Test of $C\!P$ Symmetry in Hyperon to Neutron Decays
Creators: name: BESIII Collaboration
name: Ablikim, M.
name: Achasov, M. N.
name: Adlarson, P.
name: Ai, X. C.
name: Aliberti, R.
name: Amoroso, A.
name: An, M. R.
name: An, Q.
name: Bai, Y.
name: Bakina, O.
name: Balossino, I.
name: Ban, Y.
name: Batozskaya, V.
name: Begzsuren, K.
name: Berger, N.
name: Berlowski, M.
name: Bertani, M.
name: Bettoni, D.
name: Bianchi, F.
name: Bianco, E.
name: Bloms, J.
name: Bortone, A.
name: Boyko, I.
name: Briere, R. A.
name: Brueggemann, A.
name: Cai, H.
name: Cai, X.
name: Calcaterra, A.
name: Cao, G. F.
name: Cao, N.
name: Cetin, S. A.
name: Chang, J. F.
name: Chang, T. T.
name: Chang, W. L.
name: Che, G. R.
name: Chelkov, G.
name: Chen, C.
name: Chen, Chao
name: Chen, G.
name: Chen, H. S.
name: Chen, M. L.
name: Chen, S. J.
name: Chen, S. M.
name: Chen, T.
name: Chen, X. R.
name: Chen, X. T.
name: Chen, Y. B.
name: Chen, Y. Q.
name: Chen, Z. J.
name: Cheng, W. S.
name: Choi, S. K.
name: Chu, X.
name: Cibinetto, G.
name: Coen, S. C.
name: Cossio, F.
name: Cui, J. J.
name: Dai, H. L.
name: Dai, J. P.
name: Dbeyssi, A.
name: de Boer, R. E.
name: Dedovich, D.
name: Deng, Z. Y.
name: Denig, A.
name: Denysenko, I.
name: Destefanis, M.
name: De Mori, F.
name: Ding, B.
name: Ding, X. X.
name: Ding, Y.
name: Ding, Y.
name: Dong, J.
name: Dong, L. Y.
name: Dong, M. Y.
name: Dong, X.
name: Du, S. X.
name: Duan, Z. H.
name: Egorov, P.
name: Fan, Y. L.
name: Fang, J.
name: Fang, S. S.
name: Fang, W. X.
name: Fang, Y.
name: Farinelli, R.
name: Fava, L.
name: Feldbauer, F.
name: Felici, G.
name: Feng, C. Q.
name: Feng, J. H.
name: Fischer, K
name: Fritsch, M.
name: Fritzsch, C.
name: Fu, C. D.
name: Fu, J. L.
name: Fu, Y. W.
name: Gao, H.
name: Gao, Y. N.
name: Gao, Yang
name: Garbolino, S.
name: Garzia, I.
name: Ge, P. T.
name: Ge, Z. W.
name: Geng, C.
name: Gersabeck, E. M.
name: Gilman, A
name: Goetzen, K.
name: Gong, L.
name: Gong, W. X.
name: Gradl, W.
name: Gramigna, S.
name: Greco, M.
name: Gu, M. H.
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name: Guan, Z. L.
name: Guo, A. Q.
name: Guo, L. B.
name: Guo, M. J.
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name: Guskov, A.
name: Han, T. T.
name: Han, W. Y.
name: Hao, X. Q.
name: Harris, F. A.
name: He, K. K.
name: He, K. L.
name: Heinsius, F. H. H.
name: Heinz, C. H.
name: Heng, Y. K.
name: Herold, C.
name: Holtmann, T.
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name: Li, Cheng
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name: Zhemchugov, A.
name: Zheng, B.
name: Zheng, J. P.
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name: Zheng, Y. H.
name: Zhong, B.
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name: Zhou, L. P.
name: Zhou, X.
name: Zhou, X. K.
name: Zhou, X. R.
name: Zhou, X. Y.
name: Zhou, Y. Z.
name: Zhu, J.
name: Zhu, K.
name: Zhu, K. J.
name: Zhu, L.
name: Zhu, L. X.
name: Zhu, S. H.
name: Zhu, S. Q.
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Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The quantum entangled $J/ψ\to Σ^{+}\barΣ^{-}$ pairs from $(1.0087\pm0.0044)\times10^{10}$ $J/ψ$ events taken by the BESIII detector are used to study the non-leptonic two-body weak decays $Σ^{+} \to n π^{+}$ and $\barΣ^{-} \to \bar{n} π^{-}$. The $C\!P$-odd weak decay parameters of the decays $Σ^{+} \to n π^{+}$ ($α_{+}$) and $\barΣ^{-} \to \bar{n} π^{-}$ ($\barα_{-}$) are determined to be $-0.0565\pm0.0047_{\rm stat}\pm0.0022_{\rm syst}$ and $0.0481\pm0.0031_{\rm stat}\pm0.0019_{\rm syst}$, respectively. The decay parameter $\barα_{-}$ is measured for the first time, and the accuracy of $α_{+}$ is improved by a factor of four compared to the previous results. The simultaneously determined decay parameters allow the first precision $C\!P$ symmetry test for any hyperon decay with a neutron in the final state with the measurement of $A_{C\!P}=(α_{+}+\barα_{-})/(α_{+}-\barα_{-})=-0.080\pm0.052_{\rm stat}\pm0.028_{\rm syst}$. Assuming $C\!P$ conservation, the average decay parameter is determined as $\left&lt; α_{+}\right&gt;=(α_{+}- \barα_{-})/2 = -0.0506\pm0.0026_{\rm stat}\pm0.0019_{\rm syst}$, while the ratios $α_{+}/α_{0}$ and $\barα_{-}/\barα_{0}$ are $-0.0490\pm0.0032_{\rm stat}\pm0.0021_{\rm syst}$ and $-0.0571\pm0.0053_{\rm stat}\pm0.0032_{\rm syst}$, where $α_{0}$ and $\barα_{0}$ are the decay parameters of the decays $Σ^{+} \to p π^{0}$ and $\barΣ^{-} \to \bar{p} π^{0}$, respectively.