowed to float, satisfactory fits can be obtained, but the pole mass is driven well above the $K\bar K$ threshold, inconsistent with the near-threshold character of the $a_0(980)$. The results reveal a tension between fit quality and the physical pole position in conventional direct-production amplitude models.

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arXiv2026

First Experimental Constraint on the Scalar Current in the $D^{0(+)}\to \bar K\ell^+ν_{\ell}$ Transition

Using 20.3 fb$^{-1}$ of $e^+e^-$ collision data taken at the center-of-mass energy of $\sqrt{s}=3.773$ GeV, we report the first experimental constraint on the scalar current in the $D^{0(+)}\to \bar K\ell^+ν_{\ell}$ transitions, based on a simultaneous fit to the first measured forward-backward asymmetries and precisely determined partial decay rates. The parameters of the scalar current are determined to be ${\rm Re}(c_S^μ)=0.017\pm0.008_{\rm stat}\pm0.006_{\rm syst}$ and ${\rm Im}(c_S^μ)=\pm(0.077\pm0.011_{\rm stat}\pm0.009_{\rm syst})$, which deviates from the SM by a significance of $2.3σ$. The branching fractions of $D^{0(+)}\to \bar K\ell^+ν_\ell$, the hadronic form factor $f_+(0)$, and the modulus of the $c\to s$ CKM matrix element $|V_{cs}|$ are also determined with improved precision. In addition, lepton flavor universality is tested via the ratios of the decay rates between semi-muonic and semi-electronic decays in the full momentum transfer range and in subranges.

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arXiv2026

Precise measurements of $D^0 \to K^-\ell^+ν_\ell$ and $D^+ \to \bar K^0\ell^+ν_\ell$ decays

Using $e^+e^-$ collision data corresponding to an integrated luminosity of 20.3 fb$^{-1}$, collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we present precise measurements of $D^0 \to K^-\ell^+ν_\ell$ and $D^+ \to \bar K^0\ell^+ν_\ell$ ($\ell=e,μ$) decays. The branching fractions of $D^0\to K^-e^+ν_e$, $D^0\to K^-μ^+ν_μ$, $D^+\to \bar K^0e^+ν_e$, and $D^+\to \bar K^0μ^+ν_μ$ are measured to be $(3.548\pm0.006_{\rm stat}\pm0.017_{\rm syst}) \%$, $(3.445\pm0.007_{\rm stat}\pm0.017_{\rm syst}) \%$, $(8.928\pm0.025_{\rm stat}\pm0.050_{\rm syst}) \%$, and $(8.770\pm0.029_{\rm stat}\pm0.053_{\rm syst}) \%$, respectively. The partial decay rates of these four decays are measured with improved precision, and their forward-backward asymmetries are determined for the first time. By performing a simultaneous fit to the measured partial decay rates and the forward-backward asymmetries of $D \to \bar K\ell^+ν_{\ell}$, a search for a possible scalar current contribution in the $c\to s\ell^+ν_{\ell}$ transition is performed. The results are ${\rm Re}(c_S^μ)=0.017\pm0.008_{\rm stat}\pm0.006_{\rm syst}$ and ${\rm Im}(c_S^μ)=\pm(0.077\pm0.011_{\rm stat}\pm0.009_{\rm syst})$, corresponding to a difference from the SM with a significance of $2.3σ$. The product of the form factor $f_+(0)$ and the modulus of the $c\to s$ Cabibbo-Kobayashi-Maskawa matrix element $|V_{cs}|$ is determined to be $f_+(0)|V_{cs}|=0.7183\pm0.0007_{\rm stat}\pm0.0014_{\rm syst}$. With the inputs $|V_{cs}|=0.97349\pm0.00016$ from the Standard Model global fit or $\ffK=0.7452\pm0.0031$ from the lattice quantum chromodynamics calculation, we derive $f_+(0)=0.7383\pm0.0007_{\rm stat}\pm0.0014_{\rm syst}$ and $|V_{cs}|=0.9639\pm0.0009_{\rm stat}\pm0.0018_{\rm syst}\pm0.0040_{\rm LQCD}$.

