胶子喷注和夸克喷注性质的蒙特卡洛研究

Monte Carlo Study on the Properties of Gluon and Quark Jets

用蒙特卡洛方法研究了 91 2GeVe+e- 碰撞产生的 3喷注事件 .用 3个喷注之间的夹角来标识各个喷注 ,分别计算了 3个喷注的能量及能量分布 ,并在相同能量下计算了 3个喷注的多重数 ,横动量及其分布 .通过与能量相同的 2喷注事件中单夸克喷注的上述性质的比较 ,得到了从 3喷注事件中挑选胶子喷注和夸克喷注的一种简便方法 .这样挑选出来的胶子和夸克喷注在性质上与QCD的理论预言一致 。

The 3 jet events produced in e +e - collisions at 91.2GeV have been studied using Monte Carlo method. After applying two angular cuts the three angles between the jets are used to identify the individual jet in 3 jet events. The energy distributions of the three jets, the mean particle multiplicities, mean transverse momenta of the three jets in equal energy bins and their distributions have been analyzed. Comparing with the corresponding results from the quark jets in 2 jet events, a simple method to select gluon and quark jets from 3 jet events is obtained. The properties of the gluon and quark jets being selected using the introduced method are in qualitative agreement with the expectations of perturbative QCD. The ratio of the mean multiplicity between quark and gluon jets, < N > gluon /< N > quark , has been calculated. The results, again, agree with the experimental results from SLD, OPAL, ALEPH, and DELPHI Collaborations, indicating that the method proposed to select gluon and quark jets from 3 jet events is reasonable.