Longitudinal Coherence in a Holographic Model of p-Pb Collisions

TL;DR

This study uses holographic simulations of shock wave collisions to show that constituent coherence in p-Pb collisions results in a unified plasma behavior, with no imprint of initial separation when below a certain scale.

Contribution

It demonstrates that constituents in holographic shock wave models act coherently, influencing the initial conditions and evolution of the resulting plasma in heavy ion collisions.

Findings

Constituents act coherently when separation is less than ~0.26/T_{hyd}.

Center-of-mass of plasma matches that of all constituents, not individual collisions.

No imprint of constituent separation on plasma when below coherence scale.

Abstract

As a model of the longitudinal structure in heavy ion collisions, we simulate gravitational shock wave collisions in anti-de Sitter space in which each shock is composed of multiple constituents. We find that all constituents act coherently, and their separation leaves no imprint on the resulting plasma, when this separation is $\lesssim 0.26 / T_{hyd}$, with $T_{hyd}$ the temperature of the plasma at the time when hydrodynamics first becomes applicable. In particular, the center-of-mass of the plasma coincides with the center-of-mass of all the constituents participating in the collision, as opposed to the center-of-mass of the individual collisions. We discuss the implications for nucleus-nucleus and proton-nucleus collisions.