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arXiv2026

Measurements of the absolute branching fractions of $D^0\toγ\bar K^{*0}$ and $D^0\toγϕ$

By analyzing a sample of 20.3 fb$^{-1}$ of $e^+e^-$ annihilation data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector, we have made a first measurement of the absolute branching fractions of the radiative decays $D^0\toγ\bar K^{*0}$ and $D^0\toγϕ$ to be $(3.81 \pm 0.18_{\rm stat.} \pm 0.20_{\rm syst.})\times 10^{-4}$ and $(2.51 \pm 0.44_{\rm stat.} \pm 0.11_{\rm syst.})\times 10^{-5}$, respectively. The statistical significances of $D^0\toγ\bar K^{*0}$ and $D^0\toγϕ$ are $26.8σ$ and $7.9σ$, respectively. The obtained branching fractions are consistent with the corresponding world average values. In addition, the measured $C\!P$ asymmetry $\mathcal{A}_{C\!P}(D^0\toγ\bar K^{*0})=(-0.7\pm5.0_{\rm stat.} \pm4.1_{\rm syst.})\%$ is consistent with $C\!P$ conservation.

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arXiv2026

Unexpected large relative strong phase and search for isospin breaking and $CP$ asymmetries in $J/ψ\to K^*(892)\bar K

Using a direct scan of 26 energy points near the $J/ψ$ resonance, we perform the first measurement of the relative phase $ϕ_{γ, 3g}$ between the strong and electromagnetic amplitudes in $J/ψ\to\bar K^0 K^*(892)^0+c.c.$ and $J/ψ\to K^+ K^*(892)^-+c.c.$. Unexpectedly, the phase in the neutral channel is found to be $\sim 150^\circ$, deviating from orthogonality ($90^\circ$) by 4.2$σ$ and from a relative real amplitude (0$^\circ$ or 180$^\circ$) by 10.0$σ$ or 1.6$σ$, respectively. In contrast, the charged channel phase is consistent with $\sim 180^\circ$ within 1$σ$, exhibiting model-dependent behavior. The corresponding branching fractions are consistent with the world averages but achieve better than twofold improvement in precision. The ratios between the branching fractions of $J/ψ\to\bar K^0 K^*(892)^0+c.c.$ and $J/ψ\to K^+ K^*(892)^-+c.c.$ are also measured. After subtracting the electromagnetic contribution, the corresponding strong amplitude ratios obey isospin symmetry within $1.8σ$. A search for direct $CP$ violation yields asymmetries consistent with zero.

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arXiv2026

Strong and electromagnetic amplitudes, direct $CP$ and isospin asymmetries in the decays $J/ψ\to K^0_SK^+π^-+c.c.$

Using $e^+e^-$ annihilation data collected at 26 center-of-mass energy points between 3000.00 and $3119.88~\text{MeV}$ with the BESIII detector, corresponding to a total integrated luminosity of about $440.7~\text{pb}^{-1}$, we study the cross section lineshape of $e^+e^-\to K_S^0 K^+π^-+c.c.$. The relative phases and magnitudes between $J/ψ$ strong and electromagnetic decay amplitudes are measured to be $(123.7\pm5.3)^\circ;4.31\pm0.22$ or $(-123.1\pm5.2)^\circ;4.38\pm0.22$, with corresponding branching fractions $\mathcal{B}(J/ψ\to K_S^0 K^+π^-+c.c.)=(5.17\pm0.20)$ or $(5.36\pm0.20)\times10^{-3}$. Based on a partial wave analysis, the cross sections of $e^+e^-\to\bar K^0 K^*(892)^0+c.c.$ and $e^+e^-\to K^+ K^*(892)^-+c.c.$ are obtained. For these subprocesses, the relative phases and magnitudes are determined as $(155.2\pm15.5)^{\circ};3.67\pm0.27$ or $(-154.1\pm15.5)^{\circ};3.71\pm0.25$ and $(180.1\pm31.8)^{\circ};25.06\pm2.51$, respectively. The large relative phases deviate from the orthogonality relation expected from experiment and from the assumption of purely real amplitudes by more than $3σ$. The measured branching fractions $\mathcal{B}(J/ψ\to\bar K^0 K^*(892)^0)+c.c.=(4.18\pm0.18)$ or $(4.31\pm0.19)\times10^{-3}$, $\mathcal{B}(J/ψ\to K^+ K^*(892)^-+c.c.)=(7.09\pm0.28)\times10^{-3}$ are all consistent with the world average values, but achieve better than a twofold improvement in precision. The ratios between the branching fractions of $J/ψ\to\bar K^0 K^*(892)^0+c.c.$ and $J/ψ\to\bar K^+ K^*(892)^-+c.c.$ are $\mathcal{R}_{K^*\bar{K}}=0.589\pm0.012$ or $0.612\pm0.013$. After subtracting the electromagnetic contribution, the corresponding strong amplitude ratios are $\mathcal{R}^{3g}_{K^*\bar{K}}=0.884\pm0.050$ or $0.909\pm0.044$, which deviate $2.3$ or $2.1σ$ from the unity. No evidence for direct $CP$ violation is observed.

