Search

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

Using a sample of 106 million $\psi (3686)$ decays, the branching fractions of $\psi (3686)\to \gamma {\chi }_{c0}$, $\psi (3686)\to \gamma {\chi }_{c1}$, and $\psi (3686)\to \gamma {\chi }_{c2}$ are measured with improved precision to be $(9.389\pm 0.014\pm 0.332)\%$, $(9.905\pm 0.011\pm 0.353)\%$, and $(9.621\pm 0.013\pm 0.272)\%$, respectively, where the first uncertainties are statistical and the second ones are systematic. The product branching fractions of $\psi (3686)\to \gamma {\chi }_{c1},{\chi }_{c1}\to \gamma J/\psi$ and $\psi (3686)\to \gamma {\chi }_{c2},{\chi }_{c2}\to \gamma J/\psi$ and the branching fractions of ${\chi }_{c1}\to \gamma J/\psi$ and ${\chi }_{c2}\to \gamma J/\psi$ are also presented.

Using a sample of $1.31\times {10}^{9}J/\psi$ events collected with the BESIII detector at the BEPCII collider, we study the decays of $J/\psi \to K_S{K}_L$ and $K_S{K}_S$. The branching fraction of $J/\psi \to K_S{K}_L$ is determined to be $\mathcal{B}(J/\psi \to K_S{K}_L)=(1.93\pm 0.01(\mathrm{stat})\pm 0.05(\mathrm{syst}))\times {10}^{-4}$, which significantly improves on previous measurements. No clear signal is observed for the $J/\psi \to K_S{K}_S$ process, and the upper limit at the 95% confidence level for its branching fraction is determined to be $\mathcal{B}(J/\psi \to K_S{K}_S)<1.4\times {10}^{-8}$, which improves on the previous searches by 2 orders in magnitude and reaches the order of the Einstein-Podolsky-Rosen expectation.

We present the first search for the rare decay of ${\eta }^{\prime }$ into $K^{\pm }{\pi }^{\mp }$ in $J/\psi \to \varphi {\eta }^{\prime }$, using a sample of $1.3\times 10^{9}J/\psi$ events collected with the BESIII detector. No significant signal is observed, and the upper limit at the 90% confidence level for the ratio $\frac{\mathcal{B}({\eta }^{\prime }\to K^{\pm }{\pi }^{\mp })}{\mathcal{B}({\eta }^{\prime }\to \gamma {\pi }^{+}{\pi }^{-})}$ is determined to be $1.3\times 10^{-4}$. In addition, we report the measurement of the branching fraction of $J/\psi \to \varphi {\eta }^{\prime }$ to be $[5.10\pm 0.03(\text{stat})\pm 0.32(\text{syst})]\times 10^{-4}$, which agrees with previous results from BESII.

The process $e^{+}{e}^{-}\to p{K}_S^0\overline{n}{K}^{-}+\mathrm{c}.\mathrm{c}.$ and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of $7.4{\mathrm{fb}}^{-1}$. The Born cross section of $e^{+}{e}^{-}\to p{K}_S^0\overline{n}{K}^{-}+\mathrm{c}.\mathrm{c}.$ is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the $p{K}^{-}$, $n{K}_S^0$, $p{K}_S^0$, $n{K}^{+}$, $p\overline{n}$, or $K_S^0{K}^{-}$ invariant mass distributions except for $\mathrm{\Lambda }(1520)$. The Born cross sections of $e^{+}{e}^{-}\to \mathrm{\Lambda }(1520)\overline{n}{K}_S^0+\mathrm{c}.\mathrm{c}.$ and $e^{+}{e}^{-}\to \mathrm{\Lambda }(1520)\overline{p}{K}^{+}+\mathrm{c}.\mathrm{c}.$ are measured, and the 90% confidence level upper limits on the Born cross sections of $e^{+}{e}^{-}\to \mathrm{\Lambda }(1520)\overline{\mathrm{\Lambda }}(1520)$ are determined at the seven center-of-mass energies. There is an evident difference in line shape and magnitude of the measured cross sections between $e^{+}{e}^{-}\to \mathrm{\Lambda }(1520)(\to p{K}^{-})\overline{n}{K}_S^0$ and $e^{+}{e}^{-}\to p{K}^{-}\overline{\mathrm{\Lambda }}(1520)(\to \overline{n}{K}_S^0)$.

