arXiv subjects

The BESIII Collaboration

Publications and source records attributed to The BESIII Collaboration.

At least 19 recordsLinked to original sources

arXiv2026

Measurement of $e^{+} e^{-}\to p\bar{p}$ around $\psi(2S)$ with scan method

This paper uses the data corresponding to an integrated luminosity of $495$~pb$^{-1}$ in the center-of-mass energy region from 3.58~GeV to 3.71~GeV to study the relative phase between strong and electromagnetic amplitudes in the $\psi(2S)\to p\bar{p}$ decay. The cross sections and the effective form factors around $\psi(2S)$ of proton-antiproton pairs are presented thereby filling the gap in the experimental results around the $\psi(2S)$ resonance for the first time, and the results are consistent with the previous BESIII and BaBar results. The relative phase is extracted from the cross-section line shape as $\Phi_{g,\gamma}=(105.9\pm9.4)^\circ$ or $\Phi_{g,\gamma}=(-105.3\pm9.1)^\circ$. Correspondingly, two solutions for the $\psi(2S)\to p\bar{p}$ branching fractions are obtained as $\mathcal{B}=(3.21\pm0.13)\times10^{-4}$ and $\mathcal{B}=(3.47\pm0.19)\times10^{-4}$. These results support the universality of the phase and provide new insights into its underlying mechanism.

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arXiv2025

Unraveling the structure of $\Lambda$ hyperons with polarized $\Lambda\bar{\Lambda}$ pairs

With data collected in a dedicated energy scan from 2.3864 up to 3.0800 GeV, the BESIII collaboration provides the first complete energy-dependent measurements of the $\Lambda$ electromagnetic form factors in the time-like region. By combining double-tag and single-tag events from the $e^+e^- \to \Lambda \overline\Lambda \to p\pi^-\bar{p}\pi^+$ reaction, we achieve a complete decomposition of the spin structure of the reaction at five energy points, with high statistical and systematic precision. Our data reveal that while the modulus of the ratio between the electric and magnetic form factor, $R(q^2) = |G_E(q^2)/G_M(q^2)|$, remains fairly constant across the considered energy range, the relative phase $\Delta \Phi(q^2) = \Phi_E(q^2) - \Phi_M(q^2)$ changes by more than 90$^{\mathrm{o}}$ between 2.396 and 2.6544 GeV. Using a fit to our data based on dispersion relations, the complex form factor ratio is determined as a function of $q^2$ and the preferred solution has multiple zero-crossings in the complex plane. From the derivative of the ratio at $q^2 = 0$, the root-mean-squared charge radius of the $\Lambda$ is obtained. The two most probable solutions yield a negative root-mean-squared charge radius, indicating an asymmetric charge distribution where the $ds$ quark pair lies close to the center of the $\Lambda$ hyperon.

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arXiv2024

Search for $η_c (2S)\toπ^{+}π^{-}η_{c}$ and $η_c (2S)\toπ^{+}π^{-}K^0_S K^{\pm}π^{\mp}$ decays

Based on $(27.12\pm 0.14)\times 10^{8}$ $ψ(2S)$ events collected with the BESIII detector, we search for the decay $η_c (2S) \rightarrow π^{+} π^{-} η_c$ with $η_c\rightarrow K_S^0 K^{\pm}π^{\mp}$ and $η_c\rightarrow K^{+}K^{-}π^{0}$. No significant signal is observed, and the upper limit on the product branching fraction $\mathcal{B}(ψ(2S)\rightarrow γη_{c}(2S))\times\mathcal{B}$($η_c (2S) \rightarrow π^{+} π^{-} η_c$) is determined to be $2.21\times10^{-5}$ at the 90\% confidence level. In addition, the analysis of the process $ψ(2S)\toγη_{c}(2S), η_{c}(2S)\rightarrow π^{+}π^{-}K^{0}_{S}K^{\pm}π^{\mp}$ gives a clear $η_c(2S)$ signal with a statistical significance of $10σ$ for the first time, %The product branching fraction $\mathcal{B}(ψ(2S)\rightarrow γη_{c}(2S))\times\mathcal{B}(η_{c}(2S)\rightarrow π^{+}π^{-}K^{0}_{S}Kπ) $ is measured to be $(9.31 \pm 0.72 \pm 2.77)\times 10^{-6}$, and and the branching fraction $\mathcal{B}(η_{c}(2S)\rightarrow π^{+}π^{-}K^{0}_{S}K^{\pm}π^{\mp})$ is determined to be ($1.33 \pm 0.11 \pm 0.4 \pm 0.95 $)$\times 10^{-2}$, where the first uncertainty is statistical, the second is systematic, and the third uncertainty is due to the quoted $\mathcal{B}(ψ(2S)\rightarrow γη_{c}(2S))$.

