Tests of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>C</mml:mi><mml:mi>P</mml:mi></mml:math> symmetry in entangled <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi mathvariant="normal">Ξ</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mo>−</mml:mo><mml:msup><mml:mover accent="true"><mml:mi mathvariant="normal">Ξ</mml:mi><mml:mo stretchy="false">¯</mml:mo></mml:mover><mml:mn>0</mml:mn></mml:msup></mml:math> pairs
M. Ablikim, М. Н. Ачасов, P. Adlarson, X. Ai, R. Aliberti, A. Amoroso, M. R. An, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann, H. Cai, X. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Çetin, J. F. Chang, T. T. Chang, W. L. Chang, G. R., G. Chelkov, C. Chen, Chao Chen, G. Chen, Haifeng Chen, M. L. Chen, S. J. Chen, S. M. Chen, T. Chen, Xiaoyan Chen, X. T. Chen, Y. B. Chen, Y. Q. Chen, Z. J. Chen, W. S. Cheng, S. K. Choi, X. Chu, G. Cibinetto, S. C. Coen, F. Cossio, J. J. Cui, H. L. Dai, J. P. Dai, A. Dbeyssi, R. E. de Boer, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, B. Ding, X. X. Ding, Y. Ding, Y. Ding, J. Dong, L. Y. Dong, M. Y. Dong, X. Dong, M. C. Du, S. X. Du, Z. H. Duan, P. Egorov, Y. L. Fan, J. Fang, S. S. Fang, Wenxing Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, K. Fischer, M. Fritsch, C. Fritzsch, C. D. Fu, J. Fu, Y. W. Fu, He Gao, Yang Gao, Yang Gao, S. Garbolino, I. Garzia, P. T. Ge
Abstract
The J/ψ → Ξ0Ξ ̄ 0 process and subsequent decays are investigated using (10087 pm 44) x10^6 J/ψ events collected at the BESIII experiment. The decay parameters of Ξ0 and Ξ ̄ 0 are simultaneously measured to be α = −0.3750 pm 0.0034 pm 0016, α ̄ Ξ = 0.3790 pm 0.0034 pm 0.0021, φΞ = 0.0051 pm 0.0096 pm 0.0018 rad, φ ̄ Ξ = −0.0053 pm 0.0097 pm 0.0019 rad with unprecedented accuracies, where the first and the second uncertainties are statistical and systematic, respectively. The most precise values for CP asymmetry observables of Ξ0 decay are obtained to be AΞCP = (−5.4 pm 6.5 pm 3.1) x 10^-3 and DeltaPhi_CP = (−0.1 pm 6.9 pm 0.9) 10^-3 rad. For the first time, the weak and strong phase differences are determined to be ξP − ξS = (0.0 pm 1.7 pm 0.2)x10^-2 rad, which are the most precise results for any weakly decaying baryon. These results will play important roles in the studies of the CP violations and polarizations for the strange, charmed, and beauty baryons.