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,
{"title":"Measurement of the branching fraction of and search for a \nCP\n-violating asymmetry in \nη′→π+π−e+e−\n at BESIII","authors":"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,","doi":"10.1103/PhysRevD.103.092005","DOIUrl":null,"url":null,"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.","PeriodicalId":8429,"journal":{"name":"arXiv: High Energy Physics - Experiment","volume":"108 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"2","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv: High Energy Physics - Experiment","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1103/PhysRevD.103.092005","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
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.