QCD COHERENT BRANCHING AND SEMIINCLUSIVE PROCESSES AT LARGE X

Using the QCD coherent branching algorithm, we compute the Deep Inelastic Scattering and Drell-Yan hard cross sections in the semi-inclusive region of large x. The calculation is done to next-to-leading logarithmic accuracy in the resummation of perturbative QCD. We compare the results with the known analytical expressions to the same accuracy in the MSBAR subtraction scheme. They coincide if one defines an improved branching algorithm suitable for Monte Carlo simulation, in which the two-loop running coupling constant and Altarelli-Parisi splitting function are used. Therefore such a simulation can be used to measure LAMBDA-MSBAR from these semi-inclusive cross sections. Moreover we show that the same results can also be obtained using the usual one-loop splitting function, provided the scale parameter LAMBDA-MC used in the Monte Carlo simulation is related to LAMBDA-MSBAR by a computed factor: LAMBDA-MC = 1.569 LAMBDA-MSBAR (for five flavours).