Longitudinal Coherence in a Holographic Model of p-Pb Collisions

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 nd that all constituents act coherently, and their separation leaves no imprint on the resulting plasma, when this separation is . 0:26=Thyd, with Thyd the temperature of the plasma at the time when hydrodynamics rst 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.