Using a data sample corresponding to an integrated luminosity of 2.93 fb\(^{-1}\) collected at a center-of-mass energy of 3.773~GeV with the BESIII detector at the BEPCII collider, we search for a ...scalar partner of the \(X(3872)\), denoted as \(X(3700)\), via \(\psi(3770)\to \gamma\eta\eta'\) and \(\gamma\pi^{+}\pi^{-}J/\psi\) processes. No significant signals are observed and the upper limits of the product branching fractions \( {\cal B}(\psi(3770)\to\gamma X(3700))\cdot {\cal B}(X(3700)\to \eta\eta')\) and \({\cal B}(\psi(3770)\to\gamma X(3700))\cdot {\cal B}(X(3700)\to\pi^{+}\pi^{-}J/\psi)\) are determined at the 90\% confidence level, for the narrow \(X(3700)\) with a mass ranging from 3710 to 3740 MeV/\(c^2\), which are from 0.8 to 1.8 \((\times 10^{-5})\) and 0.9 to 3.4 \((\times 10^{-5})\), respectively.
We perform a study of the \(X(3872)\) lineshape using the data samples of \(e^+e^-\to\gamma X(3872)\), \(X(3872)\to D^0\bar{D}^0 \pi^0\) and \(\pi^+\pi^- J/\psi\) collected with the BESIII detector. ...The effects of the coupled-channels and the off-shell \(D^{*0}\) are included in the parameterization of the lineshape. The lineshape mass parameter is obtained to be \(M_{X}=(3871.63\pm 0.13^{+0.06}_{-0.05})\) MeV. Two poles are found on the first and second Riemann sheets corresponding to the \(D^{*0}\bar{D}^0\) branch cut. The pole location on the first sheet is much closer to the \(D^{*0}\bar{D}^0\) threshold than the other, and is determined to be \(7.04\pm0.15^{+0.07}_{-0.08}\) MeV above the \(D^0\bar{D}^0\pi^0\) threshold with an imaginary part \(-0.19\pm0.08^{+0.14}_{-0.19}\) MeV.
By analyzing \((448.1\pm2.9)\times10^6\) \(\psi(3686)\) events collected with the BESIII detector operating at the BEPCII collider, the decays of \(\chi_{cJ} \to \Lambda\bar \Lambda \eta\) (\(J=0\), ...1 and 2) are observed for the first time with statistical significances of \(13.9\sigma\), \(6.7\sigma\), and \(8.2\sigma\), respectively. The product branching fractions of \(\psi(3686)\to\gamma\chi_{cJ}\) and \(\chi_{cJ}\to \Lambda\bar \Lambda \eta\) are measured. Dividing by the world averages of the branching fractions of \(\psi(3686)\to\gamma\chi_{cJ}\), the branching fractions of \(\chi_{cJ}\to \Lambda\bar \Lambda \eta\) decays are determined to be \((2.31\pm0.30\pm0.21)\times10^{-4}\), \((5.86\pm1.38\pm0.68)\times10^{-5}\), and \((1.05\pm0.21\pm0.15)\times10^{-4}\) for \(J=0\), 1 and 2, respectively, where the first uncertainties are statistical and the second systematic.
Using \(e^+e^-\) annihilation data corresponding to an integrated luminosity of 2.93 fb\(^{-1}\) taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first ...measurements of the branching fractions of the inclusive decays \(D^0\to \pi^+\pi^+\pi^-X\) and \(D^+\to \pi^+\pi^+\pi^-X\), where pions from \(K^0_S\) decays have been excluded from the \(\pi^+\pi^+\pi^-\) system and \(X\) denotes any possible particle combination. The branching fractions of \(D^0(D^+)\to \pi^+\pi^+\pi^-X\) are determined to be \({\mathcal B}(D^0\to \pi^+\pi^+\pi^-X)=(17.60\pm0.11\pm0.22)\%\) and \({\mathcal B}(D^+\to \pi^+\pi^+\pi^-X)=(15.25\pm0.09\pm0.18)\%\), where the first uncertainties are statistical and the second systematic.
We report the first search for \(\bar\Lambda\)--\(\Lambda\) oscillations in the decay \(J/\psi \to p K^- \bar{\Lambda} + c.c.\) by analyzing \(1.31\times10^9\) \(J/\psi\) events accumulated with the ...BESIII detector at the BEPCII collider. The \(J/\psi\) events are produced using \(e^+e^-\) collisions at a center of mass energy \(\sqrt{s}= 3.097\)~GeV. No evidence for hyperon oscillations is observed. The upper limit for the oscillation rate of \(\bar\Lambda\) to \(\Lambda\) hyperons is determined to be \(\mathcal{P}(\Lambda)=\frac{\mathcal{B}(J/\psi\to pK^-\Lambda+c.c.)}{\mathcal{B}(J/\psi\to pK^-\bar\Lambda+c.c.)}<4.4\times10^{-6}\) corresponding to an oscillation parameter \(\delta m_{\Lambda\bar\Lambda}\) of less than \(3.8\times10^{-18}\)~GeV at the 90\% confidence level.
