Finite-energy results of the parton model for the e+e− annihilation

Abstract

A parton model for the e+e− annihilation which is valid at finite energies is constructed by taking into account the energy conservation and the effect of the finite transverse momentum relative to the jet axis. We study the production of the pseudoscalar nonet and of the baryon octet. By imposing constraints such as the Drell-Yan-West relation, the phase-space behaviour at smallx and the inclusive sum rules for energy and multiplicity, we are able to construct a simple model for the fragmentation function. Below the possible threshold of new particles, our model reproduces data on single-particle distributions and the charged-energy fraction.SU 3 symmetry relations for the fragmentation functions are satisfied after mass-breaking effect is taken into account. We throw light on various aspects of the e+e− annihilation in the course of approaching the scaling limit by studying the energy dependence of single-particle distributions, particle ratios, average charged and photon multiplicities and charged-energy fraction. Our model is supposed to describe the light-quark (u, d and s) component of the hadronic cross-section. We can learn about the nature of the new particles by comparing data above the new-particle threshold with our prediction (the difference between the two should be attributed to new degrees of freedom). In particular, we have estimated the average charged multiplicity and the charged-energy fraction of the charmed-quark component.