Pseudorapidity and centrality dependence of energy flow in 2.76TeV PbPb collisions

A measurement of the transverse energy flow over a broad range of pseudorapidity ($|\eta|\!<\!$~4.9) and centrality for PbPb collisions at a center of mass energy per nucleon pair $\sqrt{s_{\rm NN}}$~=~2.76 TeV is presented. For central collisions $dE_T/d\eta$ exceeds 2~TeV at $\eta = 0$. From this maximum $dE_T/d\eta$ falls by a factor of 2 by $\eta \approx 4$. These results are compared to lower energy data and CMS multiplicity measurements. At central pseudorapidity the transverse energy per participant is above predictions based on lower energy data that assume a logarithmic scaling with centre of mass energy. The hot dense system created by the PbPb collisions likely expands rapidly, and measuring the energy flow over a very wide range of angles can constrain the initial pressure and the equation of state of the expanding matter. The energy flow from truly heavy ion collisions has not been measured over a broad pseudorapdity range for center of mass energies above 8~GeV.