Assessing saturation physics explanations of collectivity in small collision systems with the IP-Jazma model

Understand

Experimental measurements in collisions of small systems from p+p to p/d/3He+A at RHIC and the LHC reveal particle emission patterns that are strikingly similar to those observed in A+A collisions.

• One explanation of these patterns is the formation of small droplets of quark-gluon plasma followed by hydrodynamic evolution.
• A geometry engineering program was proposed [1] to investigate these emission patterns, and the experimental data from that program in p+Au, d+Au, 3He+Au collisions for elliptic and triangular anisotropy coefficients v2 and v3 follow the pattern predicted by hydrodynamic calculations [2].
• One alternative approach, referred to as initial-state correlations, suggests that for small systems the patterns observed in the final-state hadrons are encoded at the earliest moments of the collision, and therefore require no final-state parton scattering or hydrodynamic evolution [3,4].