B-]S- A QCD-CONSISTENT ANALYSIS OF THE PHOTON ENERGY-DISTRIBUTION(GAMMA )

The photon energy distribution in the inclusive b --> s + gamma transi tions is a combination of two components: the first component, soft ph ysics, is determined by the so-called primordial distribution function , while the second component, perturbative physics, is governed by har d gluon emission. A simple ansatz is suggested for the primordial dist ribution function which obeys the QCD constraints known so far. We the n discuss in detail how hard gluon emission affects the energy distrib ution. An extension of the Sudakov approximation is worked out incorpo rating the Brodsky-Lepage-Mackenzie prescription and its generalizatio ns. We explicitly calculate the marriage of nonperturbative and pertur bative effects in the way required by OPE, introducing separation scal e mu. A few parameters, such as m(b) and mu(pi)(2) affect the shape of the distribution and, thus, can be determined by matching to the expe rimental data. The data, still scarce, while not giving precise values for these parameters, yield consistency with theory: the current valu es of the above parameters lie within experimental uncertainty. On the theoretical side we outline a method allowing one to go beyond the pr actical version of OPE.