Gauge invariant momentum broadening of hard probes in glasma

Abstract

We compute the transport coefficient $\hat q$ which quantifies the transverse momentum broadening of hard probes passing through the evolving glasma from the earliest stage of relativistic heavy-ion collisions. We use a proper-time expansion method which is designed to study the glasma at very early times. In our earlier calculations of $\hat q$ we used an approximation that greatly simplifies the complexity of the calculation but introduces a violation of gauge invariance. Based on these results we argued that the glasma plays an important role in jet quenching. In this paper we have used a gauge invariant formulation to calculate $\hat q$. The results for the momentum broadening coefficient are quantitatively very close to those of our previous simplified version of the calculation and confirm our earlier conclusion about the importance of the glasma contribution to jet quenching.

Figures (5)

• Figure 1: A contour plot of $1 - \langle \! \langle W(t,t') \rangle \! \rangle_4$ as a function of $t$ and $t'$ both in fm.
• Figure 2: $1- \langle \! \langle W(t,t'=0) \rangle \! \rangle$ as a function of $t$ in fm at the second, fourth and incomplete fourth orders of the proper time expansion (see text for further explanation).
• Figure 3: The momentum broadening coefficient $\hat{q}$ in GeV$^2$/fm versus time in fm. The solid lines show the result obtained in Carrington:2022bnv with $W = \mathds{1}$ and the dashed lines are the results from the gauge invariant calculation.
• Figure 4: A close-up of the central region in Fig. \ref{['plot-FWF']}.
• Figure 5: The momentum broadening coefficient $\hat{q}$ in GeV$^2$/fm versus time in fm. The coefficient is computed with $W = \mathds{1}$, using the original regularization method (solid lines) and the new method (dashed lines). The dashed pink line is not visible because it is directly under the solid pink line.