Anisotropic fluctuations of momentum and angular momentum of heavy quarks in the pre-equilibrium stage of pA collisions at the LHC

Abstract

We simulate the real-time evolution of the $SU(3)$-glasma generated in the early stages of high-energy proton-nucleus collisions, employing classical lattice gauge theory techniques. Our setup incorporates a realistic modeling of the proton's internal structure and includes longitudinal fluctuations in the initial state, enabling the study of genuinely non-boost-invariant collision dynamics. Focusing on the momentum and angular momentum anisotropies of heavy quarks in the infinite mass limit, we find that the system retains significant anisotropy well beyond the characteristic timescale $\tau = 1/Q_s$. This persistence of anisotropy is further confirmed in the more realistic, non-boost-invariant scenario, across a range of fluctuation amplitudes. These findings pave the way for future investigations involving dynamical heavy quarks and more quantitative initializations of the glasma.