Effect of jet production on the multiplicity dependence of average transverse momentum

The geometrical branching model for multiparticle production is used to study the multiplicity dependence of the average transverse momentum 〈$p_T$ ${〉}_n$ of charged particles produced in the central region of pp¯ collisions. The production of jets is shown to be responsible for the increase of 〈$p_T$ ${〉}_n$ with multiplicity. We demonstrate that beyond the plateau region that follows the initial steep rise the jets cause 〈$p_T$ ${〉}_n$ to have a further increase at even higher multiplicities. The physical basis of this ‘‘ledge’’ effect is discussed and contrasted from an earlier speculation based on phase transition.