Initial state angular asymmetries in high energy p+A collisions: spontaneous breaking of rotational symmetry by a color electric field and C-odd fluctuations

TL;DR

This paper introduces a model explaining initial azimuthal asymmetries in high-energy p+A collisions through spontaneous rotational symmetry breaking caused by color electric fields and C-odd fluctuations, linking microscopic QCD effects to observable anisotropies.

Contribution

It presents a novel model connecting initial-state anisotropies to spontaneous symmetry breaking in the color field, incorporating both C-even and C-odd effects in a unified framework.

Findings

Parity even harmonics from the real part of the dipole S-matrix

Parity odd harmonics from the C-odd odderon contribution

Qualitative estimates of C-odd fluctuation amplitudes and cutoffs

Abstract

We present a simple model for generating initial-state azimuthal asymmetries in pA collisions from dipole scattering on an anisotropic dense target. Parity even angular harmonics arise from the C-even real part of the dipole S-matrix which spontaneously breaks rotational symmetry in two dimensions due to a condensate for the color electric field. This leads to an angular correlation with the direction of $\vec E$. Parity odd harmonics are generated by the C-odd imaginary part (odderon) due to coupling to coherent target fluctuations which again break rotational invariance. We perform a first qualitative extraction of the amplitude and cutoff of C-odd fluctuations in the dense target.