34 Search Results

Using a sample of ( 2712.4 ± 14.3 ) × 10 6     ψ ( 3686 ) events collected with the BESIII detector, we perform a search for the isospin-violating decays χ c J → Λ Σ ¯   0 + c . c . ( J = 0 , 1 , 2 ) and η c → Λ Σ ¯   0 + c . c . No significant signal for χ c J or η c is observed in the Λ Σ ¯   0 invariant mass distribution. The upper limits on the branching fractions at the 90% confidencemore » level are set to be B ( χ c 0 → Λ Σ ¯   0 + c . c . ) < 1.5 × 10 − 6 , B ( χ c 1 → Λ Σ ¯   0 + c . c . ) < 1.6 × 10 − 6 , B ( χ c 2 → Λ Σ ¯   0 + c . c . ) < 1.7 × 10 − 6 , and B ( η c → Λ Σ ¯   0 + c . c . ) < 6.2 × 10 − 5 for the first time.« less

The first direct measurement of the relative phase between the strong and electromagnetic amplitudes for a J/ψ decaying into a vector-pseudoscalar final state is performed using 26 energy points of e⁺e⁻ annihilation data between 3.00 GeV and 3.12 GeV. The data sets were collected by the BESIII detector with a total integrated luminosity of 452 pb⁻¹. By investigating the interference pattern in the cross section lineshape of e⁺e⁻ → ϕη, the relative phase between the strong and electromagnetic amplitudes of J/ψ decay is determined to be within [133°, 228°] at 68% confidence level.

We present the first amplitude analysis and branching fraction measurement of the decay $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$ , using $e^{+}{e}^{-}$ collision data collected with the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV corresponding to an integrated luminosity of $7.33{\mathrm{fb}}^{-1}$ , and report the first observation of the pure $W$ -annihilation decay $more »$ D s + → ω ρ + with a branching fraction of $(0.99\pm 0.08_{\mathrm{stat}}{{}_{-0.07}^{+0.05}}_{\mathrm{syst}})\%$ . In comparison to the low significance of the $\mathcal{D}$ wave in the decay $D_s^{+}\to \varphi {\rho }^{+}$ , the dominance of the $\mathcal{D}$ wave over the $\mathcal{S}$ and $\mathcal{P}$ waves, with a fraction of $(51.85\pm 7.28_{\mathrm{stat}}{{}_{-7.90}^{+4.83}}_{\mathrm{syst}})\%$ observed in the decay $D_s^{+}\to \omega {\rho }^{+}$ , provides crucial information for the “polarization puzzle,” as well as for the understanding of charm meson decays. The branching fraction of $D_s^{+}\to {\pi }^{+}{\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$ is measured to be $(4.41\pm 0.15_{\mathrm{stat}}\pm 0.13_{\mathrm{syst}})\%$ . Moreover, the branching fraction of $D_s^{+}\to \varphi {\rho }^{+}$ is measured to be $(3.98\pm 0.33_{\mathrm{stat}}{{}_{-0.19}^{+0.21}}_{\mathrm{syst}})\%$ , and the $R_{\varphi }=\mathcal{B}(\varphi \to {\pi }^{+}{\pi }^{-}{\pi }^0)/\mathcal{B}(\varphi \to K^{+}{K}^{-})$ is determined to be ( $0.222\pm 0.019_{\mathrm{stat}}{{}_{-0.016}^{+0.016}}_{\mathrm{syst}}$ ), which is consistent with the previous measurement based on charm meson decays, but deviates from the results from $e^{+}{e}^{-}$ annihilation and $K-N$ scattering experiments by more than $3\sigma$ . Published by the American Physical Society 2025« less

Using $20.3{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector operating at the BEPCII collider, the branching fractions of three hadronic charm meson decays, $D^{+}\to \varphi {\pi }^{+}{\pi }^{+}{\pi }^{-}$ , $D^{+}\to K_S^0{K}^{+more »}$ π + π − π 0 , and $D^{+}\to K_S^0{K}^{+}\omega$ , are measured for the first time to be $(0.54\pm 0.19\pm 0.02)\times {10}^{-4}$ , $(2.51\pm 0.34\pm 0.14)\times {10}^{-4}$ , and $(2.02\pm 0.35\pm 0.10)\times {10}^{-4}$ , respectively. Futhermore, the branching fractions of $D^{+}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^{+}{\pi }^{-}$ and $D^{+}\to K_S^0{K}^{+}\eta$ are measured with improved precision, yielding values of $(0.66\pm 0.11\pm 0.03)\times {10}^{-4}$ and $(2.27\pm 0.22\pm 0.05)\times {10}^{-4}$ , respectively. Published by the American Physical Society 2025« less

