Precision Dijet Acoplanarity Tomography of the Chromo Structure of Perfect QCD Fluids

Abstract

Dijet acoplanarity is dominated by vacuum (Sudakov) pQCD radiation even in Pb+Pb collisions, but future higher precision measurements of the tails of the acoplanarity distributions can help to resolve {\em separately} the medium opacity, $χ=L/λ$, and the color screening scale $μ^2$ from the path averaged BDMS saturation scale $Q_s^2[χ,μ]=\int dL\; \hat{q}(E,T(L))\propto μ^2 L/λ$, that is already well constrained by nuclear modification factor data on $R_{AA}(p_T)$. We compare Gaussian (BDMS) and non-Gaussian (GLV) models of medium broadening of vacuum (Sudakov) induced acoplanarity distributions in A+A. With few percent accuracy on the ratio of A+A to p+p distributions, experiments can easily identify non-Gaussian Landau and Rutherford tails due to multiple collisions. However, we find that sub-percent precision will be required to constrain $χ$ and $μ$ separately from $Q_s$.

Final version accepted by Nucl.Phys.A for Proc. Quark Matter 2018, Venice, 4 pages, 4 figures