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arXiv2026

Evidence of $ψ(3770) \to π^{0}J/ψ$

We report the first evidence for the hadronic transition $ψ(3770) \to π^0 J/ψ$ using a data sample of $20.3~\mathrm{fb}^{-1}$ collected at $\sqrt{s} = 3.773$~GeV with the BESIII detector. The $e^+ e^- \to π^{0}J/ψ$ process is observed with a statistical significance of $6.1σ$, while the significance specifically attributed to $ψ(3770) \to π^{0}J/ψ$ is $4.5σ$. We measure the dressed cross section for $e^+e^- \to π^0 J/ψ$ to be $(249 \pm 44 \pm 15)~\text{fb}$ and determine the branching fraction $\mathcal{B}(ψ(3770) \to π^0 J/ψ) = (2.08 \pm 0.36 \pm 0.21\pm 0.25) \times 10^{-5}$, where the first uncertainty is statistical, the second is systematic, and the third due to a possible interference with the $ψ(3686) \to π^{0}J/ψ$ decay. This is the first determination of this branching fraction. It lies significantly below tetraquark model predictions but aligns with calculations that incorporate meson loop effects, providing crucial insight into the isospin-violating nature of $ψ(3770)$ decays.

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arXiv2026

Study of the Magnetic Dipole Transition of $J/ψ\toγη_c$ via $η_c\to p\bar{p}$

Using $(10.087\pm0.044)\times10^9$ $J/ψ$ events collected with the BESIII detector at the $e^+e^-$ BEPCII collider, we present the first amplitude analysis of $J/ψ\toγp\bar{p}$ with the $p\bar p$ invariant mass in the $η_c$ mass region $[2.70,3.05]$~GeV/$c^2$. The product branching fraction $\mathcal{B}(J/ψ\toγη_c)\times\mathcal{B}(η_c\to p\bar{p})$ is precisely determined to be $(2.11\pm0.02_{\rm stat}\pm0.07_{\rm syst})\times10^{-5}$. Combining with the product branching fractions $\mathcal{B}(η_c\to p\bar{p})\times\mathcal{B}(η_c\to γγ)$ and $\mathcal{B}(J/ψ\toγη_c)\times\mathcal{B}(η_c\to γγ)$, the branching fractions of $\mathcal{B}(J/ψ\toγη_c)$ and $\mathcal{B}(η_c\toγγ)$ are calculated to be $(2.29\pm0.01_{\rm stat}\pm0.04_{\rm syst}\pm0.18_{\rm opbf})\%$ and $(2.28\pm0.01_{\rm stat}\pm0.04_{\rm syst}\pm0.18_{\rm opbf})\times10^{-4}$, respectively, which are consistent with the latest lattice quantum chromodynamics calculations. Here, opbf is the uncertainty from the other product branching fractions used in the calculation.

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