Transverse momentum broadening in real-time lattice simulations of the glasma

TL;DR

This paper presents lattice simulations of partons moving through the early glasma stage in heavy-ion collisions, revealing rapid transverse momentum broadening and anisotropy linked to initial color flux tube correlations.

Contribution

It provides the first non-perturbative numerical study of transverse momentum broadening in the glasma, highlighting anisotropic effects and their origin.

Findings

Partons quickly reach saturation momentum during glasma traversal.

Anisotropic transverse momentum broadening observed, larger in rapidity.

Correlation among color flux tubes explains the anisotropy.

Abstract

The study of jets in heavy-ion collisions provides important information about the interaction of partons with the medium that they traverse. The seeds of jets are highly energetic partons, which are produced from hard scatterings during the collision event. As such, they are affected by all different stages of the medium's time evolution, including the glasma, which is the pre-equilibrium precursor state of the quark-gluon plasma. Here we report on our numerical lattice simulations of partons traversing the boost-invariant, non-perturbative glasma as created at the early stages of collisions at RHIC and LHC. We find that partons quickly accumulate transverse momentum up to the saturation momentum during the glasma stage. Furthermore, we observe an interesting anisotropy in transverse momentum broadening of partons with larger broadening in the rapidity than in the azimuthal direction. Its origin can be related to correlations among the longitudinal color-electric and color-magnetic flux tubes in the initial state of the glasma. We compare these observations to the semi-analytic results obtained by a weak-field approximation, where we also find such an anisotropy in a parton's transverse momentum broadening.