Low projectile density contributions in the dilute-dense CGC framework for two-particle correlations

Abstract

At leading-order, the standard dilute-dense Color Glass Condensate formula used for two-particle correlations in proton-nucleus collisions, whose symmetries prevent the generation of odd azimuthal anisotropy harmonics, is the dilute projectile limit of the dense-dense formalism. However, when the projectile is genuinely dilute, the complete formulation contains additional contributions at the same leading order in the strong coupling constant. In this work we investigate those low projectile density contributions that are relevant when the particles are produced at forward rapidities. We find that they are responsible for non-zero odd harmonics which are negative, in qualitative agreement with recent experimental measurements at the Relativistic Heavy-Ion Collider.

Particle Production in pA Collisions at Mid-Rapidity in the Color Glass Condensate

“…First of all, it is straightforward to realize that the spectrum is symmetric under (k 1 , k 2 ) → (k 1 , −k 2 ), which is known as the "accidental symmetry of the CGC". The effects of this symmetry have been widely discussed in the context of the particle correlations in the literature, and it is argued that it can be broken by (i) adopting a nonlinear Gaussian approximation for the double-dipole operator [60], including density corrections to the dilute projectile [61][62][63] or (ii) including the subeikonal corrections [64][65][66][67] in the computation of the double-inclusive gluon spectrum.…”