A Study On The Dynamical Fluctuations Inside Jets In E～+e～- Collisions

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.