Coherent contribution to the Z 0 hadronic width following flavor-coherent formation of u, d quarks

Abstract

The hadronic decay of Z 0 proceeds, in part, through the flavor-coherent formation of uū and dd̄ quark-antiquark pairs. The subsequent hadronization is a coherent process which respects the G-parity invariance of strong interactions. As a consequence, there are flavor-coherent contributions to the hadronic width which are not included in the incoherent quark model for decays. We show here, by explicit computation of some low-multiplicity channels in a model with small constituent quarks, that the coherent ΔΓ c can be of the order of an MeV. It therefore can effect the determination of α s from the gluonic correction to the hadronic width in the incoherent quark model formula. Direct measurement of the probability for two charged prongs in the hadronic multiplicity distribution is of importance in determining the role of compact constituent quarks in coherent amplitudes for hadronization.