Instanton-induced Semi-hard Parton Interactions and Phenomenology of High Energy Hadron Collisions

We phenomenologically study whether partonic collisions responsible for the growth of hadron-hadron cross sections at high energy can be ascribed to instanton-induced processes. Although non-perturbative in nature, these interactions occur at the semi-hard scale $Q\sim 1-2$ 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 $NN$, $\pi N$, $\gamma N$, and $\gamma\gamma$ 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 RHIC, finding that the amount of entropy produced by instanton/sphaleron events matches the observed amount.