The Cwz Subtraction Scheme (a New Renormalization Prescription for Qcd) and its Application.

When we consider low energy phenomena in the light of the fact that several heavy quarks exist, the 't Hooft minimal subtraction (MS) scheme is deficient in the fact that it gives terms with large logarithms of the mass in renormalized quantities. The CWZ (Collins-Wilczek-Zee) scheme is a method to alleviate this problem. The renormalization factors (Z(,1), Z(,2) and Z(,3)) and coefficients of the renormalization group equation, as well as the QCD parameter (LAMDA), are calculated in CWZ scheme in this thesis. The applications of CWZ scheme to perturbative QCD calculations (such as the running coupling, the Sudakov factor and the evolution of moments of parton distributions) are presented. A detailed computation of DIS (Deep Inelastic Scattering) in both MS and CWZ schemes is also carried out. A "C factor" is defined for linking the two schemes. Numerical computations have shown that the CWZ scheme can be used reliably.