Using a dataset of $(27.12\pm 0.14)\times {10}^8\psi \left(3686\right)$ events collected by the BESIII detector operating at the BEPCII collider, we report the first observation of the decay $\psi \left(3686\right)\to {\mathrm{\Sigma }}^0{\overline{\mathrm{\Sigma }}}^0\omega$ with a statistical significance of $8.9\sigma$ . The measured branching fraction is $(1.24\pm 0.16_{\mathrm{stat}}\pm 0.11_{\mathrm{sys}})\times {10}^{more »}$ − 5 , where the first uncertainty is statistical and the second is systematic. Additionally, we investigate potential intermediate states in the invariant mass distributions of ${\mathrm{\Sigma }}^0\omega$ , ${\overline{\mathrm{\Sigma }}}^0\omega$ and ${\mathrm{\Sigma }}^0{\overline{\mathrm{\Sigma }}}^0$ . A hint of a resonance is observed in the invariant mass distribution of $M_{{\mathrm{\Sigma }}^0\left({\overline{\mathrm{\Sigma }}}^0\right)\omega }$ , located around $2.06\mathrm{GeV}/c^2$ , with a significance of $2.5\sigma$ . Published by the American Physical Society 2025« less

Using $7.93{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we present an analysis of the decay $D^0\to \eta {\pi }^{-}{e}^{+}{\nu }_e$ . The branching fraction of the decay $D^{more »}$ 0 → a 0 ( 980 ) − e + ν e with $a_0(980{)}^{-}\to \eta {\pi }^{-}$ is measured to be $(0.86\pm 0.17_{\mathrm{stat}}\pm 0.05_{\mathrm{syst}})\times {10}^{-4}$ . The decay dynamics of this process is studied with a single-pole parametrization of the hadronic form factor and the Flatté formula describing the $a_0\left(980\right)$ line shape in the differential decay rate. The product of the form factor $f_{+}^{a_0}\left(0\right)$ and the Cabibbo-Kobayashi-Maskawa matrix element $\left|V_{cd}\right|$ is determined for the first time with the result $f_{+}^{a_0}\left(0\right)\left|V_{cd}\right|=0.126\pm 0.013_{\mathrm{stat}}\pm 0.003_{\mathrm{syst}}$ . Published by the American Physical Society 2025« less

Using $(2712.4\pm 14.3)\times {10}^6\psi \left(3686\right)$ events collected with the BESIII detector at the BEPCII collider, the decay ${\eta }_c\to \gamma \gamma$ in $J/\psi \to \gamma {\eta }_c$ is observed. We determine the product branching fraction $\mathcal{B}(J/\psi \to \gamma {\eta }_c)\times \mathcal{B}more »$ ( η c → γ γ ) = ( 5.23 ± 0.2 6 stat ± 0.3 0 syst ) × 10 − 6 . This result is consistent with the lattice QCD calculation $(5.34\pm 0.16)\times {10}^{-6}$ from HPQCD in 2023. By using the world-average values of $\mathcal{B}(J/\psi \to \gamma {\eta }_c)$ and the total decay width of ${\eta }_c$ , the partial decay width $\mathrm{\Gamma }({\eta }_c\to \gamma \gamma )$ is determined to be $(11.30\pm 0.56_{\mathrm{stat}}\pm 0.66_{\mathrm{syst}}\pm 1.14_{\mathrm{ref}})\mathrm{keV}$ , which deviates from the corresponding world-average value by $3.4\sigma$ . Published by the American Physical Society 2025« less

