Mini-jet Total Cross-sections and Overlap Functions through Bloch-Nordsieck Summation

Predictions for total inelastic cross-sections for photon induced processes are discussed in the context of the QCD-inspired minijet model. Large theoretical uncertainties exist, some of them related to the parton distributions of hadrons in impact parameter space. A model for such distribution is presented, based on soft gluon summation. This model incorporates (the salient features of distributions obtained from) the intrinsic transverse momentum behaviour of hadrons. Under the assumption that the intrinsic behaviour is dominated by soft gluon emission stimulated by the scattering process, the b-spectrum becomes softer and softer as the scattering energy increases. In minijet models for the inclusive cross-sections, this will counter the increase from σjet . The impact of parton scattering on the rise of inclusive cross-sections with energy was suggested by Cline and Halzen [1], after such rise was first observed in proton-proton collisions at ISR . Minijet models were put forward to describe quantitatively the further rise at higher energy [2, 3, 4] and eikonal minijet models [5, 6, 7, 8] were subsequently developed to include an increasing number of partonic collisions in QCD resulting from the rapid rise in gluon densities. Recent measurements of photoand hadro-production Presented by G. Pancheri at Hadron Structure ’96, Stara Lesna, Feb. 12-17, 1996 On leave of absence from Dept. of Physics, Uni. of Bombay, Bombay, India