Based on 4.5 fb\(^{-1}\) data taken at seven center-of-mass energies ranging from 4.600 to 4.699 GeV with the BESIII detector at the BEPCII collider, we measure the branching fractions of ...\(\Lambda_{c}^{+}\rightarrow\Sigma^{+}+hadrons\) relative to \(\Lambda_{c}^{+}\rightarrow \Sigma^+ \pi^+ \pi^-\). Combining with the world average branching fraction of \(\Lambda_{c}^{+}\rightarrow \Sigma^+ \pi^+ \pi^-\), their branching fractions are measured to be \((0.377\pm0.042\pm0.018\pm0.021)\%\) for \(\Lambda_{c}^{+}\rightarrow\Sigma^{+} K^{+} K^{-}\), \((0.200\pm0.023\pm0.010\pm0.011)\%\) for \(\Lambda_{c}^{+}\rightarrow\Sigma^{+} K^{+} \pi^{-}\), \((0.414\pm0.080\pm0.029\pm0.023)\%\) for \(\Lambda_{c}^{+}\rightarrow\Sigma^{+}\phi\) and \((0.197\pm0.036\pm0.008\pm0.011)\%\) for \(\Lambda_{c}^{+}\rightarrow\Sigma^{+}K^{+} K^{-}\)(non-\(\phi\)). In all the above results, the first uncertainties are statistical, the second are systematic and the third are from external input of the branching fraction of \(\Lambda_{c}^{+}\rightarrow \Sigma^+ \pi^+ \pi^-\). Since no signal for \(\Lambda_{c}^{+}\rightarrow\Sigma^{+} K^{+} \pi^{-}\pi^{0}\) is observed, the upper limit of its branching fraction is determined to be 0.11\% at the 90\(\%\) confidence level.
Using data corresponding to an integrated luminosity of \(651~\mathrm{pb}^{-1}\) accumulated at 22 center-of-mass energies from 2.00 to 3.08 GeV by the BESIII experiment, the process ...\(e^{+}e^{-}\to\phi\pi^{+}\pi^{-}\) is studied. The cross sections for \(e^{+}e^{-}\to\phi\pi^{+}\pi^{-}\) are consistent with previous results, but with improved precision. To measure the mass and width of the structure observed in the cross section line shape, a combine fit is performed after enhancing the contribution from \(\phi f_{0}(980)\). The fit reveals a structure with the mass of \(M=2178\pm20\pm5~{\rm MeV}/c^2\) and the width of \(\varGamma=140\pm36\pm16~{\rm MeV}\), where the first uncertainties are statistical and the second ones are systematic.
The \(J/\psi \to \Xi^0 \bar{\Xi}^{0}\) process and subsequent decays are investigated using \((10087 \pm 44)\times 10^6\) \(J/\psi\) events collected at the BESIII experiment. The decay parameters of ...\(\Xi^0\) and \(\bar{\Xi}^0\) are measured with greatly improved precision over previous measurements to be \(\alpha_{\Xi} = -0.3750 \pm 0.0034 \pm 0.0016\), \(\bar{\alpha}_{\Xi} = 0.3790 \pm 0.0034 \pm 0.0021\), \(\phi_{\Xi} = 0.0051 \pm 0.0096 \pm 0.0018\)~rad, \(\bar{\phi}_{\Xi} = -0.0053 \pm 0.0097 \pm 0.0019\)~rad, where the first and the second uncertainties are statistical and systematic, respectively. From these measurements, precise \(CP\) symmetry tests in \(\Xi^0\) decay are performed, and \(A^{\Xi}_{CP} = (-5.4 \pm 6.5 \pm 3.1) \times 10^{-3}\) and \(\Delta\phi^{\Xi}_{CP} = (-0.1 \pm 6.9 \pm 0.9) \times 10^{-3}\)~rad are consistent with \(CP\) conservation. The sequential decay also enables a separation of weak and strong phase differences, which are found for the first time to be \(\xi_{P}-\xi_{S} = (0.0 \pm 1.7 \pm 0.2) \times 10^{-2}\)~rad and \(\delta_{P}-\delta_{S} = (-1.3 \pm 1.7 \pm 0.4)\times 10^{-2}\)~rad, respectively. In addition, we measure the \(\Lambda\) decay parameters and test \(CP\) symmetry in \(\Lambda\) decays.
Using \((1.0087\pm0.0044)\times10^{10}\) \(J/\psi\) events collected by the BESIII detector at the BEPCII collider, we search for the lepton number violation decay \(\phi \to \pi^+ \pi^+ e^- e^-\) ...via \(J/\psi\to \phi\eta\). No signal is found and the upper limit on the branching fraction of \(\phi \to \pi^+ \pi^+ e^- e^-\) is set to be \(9.7\times10^{-6}\) at the 90\% confidence level.
The Born cross sections and effective form factors of the process \(e^+e^-\to\Lambda\bar\Sigma^0 + c.c.\) are measured at 14 center-of-mass energy points from 2.3094 to 3.0800 GeV, based on data ...corresponding to an integrated luminosity of \((478.5 \pm 4.8)\ \text{pb}^{-1}\) collected with the BESIII detector. A non-zero Born cross section is observed at the center-of-mass energy of 2.3094 GeV with a statistical significance of more than five standard deviations, and the cross sections at other energies are obtained with improved precision compared to earlier measurements from the BaBar Collaboration. The Born cross-section lineshape is described better by a shape with a plateau near the threshold than by a pQCD motivated functional form.