Based on $(2712.4\pm 14.3)\times {10}^6\psi (3686)$ events, we investigate four hadronic decay modes of the $P$-wave charmonium spin-singlet state $h_c{(}^1{P}_1)\to h^{+}{h}^{-}{\pi }^0/\eta$ ($h=\pi$ or $K$) via the process $\psi (3686)\to {\pi }^0{h}_c$ at BESIII. The $h_c\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decay is observed with a significance of $9.6\sigma$ after taking into account systematic uncertainties. Evidences for $h_c\to K^{+}{K}^{-}{\pi }^0$ and $h_c\to K^{+}{K}^{-}\eta$ are found with significances of $3.5\sigma$ and $3.3\sigma$, respectively, after considering the systematic uncertainties. The branching fractions of these decays are measured to be $\mathcal{B}(h_c\to {\pi }^{+}{\pi }^{-}{\pi }^0)=(1.36\pm 0.16\pm 0.14)\times {10}^{-3}$, $\mathcal{B}(h_c\to K^{+}{K}^{-}{\pi }^0)=(3.26\pm 0.84\pm 0.36)\times {10}^{-4}$, and $\mathcal{B}(h_c\to K^{+}{K}^{-}\eta )=(3.13\pm 1.08\pm 0.38)\times {10}^{-4}$, where the first uncertainties are statistical and the second are systematic. No significant signal of $h_c\to {\pi }^{+}{\pi }^{-}\eta$ is found, and the upper limit of its decay branching fraction is determined to be $\mathcal{B}(h_c\to {\pi }^{+}{\pi }^{-}\eta )<4.0\times {10}^{-4}$ at the 90% confidence level.

Using a data sample of $448\times {10}^6\psi (3686)$ events collected with the BESIII detector operating at the BEPCII storage ring, the decays $\psi (3686)\to \gamma \eta$ and $\psi (3686)\to \gamma {\pi }^0$ are observed with a statistical significance of $7.3\sigma$ and $6.7\sigma$, respectively. The branching fractions are measured to be $\mathcal{B}(\psi (3686)\to \gamma \eta )=(0.85\pm 0.18\pm 0.05)\times {10}^{-6}$ and $\mathcal{B}(\psi (3686)\to \gamma {\pi }^0)=(0.95\pm 0.16\pm 0.05)\times {10}^{-6}$. In addition, we measure the branching fraction of $\psi (3686)\to \gamma {\eta }^{\prime }$ to be $\mathcal{B}(\psi (3686)\to \gamma {\eta }^{\prime })=(125.1\pm 2.2\pm 6.2)\times {10}^{-6}$, which represents an improvement of precision over previous results.

By analyzing $(448.1\pm 2.9)\times 10^6$ $\psi (3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decays of ${\chi }_{cJ}\to 4K_S^0$ ($J=0$, 1, 2) are observed for the first time with statistical significances of $26.5\sigma$, $5.9\sigma$ and $11.4\sigma$, respectively. The product branching fractions of $\psi (3686)\to \gamma {\chi }_{cJ}$, ${\chi }_{cJ}\to 4K_S^0$ are presented, and the branching fractions of ${\chi }_{cJ}\to 4K_S^0$ decays are determined to be ${\mathcal{B}}_{{\chi }_{c0}\to 4K_S^0}=(5.76\pm 0.34\pm 0.38)\times 10^{-4}$, ${\mathcal{B}}_{{\chi }_{c1}\to 4K_S^0}=(0.35\pm 0.09\pm 0.03)\times 10^{-4}$ and ${\mathcal{B}}_{{\chi }_{c2}\to 4K_S^0}=(1.14\pm 0.15\pm 0.08)\times 10^{-4}$, where the first uncertainties are statistical and the second are systematic, respectively.

Based on $2.93{\mathrm{fb}}^{-1}$ $e^{+}{e}^{-}$ collision data taken at center-of-mass energy of 3.773 GeV by the BESIII detector, we report searches for the singly Cabibbo-suppressed decays $D^{+}\to \omega {\pi }^{+}$ and $D^0\to \omega {\pi }^0$. A double tag technique is used to measure the absolute branching fractions $\mathcal{B}(D^{+}\to \omega {\pi }^{+})=(2.79\pm 0.57\pm 0.16)\times {10}^{-4}$ and $\mathcal{B}(D^0\to \omega {\pi }^0)=(1.17\pm 0.34\pm 0.07)\times {10}^{-4}$, with statistical significances of $5.5\sigma$ and $4.1\sigma$, where the first and second uncertainties are statistical and systematic, respectively.

