Time-Dependent Observables in Heavy Ion Collisions I: Setting up the Formalism

Understand

We adapt the Schwinger-Keldysh formalism to study heavy-ion collisions in perturbative QCD.

• Employing the formalism, we calculate the two-point gluon correlation function $G_{22}^{a\mu,b\nu}$ due to the lowest-order classical gluon fields in the McLerran-Venugopalan model of heavy ion collisions and observe an interesting transition from the classical fields to the quasi-particle picture at later times.
• Motivated by this observation, we push the formalism to higher orders in the coupling and calculate the contribution to $G_{22}^{a\mu,b\nu}$ coming from the diagrams representing a single rescattering between two of the produced gluons.
• We assume that the two gluons go on mass shell both before and after the rescattering.