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arXiv2017

Search for the Radiative Leptonic Decay $D^{+}\to γe^{+} ν_{e}$

Using an electron-positron collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of $\sqrt{s}=3.773$ GeV with the BESIII detector, we present the first search for the radiative leptonic decay $D^{+} \rightarrow γe^{+}ν_{e}$. The analysis is performed with a double tag method. We do not observe a significant $D^{+} \rightarrow γe^{+}ν_{e}$ signal, and obtain an upper limit on the branching fraction of $D^{+} \rightarrow γe^{+}ν_{e}$ decay with the energy of radiative photon larger than 10 MeV of $3.0\times10^{-5}$ at the 90% confidence level.

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arXiv2016

Search for a light CP-odd Higgs boson in the radiative decays of J/psi

We search for a light Higgs boson $A^0$ in the fully reconstructed decay chain of $J/ψ\rightarrow γA^0$, $A^0 \rightarrow μ^+μ^-$ using $(225.0\pm2.8)\times10^6$ $J/ψ$ events collected by the BESIII experiment. The $A^0$ is a hypothetical CP-odd light Higgs boson predicted by many extensions of the Standard Model including two spin-0 doublets plus an extra singlet. We find no evidence for $A^0$ production and set $90\%$ confidence-level upper limits on the product branching fraction $\mathcal{B}(J/ψ\rightarrow γA^0) \times \mathcal{B}(A^0 \rightarrow μ^+μ^-)$ in the range of $(2.8-495.3)\times 10^{-8}$ for $0.212 \le m_{A^0} \le 3.0$ GeV/c$^2$. The new limits are $5$ times below our previous results, and the nature of the $A^0$ is constrained to be mostly singlet.

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arXiv2015

Study of $ψ(3686)\toπ^0 h_c, h_c\toγη_c$ via $η_c$ exclusive decays

The process $ψ(3686) \to π^0 h_c, h_c \to γη_c$ has been studied with a data sample of $106 \pm 4$ million $ψ(3686)$ events collected with the BESIII detector at the BEPCII storage ring. The mass and width of the $P$-wave charmonium spin-singlet state $h_c(^1P_1)$ are determined by simultaneously fitting distributions of the $π^0$ recoil mass for 16 exclusive $η_c$ decay modes. The results, $M(\hc) = 3525.31 \pm 0.11 {\rm (stat.)} \pm 0.14 {\rm (syst.)}$\,MeV/$c^2$ and $Γ(\hc) = 0.70 \pm 0.28 \pm 0.22$\,MeV, are consistent with and more precise than previous measurements. We also determine the branching ratios for the 16 exclusive $η_c$ decay modes, five of which have not been measured previously. New measurements of the $η_c$ line-shape parameters in the $E1$ transition $h_c\toγη_c$ are made by selecting candidates in the $h_c$ signal sample and simultaneously fitting the hadronic mass spectra for the 16 $η_c$ decay channels. The resulting $η_c$ mass and width values are $M(η_c) = 2984.49 \pm 1.16 \pm 0.52$\,MeV/$c^2$ and $Γ(η_c) = 36.4 \pm 3.2 \pm 1.7$\,MeV.

