Measurement of the branching fraction of and search for a CP -violating asymmetry in η′→π+π−e+e− at BESIII

arXiv: High Energy Physics - Experiment Pub Date : 2020-11-16 DOI:10.1103/PhysRevD.103.092005

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

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引用次数: 2

Abstract

The rare decay $\eta' \to \pi^+ \pi^- e^+ e^-$ is studied using a sample of $1.3 \times 10^9$ $J/\psi$ events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precision to be $\left( 2.42\pm0.05_{stat.}\pm0.08_{syst.} \right) \times 10^{-3}$. In addition, the CP-violating asymmetry in the angle between the decay planes of the $\pi^+\pi^-$-pair and the $e^+e^-$-pair is investigated. A measurable value would indicate physics beyond the standard model; the result is $\mathcal{A}_{CP} = \left(1.6\pm2.0_{stat.}\pm0.6_{syst.} \right)\%$, which is consistent with the standard model expectation of no CP-violation. The precision is comparable to the asymmetry measurement in the $K^0_L\to\pi^+\pi^-e^+e^-$ decay where the observed $(14\pm2)\%$ effect is driven by a standard model mechanism.

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BESIII中η′→π+π−e+e−的分支分数的测量和cp违反不对称性的寻找

利用2009年和2012年在BEPCII的BESIII探测器收集的$1.3 \times 10^9$$J/\psi$事件样本研究了罕见的衰变$\eta' \to \pi^+ \pi^- e^+ e^-$。分支分数测量精度提高为$\left( 2.42\pm0.05_{stat.}\pm0.08_{syst.} \right) \times 10^{-3}$。此外，还研究了$\pi^+\pi^-$ -对和$e^+e^-$ -对衰减面夹角的cp违反不对称性。一个可测量的值将表明超出标准模型的物理;结果为$\mathcal{A}_{CP} = \left(1.6\pm2.0_{stat.}\pm0.6_{syst.} \right)\%$，符合不违反cp的标准模型期望。其精度可与$K^0_L\to\pi^+\pi^-e^+e^-$衰变中的不对称测量相媲美，其中观察到的$(14\pm2)\%$效应是由标准模型机制驱动的。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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arXiv: High Energy Physics - Experiment

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