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Register a new userFirst observation of the isospin violating decay $J/psirightarrow Lambdabar{Sigma}^{0}+c.c.$
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Using a sample of $(225.2pm 2.8)times 10^6$ $J/psi$ events collected with the BESIII detector, we present results of a study of $J/psirightarrow gammaLambdabar{Lambda}$ and report the first observation of the isospin violating decay $J/psirightarrowLambdabar{Sigma}^{0}+c.c.$, in which $bar{Sigma}^{0}$ decays to $gamma bar{Lambda}$. The measured branching fractions are $mathcal{B}(J/psirightarrowbar{Lambda}Sigma^{0}$) = $(1.46pm0.11pm0.12) times10^{-5}$ and $mathcal{B}(J/psirightarrowLambdabar{Sigma^{0}}$) = $(1.37pm0.12pm0.11) times10^{-5}$. We search for $Lambda(1520) rightarrow gamma Lambda$ decay, and find no evident signal, and an upper limit for the product branching fraction $mathcal{B}(J/psirightarrowLambdabar{Lambda}(1520)+c.c.)times mathcal{B}(Lambda(1520)rightarrowgammaLambda)<4.1 times10^{-6}$ is set at the 90% confidence level. We also report the observation of $eta_{c}rightarrowLambdabar{Lambda}$ in $J/psi rightarrow gamma eta_{c}$, $eta_{c}rightarrowLambdabar{Lambda}$ and measure the branching fraction $mathcal{B}(eta_{c}rightarrowLambdabar{Lambda}) =(1.16pm0.12 (stat)pm0.19(syst)pm0.28(PDG))times10^{-3}$.
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Using E1 radiative transitions $psi(3686) to gammachi_{cJ}$ from a sample of $(448.1 pm 2.9)times10^{6}$ $psi(3686)$ events collected with the BESIII detector, the decays $chi_{cJ}to Sigma^{+}bar{p}K_{S}^{0}+c.c.~(J = 0, 1, 2)$ are studied. The decay branching fractions are measured to be $mathcal{B}(chi_{c0}to Sigma^{+}bar{p}K_{S}^{0}+c.c.) = (3.52 pm 0.19pm 0.21)times10^{-4}$, $mathcal{B}(chi_{c1}to Sigma^{+}bar{p}K_{S}^{0}+c.c.) = (1.53 pm 0.10pm 0.08)times10^{-4}$, and $mathcal{B}(chi_{c2}to Sigma^{+}bar{p}K_{S}^{0}+c.c.) = (8.25 pm 0.83 pm 0.49)times10^{-5}$, where the first and second uncertainties are the statistical and systematic ones, respectively. No evident intermediate resonances are observed in the studied processes.
Using a sample of 1.31 billion $J/psi$ events collected with the BESIII detector at the BEPCII collider, the decays $J/psi to phi pi^{+}pi^{-}pi^{0}$ and $J/psi to phi pi^{0}pi^{0}pi^{0}$ are investigated. The isospin violating decay $J/psi to phi pi^{0} f_{0}(980)$ with $f_{0}(980) to pipi$, is observed for the first time. The width of the $f_{0}(980)$ obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the $pi^{0} f_{0}(980)$ mass spectrum, there is evidence of $f_1(1285)$ production. By studying the decay $J/psi to phieta$, the branching fractions of $eta to pi^{+}pi^{-}pi^{0}$ and $eta to pi^{0}pi^{0}pi^{0}$, as well as their ratio, are also measured.
Using $1310.6times10^6$ $J/psi$ and $447.9times10^6$ $psi(3686)$ events collected with the BESIII detector at the BEPCII $e^{+}e^{-}$ collider, the branching fractions and the angular distributions of $J/psi$ and $psi(3686)$ decays to $Lambdabar{Lambda}$ and $Sigma^0bar{Sigma}^0$ final states are measured. The branching fractions are in agreement with, and much more precise than, the averages of previously published results. The polar angular distributions of $psi(3686)$ decays are measured for the first time, while those of $J/psi$ decays are measured with much improved precision. In addition, the ratios of branching fractions $frac{mathcal{B}(psi(3686)toLambdabar{Lambda})}{mathcal{B}(J/psitoLambdabar{Lambda})}$ and $frac{mathcal{B}(psi(3686)toSigma^0bar{Sigma}^0)}{mathcal{B}(J/psitoSigma^0bar{Sigma}^0)}$ are determined to test the 12% rule.
Using data samples collected at center of mass energies of $sqrt{s}$ = 4.009, 4.226, 4.257, 4.358, 4.416 and 4.599 GeV with the BESIII detector operating at the BEPCII storage ring, we search for the isospin violating decay $Y(4260)rightarrow J/psi eta pi^{0}$. No signal is observed, and upper limits on the cross section $sigma(e^{+}e^{-}rightarrow J/psi eta pi^{0})$ at the 90% confidence level are determined to be 3.6, 1.7, 2.4, 1.4, 0.9 and 1.9 pb, respectively.
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