Instanton-induced semihard parton interactions and phenomenology of high energy hadron collisions

Abstract

We study phenomenologically whether partonic collisions responsible for the growth of hadron-hadron cross sections at high energy can be ascribed to instanton-induced processes. Although nonperturbative in nature, these interactions occur at the semihard scale $Q\ensuremath{\sim}1--2 \mathrm{GeV},$ and should therefore be described using information from deep inelastic leptonic scattering on the partonic constituents in nucleons, pions, and photons. After considering shadowing corrections in nucleon-nucleon scattering, we fix a free instanton tail suppression parameter and determine the effective quark-quark cross section. The resulting contributions to $NN,$ $\ensuremath{\pi}N,$ $\ensuremath{\gamma}N,$ and $\ensuremath{\gamma}\ensuremath{\gamma}$ cross sections all increase with energy differently, but in reasonable agreement with experimental data. We then proceed to an estimate of the number of such processes present in high energy Au-Au collisions at BNL RHIC, finding that the amount of entropy produced by instanton or sphaleron events matches the observed amount.