夸克喷注和胶子喷注硬度特性的研究  

Study of the Hardness Property of Quark and Gluon Jets

作　　者：陈刚[1] 刘连寿[2] 

机构地区：[1]中国地质大学物理系,武汉430074 [2]华中师范大学粒子物理研究所,武汉430079

出　　处：《高能物理与核物理》2004年第5期469-474,共6页High Energy Physics and Nuclear Physics

基　　金：湖北省教育厅重点科研项目;湖北省高校优秀中青年科技创新项目和国家自然科学基金 ( 10 3 4715 2;10 3 75 0 2 5 ;90 10 3 0 19)资助~~

摘　　要：用蒙特卡洛模拟方法研究了Z0 强子衰变中的三喷注事件 .用b标记方法辨别 ,得到夸克喷注和胶子喷注 .定义了一个新的物理量———硬度 .分别计算了发射了胶子的夸克喷注和胶子喷注的硬度分布 .通过胶子和夸克喷注的平均多重数和平均横动量对硬度的依赖性以及他们的多重数和横动量在相同硬度区间内的分布情况的计算与比较 ,发现夸克喷注和胶子喷注的硬度特性有显著的差别 .夸克喷注的特性几乎与硬度无关 ,而胶子喷注的特性与硬度之间存在较强的关联 .当Hd>10GeV时 ,胶子喷注的平均多重数和平均横动量都明显地大于夸克喷注的平均多重数和平均横动量 ;而当Hd <6GeV时 ,结果正好相反 .这表明 ,只是对于较硬的胶子 ,胶子喷注比夸克喷注“胖”的结论才能成立 .The 3-jet events from hadronic Z0 decay is studied using Monte-Carlo simulation. Quark and Gluon jets are identified through the b-tag method. A new physical quantity——hardness is defined, and the hardness distributions of quark and gluon jets are calculated. The dependence of the average multiplicity and average transverse momentum on hardness as well as the multiplicity and transverse momentum distributions in a certain hardness range in the quark and gluon jets are calculated respectively, and compared. It is found that the properties of quark and gluon jets are considerably different in these respects. The properties of quark jets are almost independent on hardness, while those of gluon jets have strong correlation with hardness. When H-d>10GeV the average multiplicity and average tranverse momentum of gluon jets are higher than those of quark jets; but when H-d<6GeV the results are reversed. This indicates that the conclusion on gluon jets being “fatter” than quark jets is valid only for hard gluons.

关 键 词：高能物理学 胶子喷注 夸克喷注 硬度 b标记 蒙特卡洛模拟 量子色动力学 

分 类 号：O572.3[理学—粒子物理与原子核物理]