Initial state azimuthal anisotropies in small collision systems

Abstract

Strong multiparticle azimuthal correlations have recently been observed in high energy proton-nucleus collisions. While final state collective effects can be responsible for many of the observed effects, the domain structure in the classical color field of a high energy nucleus, naturally also leads to such multiparticle correlations. We describe recent calculations of the momentum space 2-particle cumulant azimuthal anisotropy coefficients νn{2}, n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. We find significant differences between Wilson lines from the MV model and from JIMWLK evolution. We also discuss the relation of this calculation to earlier work on the ridge correlation obtained in the “glasma graph” approximation, and to the “color electric field domain model.”