Exploring Longitudinal Observables with 3+1D IP-Glasma

We present a formulation of the initial state of heavy ion collisions that generalizes the 2+1D boost invariant IP-Glasma [1] to 3+1D through JIMWLK rapidity evolution of the pre-collision Wilson lines. The rapidity dependence introduced by the JIMWLK evolution leads us to modify the initial condition for the gauge fields, and to solve Gauss' law iteratively in order to allow for temporal evolution on a 3-dimensional lattice. While the transverse physics of QGP has been studied nearly exhaustively, the effect of longitudinal fluctuations introduced by the JIMWLK evolution has yet to be studied in detail phenomenologically. Hence, we couple our 3+1D IP-Glasma model to MUSIC+UrQMD, for completely 3+1D simulations of heavy ion collisions. Specifically, we consider Pb-Pb collisions at root s = 2.76 TeV and study the rapidity dependence of the charged hadron v(n)(eta) via the eta-dependent flow factorization ratios r(n)(eta(a), eta(b)) as measured by CMS [2], as well as the charged hadron multiplicity dN(ch)/d(eta).

Automated summary

The study generalizes the 2+1D IP-Glasma to 3+1D by incorporating JIMWLK rapidity evolution, modifying initial conditions for gauge fields, and iteratively solving Gauss' law on a 3-dimensional lattice. Coupling this model to MUSIC+UrQMD allows for completely 3+1D simulations of heavy ion collisions. The longitudinal fluctuations introduced by JIMWLK evolution have not been extensively studied phenomenologically in the context of heavy ion collisions.