τ- Charm Energy Region Produce Examples Of Sub-optimization Model Of Hadrons

It is known that perturbative quantum chromodynamics (QCD) works well at high energy region due to the asymptotic behavior. The BESIII experiment focus on studies of x-charm physics, where perturbative QCD lose power to predict the light hadron production, and small momentum transfer soft processes. Phenomenologically, a lot of models are proposed to describe the light hadron production. In this energy region, measurement on the charged hadron multiplicity distribution, momentum distribution and event shapes for hadron decays will help to determine parameters, which are introduced in the phenomenological models.With this motivation, the thesis present results on the optimization of parameters for Lundcharm and PYTHIA model. They are:1. Using J/ψ decays collected with BESⅢ detector at April2012, light hadron decays are selected, and event shapes and the charged hadron multiplicity distribution are studied. The dependence of the response function on model parameters is approximated up to the quadratic term, and model parameters are optimized by simultaneously fitting J/ψ inclusive charged track distributions and event shapes. The Monte-Carlo (MC) simulations show that optimal parameters yield satisfactory MC distributions as compared to both of the J/ψ and ψ(2S) data distributions. These optimal values are suggested for the Lundcharm model to produce J/ψ and ψ(2S) decays to light hadrons.2. Using the data taken at the center-of-mass energy3.65GeV, parameters to control the light hadron production in PYTHIA model are optimized with the same method. These optimal values are suggested as standard ones for generation of light hadrons in continuum processes in ι-charm energy region.