Anomalous pion production induced by nontrivial topological structure of QCD vacuum

TL;DR

This paper proposes a novel mechanism for pion production in high energy reactions, induced by instantons in the QCD vacuum, which dominates in certain energy regions and may explain large spin effects.

Contribution

It introduces a new instanton-induced pion production mechanism that does not rely on fragmentation functions, providing a dominant contribution in specific energy and momentum ranges.

Findings

Instanton mechanism dominates pion production at a few GeV transverse momentum.

The mechanism explains large spin asymmetries in high energy reactions.

Calculations show significant contribution to inclusive $$-meson production.

Abstract

A new mechanism for the pion production in the high energy reactions is suggested. It is related to the possibility for direct production of the pions induced by instantons, topologically nontrivial gluonic excitations of QCD vacuum. This mechanism does not require any fragmentation functions for production of pseudoscalar mesons in high energy reactions with hadrons. We calculate the contribution of a new mechanism to the inclusive $\pi^0$-meson production in high energy proton-proton collision. It is shown that it gives the dominated contribution to the inclusive cross-sections in the few GeV region for the transverse momentum of final pion. We discuss the possible application of a new mechanism to the phenomenon of the large spin effects observed in the numerous high energy reactions.