Entropy production in pp and Pb-Pb collisions at energies available at the CERN Large Hadron Collider

Abstract

We use experimentally measured identified particle spectra and Hanbury Brown-Twiss radii to determine the entropy per unit rapidity $dS/dy$ produced in $\sqrt{s}=7$ TeV pp and $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV Pb-Pb collisions. We find that $dS/dy=11335\pm 1188$ in 0-10% Pb-Pb, $dS/dy=135.7\pm 17.9$ in high-multiplicity pp, and $dS/dy=37.8\pm 3.7$ in minimum bias pp collisions and compare the corresponding entropy per charged particle $(dS/dy)/(d{N}_{\mathrm{ch}}/dy)$ 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 ${\tau }_0=1$ fm/$c$ for high multiplicity pp and Pb-Pb collisions.

Comments: 13 pages, 9 figures; added an appendix on relation between 1D and 3D HBT radii, updated references, small corrections, published version