Entropy production in pp and Pb-Pb collisions at the LHC


We use experimentally measured identified particle spectra and Hanbury Brown-Twiss radii to determine the entropy per unit rapidity dS/dy produced in s√=7 TeV pp and sNN−−−√=2.76 TeV Pb-Pb collisions. We find that dS/dy=11335±1188 in 0-10% Pb-Pb, dS/dy=135.7±17.9 in high-multiplicity pp, and dS/dy=37.8±3.7 in minimum bias pp collisions and compare the corresponding entropy per charged particle (dS/dy)/(dNch/dy) to predictions of statistical models. Finally, we use the QCD kinetic theory pre-equilibrium and viscous hydrodynamics to model entropy production in the collision and reconstruct the average temperature profile at τ0=1 fm/c for high multiplicity pp and Pb-Pb collisions.