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Register a new userA model to explain angular distributions of $J/psi$ and $psi(2S)$ decays into $Lambdaoverline{Lambda}$ and $Sigma^0overline{Sigma}^0$
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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 $psi(2S) to Sigma^0overline{Sigma}^0$ 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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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.
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 $e^+e^-rightarrow J/psi (psi(3686)) rightarrow Sigma^{+} bar{Sigma}^{-}$ 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 $(10.61 pm 0.04 pm 0.36) times 10^{-4}$ 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.
A search for the rare decays of $J/psi to D_s^-rho^+ + c.c.$ and $J/psi to overline{D}{}^0overline{K}{}^{ast0} + c.c.$ is performed with a data sample of 225.3 million $J/psi$ events collected with the BESIII detector. No evident signal is observed. Upper limits on the branching fractions are determined to be $mathcal{B}(J/psi to D_s^-rho^+ + c.c.) < 1.3 times 10^{-5}$ and $mathcal{B}(J/psi to overline{D}{}^0overline{K}{}^{ast0} + c.c.) < 2.5 times 10^{-6}$ at the $90%$ confidence level.
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