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arXiv2013

Study of $J/ψ\rightarrow ωp \bar{p}$ at BESIII

The decay $J/ψ\rightarrow ωp \bar{p}$ has been studied, using $225.3\times 10^{6}$ $J/ψ$ events accumulated at BESIII. No significant enhancement near the $p\bar{p}$ invariant-mass threshold (denoted as $X(p\bar{p})$) is observed. The upper limit of the branching fraction $\mathcal{B}(J/ψ\rightarrow ωX(p\bar{p}) \rightarrow ωp \bar{p})$ is determined to be $3.9\times10^{-6}$ at the 95% confidence level. The branching fraction of $J/ψ\rightarrow ωp \bar{p}$ is measured to be $\mathcal{B}(J/ψ\rightarrow ωp \bar{p}) =(9.0 \pm 0.2\ (\text{stat.})\pm 0.9\ (\text{syst.})) \times 10^{-4}$.

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arXiv2013

Evidence for η_{c}(2S) in ψ(3686) \to γK_{S}^{0}K^{\pm}π^{\mp}π^{+}π^{-}

We search for the M1 radiative transition ψ(3686) \to γη_{c}(2S) by reconstructing the exclusive η_{c}(2S) \to K_{S}^{0}K^{\pm}π^{\mp}π^{+}π^{-} decay using 1.06 \times 10^8 ψ(3686) events collected with the BESIII detector. The signal is observed with a statistical significance of greater than 4 standard deviations. The measured mass of the η_{c}(2S) is 3646.9 \pm 1.6(stat) \pm 3.6(syst) MeV/c^2, and the width is 9.9 \pm 4.8(stat) \pm 2.9(syst) MeV/c^2. The product branching fraction is measured to be B(ψ(3686) \to γη_{c}(2S)) \times B(η_{c}(2S) \to K_{S}^{0}K^{\pm}π^{\mp}π^{+}π^{-}) = (7.03 \pm 2.10(stat) \pm 0.70(syst)) \times 10^{-6}. This measurement complements a previous BESIII measurement of ψ(3686) \to γη_{c}(2S) with η_{c}(2S) \to K_{S}^{0} K^{\pm}π^{\mp} and K^{+}K^{-}π^{0}.

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arXiv2012

Observation of $η_{c}$ decay into $Σ^{+}\barΣ^{-}$ and $Ξ^{-}\barΞ^{+}$ final states

Using a data sample of $2.25\times10^{8}$ $J/ψ$ events collected with the BESIII detector, we present the first observation of the decays of $η_{c}$ mesons to $Σ^{+}\barΣ^{-}$ and $Ξ^{-}\barΞ^{+}$. The branching fractions are measured to be $(2.11\pm0.28_{\rm stat.}\pm0.18_{\rm syst.}\pm0.50_{\rm PDG})\times10^{-3}$ and $(0.89\pm0.16_{\rm stat.}\pm0.08_{\rm syst.}\pm0.21_{\rm PDG})\times10^{-3}$ for $η_{c} \to Σ^{+}\barΣ^{-}$ and $Ξ^{-}\barΞ^{+}$, respectively. These branching fractions provide important information on the helicity selection rule in charmonium-decay processes.

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arXiv2012

Observation of $e^{+}e^{-} \to ηJ/ψ$ at center-of-mass energy $sqrt{s}=4.009$ GeV

Using a 478 pb$^{-1}$ data sample collected with the BESIII detector operating at the BEPCII storage ring at a center-of-mass energy of $\sqrt{s}=4.009$ GeV, the production of $e^{+}e^{-}\to ηJψ$ is observed for the first time with a statistical significance of greater than $10σ$. The Born cross section is measured to be $(32.1\pm 2.8 \pm 1.3)$ pb, where the first error is statistical and the second systematic. Assuming the $ηJψ$ signal is from a hadronic transition of the $ψ(4040)$, the fractional transition rate is determined to be ${\cal B}(ψ(4040)\to ηJψ)=(5.2\pm 0.5\pm 0.2\pm 0.5)\times 10^{-3}$, where the first, second, and third errors are statistical, systematic, and the uncertainty from the $ψ(4040)$ resonant parameters, respectively. The production of $e^{+}e^{-} \to π^0 Jψ$ is searched for, but no significant signal is observed, and ${\cal B}(ψ(4040)\to π^0 Jψ) < 2.8 \times 10^{-4}$ is obtained at the 90% confidence level.

