Λ_(c)^(+)→Λh^(+)和Λc+→∑^(0)h^(+)(h=K,π)衰变道CP破坏的寻找和其分支比与衰变不对称参数的测量  

Search for CP violation and measurement of branching fractions and decay asymmetry parameters for Λ_(c)^(+)→Λh^(+)and Λ_(c)^(+)→Σ^(0)h^(+)(h=K,π)

作　　者：Belle合作组 L.K.Li The Belle Collaboration

机构地区：[1]不详

出　　处：《Science Bulletin》2023年第6期583-592,M0004,共11页科学通报（英文版）

基　　金：supported by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan;the Japan Society for the Promotion of Science (JSPS);the Tau-Lepton Physics Research Center of Nagoya University;the Australian Research Council including grants DP180102629, DP170102389, DP170102204, DE220100462, DP150103061, FT130100303;Austrian Federal Ministry of Education, Science and Research (FWF) and FWF Austrian Science Fund No. P 31361-N36;the National Natural Science Foundation of China under Contracts No. 11675166, No. 11705209;No. 11805064;No. 11975076;No. 12135005;No. 12175041;No. 12161141008;Key Research Program of Frontier Sciences, Chinese Academy of Sciencess (CAS), Grant No. QYZDJ-SSW-SLH011;the Shanghai Science and Technology Committee (STCSM) under Grant No. 19ZR1403000;the Ministry of Education, Youth and Sports of the Czech Republic under Contract No. LTT17020;the Czech Science Foundation Grant No. 22-18469S;Horizon 2020 ERC Advanced Grant No. 884719 and ERC Starting Grant No. 947006 ‘‘Inter Leptons” (European Union);the Carl Zeiss Foundation, the Deutsche Forschungsgemeinschaft, the Excellence Cluster Universe, and the Volkswagen Stiftung;the Department of Atomic Energy (Project Identification No. RTI 4002);the Department of Science and Technology of India;the Istituto Nazionale di Fisica Nucleare of Italy;National Research Foundation (NRF) of Korea Grant Nos. 2016R1D1A1B02012900, 2018R1A2B3003643, 2018R1A6A1A060 24970, RS202200197659, 2019R1I1A3A01058933, 2021R1A6A1A03043957, 2021R1F1A1060423, 2021R1F1A1064008, 2022R1A2C 1003993;Radiation Science Research Institute, Foreign Large-size Research Facility Application Supporting project;the Global Science Experimental Data Hub Center of the Korea Institute of Science and Technology Information and KREONET/GLORIAD;the Polish Ministry of Science and Higher Education and the National Science Center;the Ministry of Science and Higher Education of the Russian Federation, Agreement 14.W03.31.0026;the HSE University Basic Research Program, Moscow;

摘　　要：本文报告了粲重子Λ_(c)^(+)的四个弱衰变道Λ_(c)^(+)→Λh^(+)和Λ_(c)^(+)→∑^(0)h^(+)(h=K,π)的系列研究.基于在KEKB能量不对称的正负电子对撞机上的Belle探测器收集的980 fb-1数据样本,作者测量了粲重子两体单卡比玻压低(SCS)衰变过程中的直接电荷共轭-宇称(CP)不对称:ACPdir(Λ_(c)^(+)→ΛK^(+))=+0.021±0.026±0.001和ACPdir(Λ_(c)^(+)→∑^(0)K^(+))=+0.025±0.054±0.004;精确测量了衰变不对称参数(α)和其引起的CP不对称度:AC^(α)_(P)(Λ_(c)^(+)→ΛK^(+))=-0.023±0.086±0.071和AC^(α)_(P)(Λ_(c)^(+)→∑^(0)K^(+))=+0.08±0.035±0.14.这是粲重子SCS衰变的第一个AC^(α)_(P)结果;其次,作者在实验上利用粲重子衰变来寻找超子CP破坏,即利用Λ_(c)^(+)→(Λ,∑^(0))π^(+)衰变获得AC^(α)_(P)(Λ→pπ-)=+0.013±0.007±0.011.以上测量均未发现重子CP破坏的证据.此外,该文还报告了Λ_(c)^(+)两个SCS衰变道的分支比测量:B(Λ_(c)^(+)-ΛK^(+))=(6.57±0.17±0.11±0.35)×10^(-4)和B(Λ_(c)^(+)→∑^(0)K^(+))=(3.58±0.19±0.06±0.19)×10^(-4),这些均为目前最精确的结果.We report a study of Λ_(c)^(+)→Λh^(+)and Λ_(c)^(+)→∑^(0)h^(+)(h=K,π)decays based on a data sample of 980 fb-1 collected with the Belle detector at the KEKB energy-asymmetric e+e-collider.Thefirst results of direct CP asymmetry in two-body singly Cabibbo-suppressed(SCS)decays of charmed baryons are measured,Ad ir CP Λ_(c)^(+)→KK^(+)=+0.021±0.026±0.001 and Ad ir CP Λ_(c)^(+)→∑^(0)K^(+)=+0.025±0.054±0.004.We also make the most precise measurement of the decay asymmetry parameters(a)for the four modes of interest and search for CP violation via the a-induced CP asymmetry(AC^(α)_(P)).We measure AC^(α)_(P) Λ_(c)^(+)→KK^(+)=-0.023±0.086±0.071 and AC^(α)_(P) Λ_(c)^(+)→∑^(0)K^(+)=+0.08±0.35±0.14,which are thefirst AC^(α)_(P) results for SCS decays of charmed baryons.We search for K-hyperon CP violation in Λ_(c)^(+)→K,∑^(0)π^(+)andfind AC^(α)_(P)(K→pπ-)=+0.013±0.007±0.011.This is thefirst time that hyperon CP violation has been mea-sured via Cabibbo-favored charm decays.No evidence of baryon CP violation is found.We also obtain the most precise branching fractions for two SCS Λ_(c)^(+)decays,B Λ_(c)^(+)→KK^(+)=(6.57±0.17±0.11±0.35)×10^(-4)and B Λ_(c)^(+)→∑^(0)K^(+)=(3.58±0.19±0.06±0.19)×10^(-4).Thefirst uncertainties are statistical and the second systematic,while the third uncertainties come from the uncertainties on the world average branching frac-tions of Λ_(c)^(+)→K,∑^(0)π^(+).

关 键 词：CP violation Charmed baryon Singly Cabibbo-suppressed decay Branching fraction Decay asymmetry parameter CP asymmetry 

分 类 号：O571.3[理学—粒子物理与原子核物理]