Ultracentral Collisions of Small and Deformed Systems at RHIC: ${U} {U}$, ${d} {Au}$, ${}^{9}{Be} {Au}$, ${}^{9}{Be} {}^{9}{Be}$, ${}^{3}{He} {}^{3}{He}$, and ${}^{3}{He} {Au}$ Collisions

Understand

In this paper, we study a range of collision systems involving deformed ions and compare the elliptic and triangular flow harmonics produced in a hydrodynamics scenario versus a color glass condensate (CGC) scenario.

• For the hydrodynamics scenario, we generate initial conditions using TRENTO and work within a linear response approximation to obtain the final flow harmonics.
• For the CGC scenario, we use the explicit calculation of two-gluon correlations taken in the high-$p_T$ ``(semi)dilute-(semi)dilute'' regime to express the flow harmonics in terms of the density profile of the collision.
• We consider ultracentral collisions of deformed ions as a testbed for these comparisons because the difference between tip-on-tip and side-on-side collisions modifies the multiplicity dependence in both scenarios, even at zero impact parameter.