【作者】 郭玉萍；

【导师】 喻纯旭；

【作者基本信息】 南开大学 ， 粒子物理与原子核物理， 2013， 博士

【摘要】 北京谱仪(BES)Ⅲ是工作在北京正负电子对撞机(BEPC)Ⅱ上的大型通用磁谱仪。从2008年第一次对撞成功到2011年底,BESⅢ采集了225兆J/Ψ、106兆Ψ′、480pb-1质心能量(√s)为4.009GeV的Ψ(4040)正负电子对撞事例、827pb-1质心能量为4.260GeV对撞事例、545pb-1质心能量为4.360GeV对撞事例以及质心能量在4.260GeV和4.360GeV附近的扫描数据。利用这批数据,本文对粲偶素的部分辐射跃迁和强子跃迁进行了实验研究,包括精确测量粲偶素基态粒子-ηc的共振参数、对P波粲偶素χcJ强子跃迁过程χcJ→ηcπ+π-的实验寻找、首次在4.260GeV和4.360GeV观测到强子跃迁过程e+e-→π+π-hc并首次观测到带电类粲偶素Zc(4020),具体描述为：·对ψ’→γKKπππ过程(包括KS0K±π+π+π-和K+K-π+π-π0)进行了分析。-通过ψ→γηc,ηc→KKπππ过程测量了ηc的共振参数。在描述KKπππ不变质量谱时,使用考虑了Ψ′→γηc过程和低质量赝标介子相同末态过程的干涉的概率密度函数(PDF),成功描述了ηc的共振曲线。联合另外4个强子衰变末态,ηc的质量测量为mηc=2984.3±0.6±0.6MeV/c2,宽度测量为Γηc=32.0±1.2±1.0MeV,两项误差中第一项表示统计误差,第二项表示系统误差。这是目前世界上20多个测量中精度最高的单个测量,首次将ηc共振参数的测量误差降低到1MeV水平。-通过ψ’→γχcJ,χcJ→ηcππ+-,ηc→KS0K±π+和ηc→K+K-π0过程对χcJ(J=0,1,2)的强子跃迁过程χcJ→ηcπ+π-进行了实验寻找。在3个χcJ质量区间内ηc的两个衰变末态中均没有观测到明显的信号,基于现有数据首次给出了90%置信度下χc0→ηcπ+π-和χc1→ηcπ+π-衰变分支比的上限,确定了χc2→ηcπ+π-衰变分支比更严格的上限。χcJ强子跃迁衰变分支比上限测量为：B(χc0→ηcπ+π-→(KS0K±π+)π+π-)<0.07%, B(χco→ηcπ+π-→(K+K-π0)π+π-)<0.41%,B(χc1→ηcπ+π-→(KS0K±π+)π+π-)<0.32%, B(χc1→ηcπ+π-→(KS0K±π+)π+π-)<0.44%, B(χc2→ηcπ+π-→(KS0K±π+)π+π-)<0.54%, B(χc2→ηcπ+π-→(K+K-π0)π+π-)<1.23%,与理论计算相比,χc1→ηccπ+π-衰变分支比的上限比理论计算值低约一个量级。一首次测量了χc1→KS0K±π+π+π-、χc1→K+K-π+π+π-π0、χcJ→ωK+K-和χc1→φπ+π-π0(J=0,1,2)过程的衰变分支比,其中χcJ由电偶极跃迁过程ψ’→γχcJ衰变得到。χcJ强子衰变末态分支比测量为：B(χc0→KS0K±π+π+π-)=(4.22±0.10±0.43)×10-3, B(χc0→K+K-π+π+π0)=(8.61±0.13±0.94)×10-3, B(χc0→ωK+K-)=(1.94±0.06±0.20)×10-3, B(χc0→φπ+π-π0)=(1.18±O.07±0.13)×10-3, B(χc1→KS0K±π+π+π-)=(7.52±0.11±0.79)×10-3, B(χc1→K+K-π+π+π0)=(11.46±0.12±1.29)×10-3, B(χc1→ωK+K-)=(0.78±0.04±0.08)×10-3, B(χc1→φπ+π-π0)=(0.75±0.06±0.08)×10-3, B(χc2→KS0K±π+π+π-)=(7.30±0.11±0.75)×10-3, B(χc2→K+K-π+π+π0)=(11.69±0.13±1.31)×10-3, B(χc2→ωK+K-)=(0.73±0.04±0.08)×10-3, B(χc2→φπ+π-π0)=(0.93±0.06±0.10)×10-3.·对强子跃迁过程e+e-→π+π-hc进行了实验寻找,h_c由电偶极跃迁过程hc→γηc进行重建,η_c用16个强子衰变末态重建,用墨标记叼。的强子衰变末态Xi={pp,π+π-pp,2(π+π-),2(K+K-),π+π-K+K-,3(π+π-),K+K-2(π+π-),KS0±π+,KS0K±π+π+π-,K+K-π0，ppπ0, π+π-η, K+K-η,2(π+π-)η,π+π-π0π0,2(π+π-π0)]。在质心能量、／j=4.260GeV和质心能量咖=4.360GeV数据中首次观测到e+e-π+π-hc反应过程,其玻恩截面分别测量为(41.0士2.8±3.6士6.4)pb和(52.3±3.7±4.1士8.2)pb。同时在这两个能量点的数据中,π±h_c不变质量谱上观测到一个带电的类粲偶素-Zc(4020),其质量和宽度分别测量为M=(4021.8±1.0±2.5)MeV/c2和r=(5.7士3.4士1.1)MeV,统计显著度为6.40"。其衰变性质决定其至少含有四个夸克,极有可能是一个奇特态强子。e+e-→Zc(4020)±π+→π+π-hc的衰变几率与e+e→π+π-hc的衰变几率的比值在4.260GeV和4.360GeV数据中分别为和在Ψ(4040)数据中,16个衰变末态中均没有观测到明显的信号,基于16个衰变末态γXi不变质量谱之和,在90%置信度下确定了质心能量=4.009GeV处e+e-→π+π-hc观测截面的上限为σ(e+e-→π+π-hc)<1.5pb；相当于B(ψ(4040)→π+π-hc)<0.26×10-3。更多还原

