Quark splitting in non-trivial \theta-vacuum

TL;DR

This paper investigates how a non-trivial topological heta-vacuum in QCD modifies quark splitting functions, leading to potential helicity imbalance in quark jets, with implications for heavy-ion collision phenomenology.

Contribution

It introduces a modified quark propagator in pQCD to analyze the effects of topological QCD backgrounds on quark splitting functions, revealing degeneracy and potential helicity imbalance.

Findings

Quark splitting functions are altered by topological backgrounds.

Degeneracy of splitting functions for left- and right-handed quarks.

Possible helicity imbalance in quark jets in heavy-ion collisions.

Abstract

Quark splitting in non-trivial $\theta$-vacuum with a given helicity is investigated in pQCD with a modified quark propagator. We found that the quark splitting functions were modified by the presence of a topologically non-trivial QCD background field, though there is no explicit helicity flip associated with the radiative processes. The interaction with the topological non-trivial field leads to the degeneracy of the quark splitting functions for left- and right-handed quarks. Such degeneracy can lead to imbalance of left- and right-handed quarks in quark jet showers. We also discuss phenomenological consequences of such imbalance if there exists non-trivial topological gluon field configuration in heavy-ion collisions.