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Register a new userObservation of $eta_{c}$ decay into $Sigma^{+}bar{Sigma}^{-}$ and $Xi^{-}bar{Xi}^{+}$ final states
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Using a data sample of $2.25times10^{8}$ $J/psi$ events collected with the BESIII detector, we present the first observation of the decays of $eta_{c}$ mesons to $Sigma^{+}bar{Sigma}^{-}$ and $Xi^{-}bar{Xi}^{+}$. The branching fractions are measured to be $(2.11pm0.28_{rm stat.}pm0.18_{rm syst.}pm0.50_{rm PDG})times10^{-3}$ and $(0.89pm0.16_{rm stat.}pm0.08_{rm syst.}pm0.21_{rm PDG})times10^{-3}$ for $eta_{c} to Sigma^{+}bar{Sigma}^{-}$ and $Xi^{-}bar{Xi}^{+}$, respectively. These branching fractions provide important information on the helicity selection rule in charmonium-decay processes.
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The Xi^0 muon semi-leptonic decay has been observed for the first time with nine identified events using the KTeV beam line and detector at Fermilab. The decay is normalized to the Xi^0 beta decay mode and yields a value for the ratio of decay rates of $(1.8^{+0.7}_{-0.5}(stat.)pm0.2(syst.))times 10^{-2}$. This is in agreement with the SU(3) flavor symmetric quark model.
Using $(448.1pm2.9)times 10^{6}$ $psi(3686)$ events collected with the BESIII detector and a single-baryon tagging technique, we present the first observation of the decays $psi(3686)toXi(1530)^{0}bar{Xi}(1530)^{0}$ and $Xi(1530)^{0}bar{Xi}^0$. The branching fractions are measured to be ${cal{B}}(psi(3686)toXi(1530)^{0}bar{Xi}(1530)^{0}) = (6.77pm0.14pm0.39)times10^{-5}$ and ${cal{B}}(psi(3686)toXi(1530)^{0}bar{Xi}^{0}) = (0.53pm0.04pm0.03)times10^{-5}$. Here, the first and second uncertainties are statistical and systematic, respectively. In addition, the parameter associated with the angular distribution for the decay $psi(3686)toXi(1530)^{0}bar{Xi}(1530)^0$ is determined to be $alpha = 0.32pm0.19pm0.07$, in agreement with theoretical predictions within one standard deviation.
From the 2002 data taking with a neutral kaon beam extracted from the CERN-SPS, the NA48/1 experiment observed 97 $Xi^{0}rightarrow Sigma^{+} mu^{-} bar{ u}_{mu}$ candidates with a background contamination of $30.8 pm 4.2$ events. From this sample, the BR($Xi^{0}rightarrow Sigma^{+} mu^{-} bar{ u}_{mu}$) is measured to be $(2.17 pm 0.32_{mathrm{stat}}pm 0.17_{mathrm{syst}})times10^{-6}$.
Using $(10.087pm0.044)times10^{9}$ $J/psi$ events collected by the BESIII detector at the BEPCII collider, we search for the hyperon semileptonic decay $Xi^{-} rightarrow Xi^{0} e^{-} bar{ u}_{e}$. No significant signal is observed and the upper limit on the branching fraction $mathcal B(Xi^{-} rightarrow Xi^{0} e^{-} bar{ u}_{e})$ is set to be $2.59times10^{-4}$ at 90 % confidence level. This result is one order of magnitude more strict than the previous best limit.
We study the decays of the charmonium resonances $J/psi$ and $psi(3686)$ to the final states $Xi^{-}barXi^{+}$, $Sigma(1385)^{mp}barSigma(1385)^{pm}$ based on a single baryon tag method using data samples of $(223.7 pm 1.4) times 10^{6}$ $J/psi$ and $(106.4 pm 0.9) times 10^{6}$ $psi(3686)$ events collected with the BESIII detector at the BEPCII collider. The decay $psi(3686)rightarrowSigma(1385)^{mp}barSigma(1385)^{pm}$ is observed for the first time, and the measurements of the other processes, including the branching fractions and angular distributions, are in good agreement with and much more precise than the previously published results. Additionally, the ratios $frac{{cal{B}}(psi(3686)rightarrowXi^{-}barXi^{+})}{{cal{B}}(J/psirightarrowXi^{-}barXi^{+})}$, $frac{{cal{B}}(psi(3686)rightarrowSigma(1385)^{-}barSigma(1385)^{+})}{{cal{B}}(J/psirightarrowSigma(1385)^{-}barSigma(1385)^{+})}$ and $frac{{cal{B}}(psi(3686)rightarrowSigma(1385)^{+}barSigma(1385)^{-})}{{cal{B}}(J/psirightarrowSigma(1385)^{+}barSigma(1385)^{-})}$ are determined.
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