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arXiv2012

Search for hadronic transition $χ_{cJ}\toη_{c}π^{+}π^{-}$ and observation of $χ_{cJ}\to K\bar{K}πππ$

Hadronic transitions of $χ_{cJ}\to η_{c}π^{+}π^{-}$ (J=0, 1, 2) are searched for using a sample of $1.06\times 10^{8}$ $ψ(3686)$ events collected with the BESIII detector at the BEPCII storage ring. The $\etac$ is reconstructed with $K_{S}^{0}K^{+}π^{-}+c.c.$ and $K^{+}K^{-}π^{0}$ final states. No signals are observed in any of the three $χ_{cJ}$ states in either $\etac$ decay mode. At the 90% confidence level, the upper limits are determined to be $\BR(χ_{c0}\to η_{c}π^{+}π^{-})<0.07%$, $\BR(χ_{c1}\to η_{c}π^{+}π^{-})<0.32%$, and $\BR(χ_{c2}\to η_{c}π^{+}π^{-})<0.54%$. The upper limit of $\BR(χ_{c1}\to η_{c}π^{+}π^{-}$ is lower than the existing theoretical prediction by almost an order of magnitude. The branching fractions of $χ_{cJ}\to K_{S}^{0}K^{+}π^{-}π^{+}π^{-}+c.c.$, $K^{+}K^{-}π^{+}π^{-}π^{0}$, $ωK^{+}K^{-}$ and $ϕπ^{+}π^{-}π^{0}$ (J=0, 1, 2) are measured for the first time.

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arXiv2011

Search for $η_{c}^{\prime}$ decays into vector meson pairs

The processes $\etacpto ρ^{0}ρ^{0}$, $K^{*0}\bar{K}^{*0}$, and $ϕϕ$ are searched for using a sample of $1.06 \times 10^8$ $\psip$ events collected with the BESIII detector at the BEPCII collider. No signals are observed in any of the three final states. The upper limits on the decay branching fractions are determined to be $\mathcal{B}(\etacptoρ^{0}ρ^{0})<3.1\times10^{-3}$, $\mathcal{B}(\etacpto K^{*0}\bar{K}^{*0})<5.4 \times10^{-3}$, and $\mathcal{B}(\etacptoϕϕ)<2.0\times10^{-3}$ at the 90% confidence level. The upper limits are lower than the existing theoretical predictions.

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arXiv2011

Search for CP and $P$ violating pseudoscalar decays into $ππ$

Using a sample of $(225.2\pm 2.8)\times 10^6$ $J/ψ$ events collected with the Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider, CP and $P$ violating decays of $η$, $η'$ and $\etac$ into $π^+π^-$ and $π^0 π^0$ are searched for in $\jpsi$ radiative decays. No significant $η$, $η'$ or $\etac$ signal is observed, and 90% confidence level upper limits of $\BR(η\to π^+π^-)<3.9\times 10^{-4}$, $\BR(η' \to π^+π^-)<5.5\times 10^{-5}$, $\BR(\etac \to π^+π^-)<1.3\times 10^{-4}$, $\BR(η\to π^0 π^0)<6.9\times 10^{-4}$, $\BR(η' \to π^0 π^0)<4.5\times 10^{-4}$ and $\BR(\etac \to π^0 π^0)<4.2\times 10^{-5}$ are obtained.