By analyzing $7.93{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector operated at the BEPCII collider, we report the observation of the semimuonic decays of $D^{+}\to {\overline{K}}_1(1270{)}^0{\mu }^{+}{\nu }_{\mu }$ and $D^0\to K_1(1270{)}^{-}{\mu }^{+}$ ν μ with statistical significances of $12.5\sigma$ and $6.0\sigma$ , respectively. Their decay branching fractions are determined to be $\mathcal{B}[D^{+}\to {\overline{K}}_1(1270{)}^0{\mu }^{+}{\nu }_{\mu }]=(2.36\pm 0.20_{-0.27}^{+0.18}\pm 0.48)\times {10}^{-3}$ and $\mathcal{B}[D^0\to K_1(1270{)}^{-}{\mu }^{+}{\nu }_{\mu }]=(0.78\pm 0.11_{-0.09}^{+0.05}\pm 0.15)\times {10}^{-3}$ , where the first and second uncertainties are statistical and systematic, respectively, and the third originates from the input branching fraction of ${\overline{K}}_1(1270{)}^0\to K^{-}{\pi }^{+}{\pi }^0$ or $K_1(1270{)}^{-}\to K^{-}{\pi }^{+}{\pi }^{-}$ . Combining our branching fractions with the previous measurements of $\mathcal{B}[D^{+}\to {\overline{K}}_1(1270{)}^0{e}^{+}{\nu }_e]$ and $\mathcal{B}[D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e]$ , we determine the branching fraction ratios to be $\mathcal{B}[D^{+}\to {\overline{K}}_1(1270{)}^0{\mu }^{+}{\nu }_{\mu }]/\mathcal{B}[D^{+}\to {\overline{K}}_1\left(1270{)}^0{e}^{+}{\nu }_e\right]=1.03\pm {0.14}_{-0.15}^{+0.11}$ and $\mathcal{B}[D^0\to K_1(1270{)}^{-}{\mu }^{+}{\nu }_{\mu }]/\mathcal{B}[D^0\to K_1\left(1270{)}^{-}{e}^{+}{\nu }_e\right]=0.74\pm {0.13}_{-0.13}^{+0.08}$ . Using the branching fractions measured in this work and the world-average lifetimes of the $D^{+}$ and $D^0$ mesons, we determine the semimuonic partial decay width ratio to be $\mathrm{\Gamma }[D^{+}\to {\overline{K}}_1(1270{)}^0{\mu }^{+}{\nu }_{\mu }]/\mathrm{\Gamma }[D^0\to K_1\left(1270{)}^{-}{\mu }^{+}{\nu }_{\mu }\right]=1.22\pm {0.10}_{-0.09}^{+0.06}$ , which is consistent with unity as predicted by isospin conservation. Published by the American Physical Society 2025« less

Using a sample of $(10087\pm 44)\times {10}^{6}J/\psi$ events accumulated with the BESIII detector, we analyze the decays $\eta \to {\pi }^{+}{\pi }^{-}{l}^{+}{l}^{-}$ ( $l=e$ or $\mu$ ) via the process $J/\psi \to \gamma \eta$ . The branching fraction of $\eta \to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ is measuredmore » to be $\mathcal{B}(\eta \to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-})=(3.07\pm 0.12_{\mathrm{stat}}\pm 0.19_{\mathrm{syst}})\times {10}^{-4}$ . No signal events are observed for the $\eta \to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-}$ decay, leading to an upper limit on the branching fraction of $\mathcal{B}(\eta \to {\pi }^{+}{\pi }^{-}{\mu }^{+}{\mu }^{-})<4.0\times {10}^{-7}$ at the 90% confidence level. Furthermore, the $CP$ -violation asymmetry parameter is found to be ${\mathcal{A}}_{CP}(\eta \to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-})=(-4.04\pm 4.69_{\mathrm{stat}}\pm 0.14_{\mathrm{syst}})\%$ , showing no evidence of $CP$ -violation with current statistics. Additionally, we extract the transition form factor from the decay amplitude of $\eta \to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ . Finally, axionlike particles are searched for via the decay $\eta \to {\pi }^{+}{\pi }^{-}a,a\to e^{+}{e}^{-}$ , and upper limits on this branching fraction relative to that of $\eta \to {\pi }^{+}{\pi }^{-}{e}^{+}{e}^{-}$ are presented as a function of the axionlike particle mass in the range $5–200\mathrm{MeV}/c^2$ . Published by the American Physical Society 2025« less

Using $e^{+}{e}^{-}$ collision data corresponding to an integrated luminosity of $19{\mathrm{fb}}^{-1}$ collected by the BESIII detector at center-of-mass energies ranging from 4.13 to 4.70 GeV, we report the first evidence for a new excited ${\mathrm{\Omega }}^{-}$ hyperon, the $\mathrm{\Omega }(2109{)}^{-}$ , through the process $e^{+}more »$ e − → Ω ( 2109 ) − Ω ¯ + + c .     c . with a significance of $4.1\sigma$ . The mass and width of $\mathrm{\Omega }(2109{)}^{-}$ are measured to be $2108.5\pm {5.2}_{\mathrm{stat}}\pm {0.9}_{\mathrm{syst}}\mathrm{MeV}/c^2$ and $18.3\pm {16.4}_{\mathrm{stat}}\pm {5.7}_{\mathrm{syst}}\mathrm{MeV}$ , respectively. We also present evidence for a new production mechanism for the previously identified $\mathrm{\Omega }(2012{)}^{-}$ via the process $e^{+}{e}^{-}\to \mathrm{\Omega }(2012{)}^{-}{\overline{\mathrm{\Omega }}}^{+}+\mathrm{c}.\mathrm{c}.$ with a significance of $3.5\sigma$ . Published by the American Physical Society 2025« less