【Abstract】 Radiative transitions of ψ’ and hadronic transitions of XcJ are studied with the106M ψ’ events data sample, the hadronic process of e+e→π+π-hc are studied with827pb-1e+e-collision data at (?)=4.260GeV,545pb-1e+e-collision data at (?)=4.360GeV, and480pb-1ψ(4040) events data sample at (?)=4.009GeV; hadronic production of e+e-→π+π-hc is observed with data at4.260GeV and4.360GeV with an observation of a charged charmoniumlike state, the Zc(4020). All these data used were accumulated with the Beijing Spectrometer (BES) Ⅲ at the Beijing Electron Position Collider (BEPC) Ⅱ. The thesis includes the following two parts:?ψ’→γKKπππ(KKπππ represents KS0K±π+π+π-and K+K-π+π-π0), in-cluding the possible intermediate states are studied.-Precision measurement of the properties of ηc via ψ’→γηc, ηc→KKπππ. Using the model that incorporates interference between the signal reaction, ψ’→γηc, and a non-resonant radiative background to describe the line shape of the ηc, the mass and width of ηc are determined to be2984.3±0.6±0.6MeV/c2and32.0±1.2±1.0MeV, respectively, the first errors are statistical and the second ones are systematic. The results are the most precise measurement so far.-Search for the hadronic transition XcJ→ηcπ+π-via ηc→KS0K±π+and ηc→K+K-π0.No obvious ηc signals are observed in any of the three χcJ states in either ηc decay mode. At90%confidence level, the upper limits of B(χcJ→ηcπ+π-)are determined,which are: B(χc0→ηcπ+π-→(KS0±π+)π+π-)<0.07%, B(χc0→ηcπ+π-→(K+K-π0)π+π-)<0.41%, B(χc1→ηcπ+π-→(KS0±K±π+)π+π-)<0.32%, B(χc1→ηcπ+π-→(K+K-π0)π+π-)<0.44%, B(χc2→ηcπ+π-→(KS0K±π+)π+π-)<0.54%, B(χc2→ηcπ+π-→(K+K-π0)π+π-)<1.23%, The upper limit of BB(χc1→ηcπ+π-)is lower than the existing theoretical prediction by almost an order of magnitude.一Observation of B(χC1→KKπππ,here the χcJ originates from the E1transi-tion ψ→χcJ.The branching fractions of χcJ→KS0K±π+π+π-,χcJ→K+K-π+π-π0,χcJ→ωK+K-,and χcJ→φπ+π-π0are measured for the first time,which are: B(χc0→KS0K±π+π+π-)=(4.22±0.10±0.43)×10-3, B(χc0→K+K-π+π+π-)=(8.61±0.13±0.94)×10-3, B(χc0→ωK+K-)=(1.94±0.06±0.20)×10-3, B(χc0→φπ+π-π0)=(1.18±0.07±0.13)×10-3, B(χc1→KS0K±π+π+π-)=(7.52±0.11±0.79)×10-3, B(χc1→K+K-π+π+π-)=(11.46±0.12±1.29)×10-3, B(χc1→ωK+K-)=(0.78±0.04±0.08)×10-3, B(χc1→φπ+π-π0)=(0.75±0.06±0.08)×10-3, B(χc2→KS0K±π+π+π-)=(7.30±0.11±0.75)×10-3, B(χc2→K+K-π+π+π-)=(11.69±0.13±1.31)×10-3, B(χc2→ωK+K-)=(0.73±0.04±0.08)×10-3, B(χc2→φπ+π-π0)=(0.93±0.06±0.10)×10-3.Study of e+e-→π+π-hc via hc→γηc,ηc→Xi,here Xi={pp,π+π-pp,2(π+π-),2(K+K-),π+π-K+K-,3(π+π-),K+K-2(π+π-),KS0K±π+, KS0K±π+π+π-, K+K-π0, ppπ0,π+π-η, K+K-η,2(π+π-)η,π+π--π0π0,2(π+π-π0)}.The process e+e-→π+π-hc is first observed at4.260GeV and4.360GeV,the Born cross sections are measured to be(41.0±2.8±3.6±6.4)pb and(52.3±3.7±4.1±8.2)pb,respectively.In the process e+e-→π+π-hc at (?)=4.260GeV and4.360GeV,a charged chamoniumlike structure Zc(4020) in the mass spectrum of π±hc with a statistical significance of6.4σ is observed. Its mass and width are measured to be M=(4021.8±1.0±2.5)MeV/c2and r=(5.7±3.4±1.1)MeV,respectively.And its production ratio is measured to be and The Zc(4020)can be in- terpreted as an exotic hadron with at least four quarks.No obvious signals are observed in the summed invariant mass spectrum of γXi(16ηc decay modes) at ψ(4040),the upper limit of the cross section of e+e-→π+π-hc at(?)=4.009GeV is determined to be σ(e+e-→π+π-hc)<1.5pb at90%confidence level,corresponds to B(ψ(4040)→π+π-hc)<0.26×10-3.更多还原