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تسجيل مستخدم جديدStudy of $J/psi$ and $psi(3686)$ decay to $Lambdabar{Lambda}$ and $Sigma^0bar{Sigma}^0$ final states
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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.
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From $1310.6times10^{6}$ $J/psi$ and $448.1times10^{6}$ $psi(3686)$ events collected with the BESIII experiment, we report the first observation of $Sigma^{+}$ and $bar{Sigma}^{-}$ spin polarization in $e^+e^-rightarrow J/psi (psi(3686)) rightarrow S
igma^{+} bar{Sigma}^{-}$ decays. The relative phases of the form factors $DeltaPhi$ have been measured to be $(-15.5pm0.7pm0.5)^{circ}$ and $(21.7pm4.0pm0.8)^{circ}$ with $J/psi$ and $psi(3686)$ data, respectively. The non-zero value of $DeltaPhi$ allows for a direct and simultaneous measurement of the decay asymmetry parameters of $Sigma^{+}rightarrow p pi^{0}~(alpha_0 = -0.998pm0.037pm0.009)$ and $bar{Sigma}^{-}rightarrow bar{p} pi^{0}~(bar{alpha}_0 = 0.990pm0.037pm0.011)$, the latter value being determined for the first time. The average decay asymmetry, $(alpha_{0} - bar{alpha}_{0})/2$, is calculated to be $-0.994pm0.004pm0.002$. The CP asymmetry $A_{rm CP,Sigma} = (alpha_0 + bar{alpha}_0)/(alpha_0 - bar{alpha}_0) = -0.004pm0.037pm0.010$ is extracted for the first time, and is found to be consistent with CP conservation.
Using $1310.6times10^{6}$ $J/psi$ and $448.1times10^{6}$ $psi(3686)$ events collected with the BESIII detector, the branching fractions of $J/psi$ and $psi(3686)$ decays to $Sigma^{+}overline{Sigma}^{-}$ are measured to be $(10.61 pm 0.04 pm 0.36) ti
mes 10^{-4}$ and $(2.52 pm 0.04 pm 0.09) times 10^{-4}$, respectively. In addition, the ratio of $mathcal{B}(psi(3686) rightarrow Sigma^{+}overline{Sigma}^{-})/mathcal{B}(J/psi rightarrow Sigma^{+}overline{Sigma}^{-})$ is determined to be $(23.8 pm 1.1)%$ which violates the $12%$ rule.
Based on $4.481times10^8$ $psi(3686)$ events collected with the BESIII detector at BEPCII, the branching fraction of the isospin violating decay $psi(3686)rightarrowbar{Sigma}^{0}Lambda+c.c.$ is measured to be $(1.60 pm 0.31 pm 0.13~pm~0.58) times 10
^{-6}$, where the first uncertainty is statistical, the second is systematic, and the third is the uncertainty arising from interference with the continuum. This result is significantly smaller than the measurement based on CLEO-c data sets. The decays $chi_{cJ} rightarrowLambdabar{Lambda}$ are measured via $psi(3686)rightarrowgammachi_{cJ}$, and the branching fractions are determined to be $mathcal{B}left(chi_{c0}rightarrowLambdabar{Lambda}right)=(3.64 pm 0.10 pm 0.10 pm 0.07)times 10^{-4}$, $mathcal{B}left(chi_{c1}rightarrowLambdabar{Lambda}right)=(1.31pm0.06 pm 0.06 pm0.03)times 10^{-4}$, $mathcal{B}left(chi_{c2}rightarrowLambdabar{Lambda}right)=(1.91pm0.08 pm 0.17 pm0.04)times 10^{-4}$, where the third uncertainties are systematic due to the $psi(3686) rightarrow gamma chi_{c J}$ branching fractions.
BESIII data show a particular angular distribution for the decay of the $J/psi$ and $psi(2S)$ mesons into the hyperons $Lambdaoverline{Lambda}$ and $Sigma^0overline{Sigma}^0$. More in details the angular distribution of the decay $psi(2S) to Sigma^0o
verline{Sigma}^0$ exhibits an opposite trend with respect to that of the other three channels: $J/psi to Lambdaoverline{Lambda}$, $J/psi to Sigma^0overline{Sigma}^0$ and $psi(2S) to Lambdaoverline{Lambda}$. We define a model to explain the origin of this phenomenon.
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