【作者】 张昆实；

【导师】 刘连寿；

【作者基本信息】 华中师范大学 ， 理论物理， 2002， 硕士

【摘要】 在高能碰撞多粒子产生中，部分子的强子化是一个软过程，不能用微扰QCD来进行研究．所以用唯象分析的方法来研究末态强子系统的性质，以获取关于强相互作用的信息．研究多粒子产生中的喷注内部的动力学起伏，是探索高能碰撞中的动力学机制的一种有效的手段．高能e~+e~-碰撞以其特有的清晰的初态和干净的背景，被认为是研究软-硬过程中的非线性动力学的理想实验．本文对e~+e~-碰撞产生的2-喷注事件中的单喷注子样本和3-喷注事件中的夸克喷注及胶子喷注子样本内部的动力学起伏进行仔细地研究．来探索强相互作用的动力学机制。 本文用阶乘矩分析方法，对质心系能量为91.2GeV的e~+e~-碰撞中产生的2-喷注事件中的单(混合)喷注子样本和在剖分子水平上挑选出的夸克喷注和反夸克喷注子样本分别进行了蒙特卡洛研究．结果表明，喷注内部的动力学起伏的各向异性随着截断参数y_cut的变化面明显地改变．在三种喷注内部都存在着一个显著的转变点．在转变点外，动力学起伏在横平面各向同性，在纵-横平面各向异性。由转变点处的动力学起伏的性质定义了“圆喷注”，得到了产生实验上“可观察喷注”的标度．这些结论与历史上在质心系能量区域17-30Gev第一次在实验中发现第二个喷注(胶子喷注的实验事实是完全一致的。 为了进一步研究3-喷注事件中的夸克(反夸克)喷注和胶子喷注内部的动力学起伏的性质．必须首先解决从3-喷注事件中区分并挑选出夸克，反夸克和胶子喷注来．目前实验上采用所谓的b-tag方法来辨别喷注，虽然这种方法精度较高，但条件要求苛刻，而且统计量小．我们将较直观简单的角度方法加以改进，加入了两个角度限制条件，一个是对3-喷注事件平面性的要求，另一个是为提高对胶子喷注的挑选纯度所加的限制．这样，使得区分挑选出的夸克喷注和胶子喷注的纯度提高到了83％以上．用这种方法研究了3-喷注事件中的正反夸克喷注和胶子喷注的能量，多重数，横动量及其分布等多种一般性质．结果of 自霎霎皇1 了＜L／一1二”人 二卜＼天奏奎／J“人 上 丁J工｝乙人＼－二、－／Hu工ER S 了旺SIS 不仅与＊＊DBffiZ的预言一致，也与多个实验组用卜tag力祛得到的实验 观狈咂一致．从而证明了用改进的角度法则s髓成功地从3－喷注事件中拄睑出 驰，反中克和胶介吹注米· 在以上研究的基础上，本文对用改进的角度脚栩隧出来的夸克账和胶 子哪内部的动力学起伏进行厂Mon比 Carlo研究·结果显示，3－喷注事件中 的夸克喷注和｝喷注事件中的夸克喷注内部有完全相同的动力学起伏性质． 而｝喷注事件中的胶子碰与夸克喷注在A方向上的动力学行为却能不相 同．即：在pt方向上铅喷注内部的动力继伏比胶子喷注内部的狐钢 伏要强．从而揭示了夸克和胶广在强子化碎裂过程中的动力学性质上的区别． 为深索强根互作用的wJ学机制提供了新的线索．更多还原

【Abstract】 As is well known, in high energy collisions the hadromzation of partons, being a soft process, can not be analyzed using perturbative QCD (pQCD). Therefore phcnomcnologieal analysis has to be applied to study the properties of the final state hadronic system, in order to get information which would lead to a better understanding of the dynamics of strong interaction. Investigating the dynamical fluctuations inside jets produced by the fragmentation of partons is an. effective way to explore the dynamics in liigh energy collisions. The experiment of high energy c^e~ collisions, for its simple initial state and clean background, is considered as an idea experiment for the study of the non-linearized dynamics hi soft-hard processes. This thesis studied the dynamical fluctuations inside the single jets in 2-jet events and the quark and gluon jets in 3-jet events carefully to explore the dynamics of strong interaction.The dynamical fluctuations inside the single-jets, the quark jets aad antiquark jets are studied using Monte Carlo method respectively. Quark and antiquark jets are identified from the 2-jet events in e+e~ collisions at 91.2Gev by checking them at parton level. It is found that a transition point exists inside all of these threekinds of jets. At the transition point the dynamical fluctuations are anisotropic in the longitudinal-transverse planes and isotropic in the transverse plane. This means the jets are circular in the transverse plane with respect to the property of dynamical fluctuations at the transition point and therefore they are called the circular jet. The circular jet is consistent with the visible jet which can be observed in experiments. These results are in agreement with the fact that the third jet (gluon jet) was historically first discovered in e+e- collisions in the energy region 17-30Gev.In order to study the dynamical fluctuations inside the gluon jets and quark jets, the improved angular rule is proposed to identify these tv/o kinds of jets from the 3-jet events. Two angular cuts are applied to increase the purity of selection of gluon jets and quark jets up to more than 83%. The general properties ( the mean energy, mean multiplicity, mean transvese momentum etc. and their distribution) inside the gluon and quark jets, being studied using the improved angular rule, are in agreement with the expectations of QCD as well as the results from experiments using the b-tag method proving the improved angular rule proposed to identify the gluon and quark jets from the 3-jet events is reasonable.Based on the above analysis, the dynamical fluctuations inside the gluon jets and (mark jets are investigated separately using Monte Carlo method. The results show that the properties of dynamical fluctuations inside the quark jets in the 3-jct events is the same as that in the 2-jet events. While in the 3-jet events the dynamical fluctuations in pt direction inside quark jets is stronger than that inside gluon jets indicating the fragmentation dynamics in these two kinds of jets is quite different. New clue thus provided for the exploring of dynamics of strong interaction.更多还原