Accelerating hydrodynamic description of pseudorapidity density and the initial energy density in p+p, Cu+Cu, Au+Au, and Pb+Pb collisions at RHIC and LHC

A known class of analytic, exact, accelerating solutions of prefect relativistic hydrodynamics with longitudinal acceleration is utilized to describe results on the pseudorapidity distributions for different collision systems. These results include $dN\mathrm{/}d\eta$ measured in p+p, Cu+Cu, Au+Au, and Pb+Pb collisions at RHIC and LHC, in a broad centrality range. Going beyond the traditional Bjorken model, from the accelerating hydrodynamic description we determine the initial energy density and other thermodynamic quantities in those collisions.