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arXiv2011

Study of a0(980)--f0(980) mixing

Using samples of 2.25*10^8 J/psi events and 1.06*10^8 psi' events collected with the BES III detector, we study the f0(980) to a0(980) and a0(980) to f0(980) transitions in the processes J/psi --> phi f0(980) --> phi a0(980) and chi_c1 --> pi^0 a0(980) --> pi^0 f0(980), respectively. Evidence for f0(980) --> a0(980) is found with a significance of 3.4 sigma, while in the case of a0(980) --> f0(980) transition, the significance is 1.9 sigma. Measurements and upper limits of both branching ratios and mixing intensities are determined.

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arXiv2011

Measurement of the Matrix Element for the Decay $η^{\prime} \to ηπ^+π^-$

The Dalitz plot of $η^{\prime} \to ηπ^+ π^-$ decay is studied using $(225.2\pm2.8)\times 10^6$ $\jpsi$ events collected with the BESIII detector at the BEPCII $e^+e^-$ collider. With the largest sample of $η^{\prime}$ decays to date, the parameters of the Dalitz plot are determined in a generalized and a linear representation. Also the branching fraction of $\jpsi \to γη^{\prime}$ is determined to be $(4.84\pm0.03\pm0.24)\times 10^{-3}$, where the first error is statistical and the second systematic.

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arXiv2010

Evidence for psi' decays into gamma pi^0 and gamma eta

The decays psi'->gamma pi^0, gamma eta and gamma eta' are studied using data collected with the BESIII detector at the BEPCII e^+e^- collider. Processes psi'->gamma pi^0 and psi'->gamma eta are observed for the first time with signal significances of 4.6 sigma and 4.3 sigma, respectively. The branching fractions are determined to be: B(psi'->gamma pi^0)=(1.58+-0.40+-0.13)x10^{-6}, B(psi'->gamma eta)=(1.38+-0.48+-0.09)x10^{-6}, and B(psi'->gamma eta')=(126+-3+-8) x 10^{-6}, where the first errors are statistical and the second ones systematic.

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arXiv2010

Measurements of h_c(^1P_1) in psi' Decays

We present measurements of the charmonium state $h_c(^1P_1)$ made with 106M $ψ'$ events collected by BESIII at BEPCII. Clear signals are observed for $ψ'\toπ^0 h_c$ with and without the subsequent radiative decay $h_c\toγη_c$. First measurements of the absolute branching ratios $\mathcal{B}(ψ' \toπ^0 h_c) = (8.4 \pm 1.3 \pm 1.0) \times 10^{-4}$ and $\mathcal{B}(h_c \to γη_c) = (54.3 \pm 6.7 \pm5.2)%$ are presented. A statistics-limited determination of the previously unmeasured $h_c$ width leads to an upper limit $Γ(h_c)<1.44 $MeV (90% confidence). Measurements of $M(h_c) = 3525.40 \pm 0.13 \pm 0.18 $MeV/$c^2$ and $\mathcal{B}(ψ'\to π^0 h_c) \times \mathcal{B}(h_c \to γη_c) = (4.58 \pm 0.40 \pm 0.50) \times 10^{-4}$ are consistent with previous results.

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arXiv2010

Branching fraction measurements of χ_{c0} and χ_{c2} to π^0π^0 and ηη

Using a sample of 1.06 \times 10^8 ψ^{\prime} decays collected by the BESIII detector, χ_{c0} and χ_{c2} decays into π^0π^0 and ηηare studied. The branching fraction results are Br(χ_{c0}\toπ^0π^0)=(3.23\pm 0.03\pm0.23 \pm 0.14)\times 10^{-3}, Br(χ_{c2}\toπ^0π^0)=(8.8\pm 0.2\pm 0.6\pm0.4)\times 10^{-4}, Br(χ_{c0}\toηη)=(3.44\pm 0.10\pm0.24 \pm0.2)\times 10^{-3}, and Br(χ_{c2}\toηη)=(6.5\pm 0.4\pm 0.5\pm 0.3)\times 10^{-4}, where the uncertainties are statistical, systematic due to this measurement, and systematic due to the branching fractions of ψ^{\prime}\toγχ_{cJ}, respectively. The results provide information on the decay mechanism of χ_c states into pseudoscalars.

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