Using $1.06\times 10^8$ $\psi (3686)$ events recorded in $e^{+}{e}^{-}$ collisions at $\sqrt{s}=3.686\mathrm{GeV}$ with the BESIII at the BEPCII collider, we present searches for $C$-parity violation in $J/\psi \to \gamma \gamma$ and $\gamma \varphi$ decays via $\psi (3686)\to J/\psi {\pi }^{+}{\pi }^{-}$. No significant signals are observed in either channel. Upper limits on the branching fractions are set to be $\mathcal{B}(J/\psi \to \gamma \gamma )<2.7\times 10^{-7}$ and $\mathcal{B}(J/\psi \to \gamma \varphi )<1.4\times 10^{-6}$ at the 90% confidence level. The former is one order of magnitude more stringent than the previous upper limit, and the latter represents the first limit on this decay channel.

By using a $2.92{\mathrm{fb}}^{-1}$ data sample taken at $\sqrt{s}=3.773\mathrm{GeV}$ with the BESIII detector operating at the BEPCII collider, we search for the radiative transitions $\psi (3770)\to \gamma {\eta }_c$ and $\gamma {\eta }_c(2S)$ through the hadronic decays ${\eta }_c({\eta }_c(2S))\to K_S^0{K}^{\pm }{\pi }^{\mp }$. No significant excess of signal events above background is observed. We set upper limits at a 90% confidence level for the product branching fractions to be $\mathcal{B}(\psi (3770)\to \gamma {\eta }_c)\times \mathcal{B}({\eta }_c\to K_S^0{K}^{\pm }{\pi }^{\mp })<1.6\times {10}^{-5}$ and $\mathcal{B}(\psi (3770)\to \gamma {\eta }_c(2S))\times \mathcal{B}({\eta }_c(2S)\to K_S^0{K}^{\pm }{\pi }^{\mp })<5.6\times {10}^{-6}$. Combining our result with world-average values of $\mathcal{B}({\eta }_c({\eta }_c(2S))\to K_S^0{K}^{\pm }{\pi }^{\mp })$, we find the branching fractions $\mathcal{B}(\psi (3770)\to \gamma {\eta }_c)<6.8\times {10}^{-4}$ and $\mathcal{B}(\psi (3770)\to \gamma {\eta }_c(2S))<2.0\times {10}^{-3}$ at a 90% confidence level.

Using a $3.19{\mathrm{fb}}^{-1}$ data sample collected at the $\sqrt{s}=4.178\mathrm{GeV}$ with the BESIII detector, we search for the rare decay $D_s^{+}\to p\overline{p}{e}^{+}{\nu }_e$. No significant signal is observed, and an upper limit of $\mathcal{B}(D_s^{+}\to p\overline{p}{e}^{+}{\nu }_e)<2.0\times {10}^{-4}$ is set at the 90% confidence level. This measurement is useful input in understanding the baryonic transition of $D_s^{+}$ mesons.

Using a sample of $1.31\times {10}^{9}J/\psi$ events collected with the BESIII detector, we perform a study of $J/\psi \to \gamma \eta \eta {\eta }^{\prime }$ to search for the $X(2370)$ and ${\eta }_c$ in the $\eta \eta {\eta }^{\prime }$ invariant mass distribution. No significant signal for the $X(2370)$ is observed, and we set an upper limit for the product branching fraction of $\mathcal{B}(J/\psi \to \gamma X(2370)·\mathcal{B}(X(2370)\to \eta \eta {\eta }^{\prime })<9.2\times {10}^{-6}$ at the 90% confidence level. A clear ${\eta }_c$ signal is observed for the first time, yielding a product branching fraction of $\mathcal{B}(J/\psi \to \gamma {\eta }_c)·\mathcal{B}({\eta }_c\to \eta \eta {\eta }^{\prime })=(4.86\pm 0.62(\mathrm{stat})\pm 0.45(\mathrm{sys}))\times {10}^{-5}$.

