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Register a new userObservation of the Decay Xi^0 --> Sigma^+ mu^- nu(bar)
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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.
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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 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.
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.
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.
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.
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