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arXiv · 2004.07701

$\Sigma^{+}$ and $\bar{\Sigma}^-$ polarization in the $J/\psi$ and $\psi(3686)$ decays

BESIII Collaboration·M. Ablikim·M. N. Achasov·P. Adlarson·S. Ahmed·M. Albrecht·A. Amoroso·Q. An·Anita·Y. Bai·O. Bakina·R. Baldini Ferroli·I. Balossino·Y. Ban·K. Begzsuren·J. V. Bennett·N. Berger·M. Bertani·D. Bettoni·F. Bianchi·J Biernat·J. Bloms·A. Bortone·I. Boyko·R. A. Briere·H. Cai·X. Cai·A. Calcaterra·G. F. Cao·N. Cao·S. A. Cetin·J. F. Chang·W. L. Chang·G. Chelkov·D. Y. Chen·G. Chen·H. S. Chen·M. L. Chen·S. J. Chen·X. R. Chen·Y. B. Chen·W. Cheng·G. Cibinetto·F. Cossio·X. F. Cui·H. L. Dai·J. P. Dai·X. C. Dai·A. Dbeyssi·R. B. de Boer·D. Dedovich·Z. Y. Deng·A. Denig·I. Denysenko·M. Destefanis·F. De Mori·Y. Ding·C. Dong·J. Dong·L. Y. Dong·M. Y. Dong·S. X. Du·J. Fang·S. S. Fang·Y. Fang·R. Farinelli·L. Fava·F. Feldbauer·G. Felici·C. Q. Feng·M. Fritsch·C. D. Fu·Y. Fu·X. L. Gao·Y. Gao·Y. G. Gao·I. Garzia·E. M. Gersabeck·A. Gilman·K. Goetzen·L. Gong·W. X. Gong·W. Gradl·M. Greco·L. M. Gu·M. H. Gu·S. Gu·Y. T. Gu·C. Y Guan·A. Q. Guo·L. B. Guo·R. P. Guo·Y. P. Guo·A. Guskov·S. Han·T. T. Han·T. Z. Han·X. Q. Hao·F. A. Harris·K. L. He
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Abstract

From $1310.6\times10^{6}$ $J/\psi$ and $448.1\times10^{6}$ $\psi(3686)$ 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 $\Delta\Phi$ have been measured to be $(-15.5\pm0.7\pm0.5)^{\circ}$ and $(21.7\pm4.0\pm0.8)^{\circ}$ with $J/\psi$ and $\psi(3686)$ data, respectively. The non-zero value of $\Delta\Phi$ allows for a direct and simultaneous measurement of the decay asymmetry parameters of $\Sigma^{+}\rightarrow p \pi^{0}~(\alpha_0 = -0.998\pm0.037\pm0.009)$ and $\bar{\Sigma}^{-}\rightarrow \bar{p} \pi^{0}~(\bar{\alpha}_0 = 0.990\pm0.037\pm0.011)$, the latter value being determined for the first time. The average decay asymmetry, $(\alpha_{0} - \bar{\alpha}_{0})/2$, is calculated to be $-0.994\pm0.004\pm0.002$. The CP asymmetry $A_{\rm CP,\Sigma} = (\alpha_0 + \bar{\alpha}_0)/(\alpha_0 - \bar{\alpha}_0) = -0.004\pm0.037\pm0.010$ is extracted for the first time, and is found to be consistent with CP conservation.

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BESIII Collaboration, M. Ablikim, M. N. Achasov, P. Adlarson, S. Ahmed, M. Albrecht, A. Amoroso, Q. An, Anita, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, K. Begzsuren, J. V. Bennett, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, J Biernat, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Cetin, J. F. Chang, W. L. Chang, G. Chelkov, D. Y. Chen, G. Chen, H. S. Chen, M. L. Chen, S. J. Chen, X. R. Chen, Y. B. Chen, W. Cheng, G. Cibinetto, F. Cossio, X. F. Cui, H. L. Dai, J. P. Dai, X. C. Dai, A. Dbeyssi, R. B. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, Y. Ding, C. Dong, J. Dong, L. Y. Dong, M. Y. Dong, S. X. Du, J. Fang, S. S. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, M. Fritsch, C. D. Fu, Y. Fu, X. L. Gao, Y. Gao, Y. G. Gao, I. Garzia, E. M. Gersabeck, A. Gilman, K. Goetzen, L. Gong, W. X. Gong, W. Gradl, M. Greco, L. M. Gu, M. H. Gu, S. Gu, Y. T. Gu, C. Y Guan, A. Q. Guo, L. B. Guo, R. P. Guo, Y. P. Guo, A. Guskov, S. Han, T. T. Han, T. Z. Han, X. Q. Hao, F. A. Harris, K. L. He. 2020-04-16. $\Sigma^{+}$ and $\bar{\Sigma}^-$ polarization in the $J/\psi$ and $\psi(3686)$ decays. https://doi.org/10.1103/physrevlett.125.052004

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