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

We report on a study of the isospin-violating and isospin-conserving decays of the $J/\psi$ and ${\psi }^{\prime }$ charmonium state to $\Lambda \overline{\Lambda }{\pi }^0$ and $\Lambda \overline{\Lambda }\eta$, respectively. The data are based on 225 million $J/\psi$ and 106 million ${\psi }^{\prime }$ events that were collected with the BESIII detector. The most accurate measurement of the branching fraction of the isospin-violating process $J/\psi \to \Lambda \overline{\Lambda }{\pi }^0$ is obtained, and the isospin-conserving processes $J/\psi \to \Lambda \overline{\Lambda }\eta$ and ${\psi }^{\prime }\to \Lambda \overline{\Lambda }\eta$ are observed for the first time. The branching fractions are measured to be $\mathcal{B}(J/\psi \to \Lambda \overline{\Lambda }{\pi }^0)=(3.78\pm {0.27}_{\mathrm{stat}}\pm {0.30}_{\mathrm{sys}})\times {10}^{-5}$, $\mathcal{B}(J/\psi \to \Lambda \overline{\Lambda }\eta )=(15.7\pm {0.80}_{\mathrm{stat}}\pm {1.54}_{\mathrm{sys}})\times {10}^{-5}$ and $\mathcal{B}({\psi }^{\prime }\to \Lambda \overline{\Lambda }\eta )=(2.48\pm {0.34}_{\mathrm{stat}}\pm {0.19}_{\mathrm{sys}})\times {10}^{-5}$. No significant signal events are observed for ${\psi }^{\prime }\to \Lambda \overline{\Lambda }{\pi }^0$ decay resulting in an upper limit of the branching fraction of $\mathcal{B}({\psi }^{\prime }\to \Lambda \overline{\Lambda }{\pi }^0)<0.29\times {10}^{-5}$ at the 90% confidence level. The two-body decay of $J/\psi \to \Sigma (1385{)}^0\overline{\Lambda }+\mathrm{c}.\mathrm{c}.$ is searched for, and the upper limit is $B(J/\psi \to \Sigma (1385{)}^0\overline{\Lambda }+\mathrm{c}.\mathrm{c}.)<0.82\times {10}^{-5}$ at the 90% confidence level.

Based on a sample of $2.25\times {10}^{8}J/\psi$ events taken with the BESIII detector at the BEPCII collider, we present the results of a study of the decay $J/\psi \to \eta \varphi {\pi }^{+}{\pi }^{-}$. The $Y(2175)$ resonance is observed in the invariant mass spectrum of $\varphi f_0(980)$ with a statistical significance of greater than $10\sigma$. The corresponding mass and width are determined to be $M=2200\pm 6(\mathrm{stat})\pm 5(\mathrm{syst})\mathrm{MeV}/c^2$ and $\mathrm{\Gamma }=104\pm 15(\mathrm{stat})\pm 15(\mathrm{syst})\mathrm{MeV}$, respectively, and the product branching fraction is measured to be $\mathcal{B}(J/\psi \to \eta Y(2175),Y(2175)\to \varphi f_0(980),f_0(980)\to {\pi }^{+}{\pi }^{-})=(1.20\pm 0.14(\mathrm{stat})\pm 0.37(\mathrm{syst}))\times {10}^{-4}$. The results are consistent within errors with those of previous experiments. We also measure the branching fraction of $J/\psi \to \varphi f_1(1285)$ with $f_1(1285)\to \eta {\pi }^{+}{\pi }^{-}$ and set upper limits on the branching fractions for $J/\psi \to \varphi \eta (1405)/\varphi X(1835)/\varphi X(1870)$ with $\eta (1405)/X(1835)/X(1870)\to \eta {\pi }^{+}{\pi }^{-}$ at the 90% confidence level.

The state $Y(2175)$ is observed in the process $e^{+}{e}^{-}\to \eta Y(2175)$ with a statistical significance larger than 10 standard deviations using the data collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies between 3.7 and 4.6 GeV. This is the first observation of the $Y(2175)$ in this process. The mass and width of the $Y(2175)$ are determined to be $(2135\pm 8\pm 9)\mathrm{MeV}/c^2$ and $(104\pm 24\pm 12)\mathrm{MeV}$, respectively, and the production cross section ($\sigma$) of $e^{+}{e}^{-}\to \eta Y(2175)\to \eta \varphi f_0(980)\to \eta \varphi {\pi }^{+}{\pi }^{-}$ is at the several hundred femtobarn level. No significant signal for the process $e^{+}{e}^{-}\to {\eta }^{\prime }Y(2175)$ is observed and the upper limit on $\sigma (e^{+}{e}^{-}\to {\eta }^{\prime }Y(2175))/\sigma (e^{+}{e}^{-}\to \eta Y(2175))$ is estimated to be 0.43 at the 90% confidence level. We also search for $\psi (3686)\to \eta Y(2175)$. No significant signal is observed, indicating a strong suppression relative to the corresponding $J/\psi$ decay, in violation of the “12% rule”.

The decays $J/\psi \to p\overline{p}$ and $J/\psi \to n\overline{n}$ have been investigated with a sample of $225.2\times {10}^6$ $J/\psi$ events collected with the BESIII detector at the BEPCII $e^{+}{e}^{-}$ collider. The branching fractions are determined to be $\mathcal{B}(J/\psi \to p\overline{p})=(2.112\pm 0.004\pm 0.031)\times {10}^{-3}$ and $\mathcal{B}(J/\psi \to n\overline{n})=(2.07\pm 0.01\pm 0.17)\times {10}^{-3}$. Distributions of the angle $\theta$ between the proton or antineutron and the beam direction are well described by the form $1+\alpha {cos}^2\theta$, and we find $\alpha =0.595\pm 0.012\pm 0.015$ for $J/\psi \to p\overline{p}$ and $\alpha =0.50\pm 0.04\pm 0.21$ for $J/\psi \to n\overline{n}$. Our branching-fraction results suggest a large phase angle between the strong and electromagnetic amplitudes describing the $J/\psi \to N\overline{N}$ decay.

We report the first observation of $D^{+}\to {\tau }^{+}{\nu }_{\tau }$ with a significance of $5.1\sigma$. We measure $\mathcal{B}(D^{+}\to {\tau }^{+}{\nu }_{\tau })=(1.20\pm {0.24}_{\text{stat}}\pm {0.12}_{\text{syst}})\times {10}^{-3}$. Taking the world average $\mathcal{B}(D^{+}\to {\mu }^{+}{\nu }_{\mu })=(3.74\pm 0.17)\times {10}^{-4}$, we obtain $R_{\tau /\mu }=\mathrm{\Gamma }(D^{+}\to {\tau }^{+}{\nu }_{\tau })/\mathrm{\Gamma }(D^{+}\to {\mu }^{+}{\nu }_{\mu })=3.21\pm {0.64}_{\text{stat}}\pm {0.43}_{\text{syst}}$., which is consistent with the standard model expectation of lepton flavor universality. Using external inputs, our results give values for the $D^{+}$ decay constant $f_{D^{+}}$ and the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cd}|$ that are consistent with, but less precise than, other determinations.

Using a sample of about 10 billion $J/\psi$ events with the BESIII detector, we search for the weak decays of $J/\psi \to {\overline{D}}^0{\pi }^0+\mathrm{c}.\mathrm{c}.$, $J/\psi \to {\overline{D}}^0\eta +\mathrm{c}.\mathrm{c}.$, $J/\psi \to {\overline{D}}^0{\rho }^0+\mathrm{c}.\mathrm{c}.$, $J/\psi \to D^{-}{\pi }^{+}+\mathrm{c}.\mathrm{c}.$, and $J/\psi \to D^{-}{\rho }^{+}+\mathrm{c}.\mathrm{c}.$. Since no significant signal is observed, we set the upper limits of the branching fractions of these decays to be $\mathcal{B}(J/\psi \to {\overline{D}}^0{\pi }^0+\mathrm{c}.\mathrm{c}.)<4.7\times {10}^{-7}$, $\mathcal{B}(J/\psi \to {\overline{D}}^0\eta +\mathrm{c}.\mathrm{c}.)<6.8\times {10}^{-7}$, $\mathcal{B}(J/\psi \to {\overline{D}}^0{\rho }^0+\mathrm{c}.\mathrm{c}.)<5.2\times {10}^{-7}$, $\mathcal{B}(J/\psi \to D^{-}{\pi }^{+}+\mathrm{c}.\mathrm{c}.)<7.0\times {10}^{-8}$, and $\mathcal{B}(J/\psi \to D^{-}{\rho }^{+}+\mathrm{c}.\mathrm{c}.)<6.0\times {10}^{-7}$ at the 90% confidence level.