C. Ratti

QCD equation of state at nonzero chemical potential: continuum results with physical quark masses at order μ 2

A bstractWe determine the equation of state of QCD for nonzero chemical potentials via a Taylor expansion of the pressure. The results are obtained for Nf = 2 + 1 flavors of quarks with physical masses, on various lattice spacings. We present results for the pressure, interaction measure, energy density, entropy density, and the speed of sound for small chemical potentials. At low temperatures we compare our results with the Hadron Resonance Gas model. We also express our observables along trajectories of constant entropy over particle number. A simple parameterization is given (the Matlab/Octave script parameterization.m, submitted to the arXiv along with the paper), which can be used to reconstruct the observables as functions of T and μ, or as functions of T and S/N.

Fluctuations and correlations in high temperature QCD

We calculate second- and fourth-order cumulants of conserved charges in a temperature range stretching from the QCD transition region towards the realm of (resummed) perturbation theory. We perform lattice simulations with staggered quarks; the continuum extrapolation is based on

Impact of resonance regeneration and decay on the net proton fluctuations in a hadron resonance gas

N_t=10\dots24

The QCD equation of state at finite density from analytical continuation

in the crossover-region and

Towards the QCD phase diagram from analytical continuation

N_t=8\dots16

Polyakov loop and gluon quasiparticles: A self-consistent approach to Yang–Mills thermodynamics

at higher temperatures. We find that the Hadron Resonance Gas model predictions describe the lattice data rather well in the confined phase. At high temperatures (above

Determination of freeze-out conditions from fluctuation observables measured at RHIC

\sim

Lattice QCD: bulk and transport properties of QCD matter

250 MeV) we find agreement with the three-loop Hard Thermal Loop results.

Production of charge in heavy ion collisions

We investigate net proton fluctuations as important observables measured in heavy-ion collisions within the hadron resonance gas (HRG) model. Special emphasis is given to effects which are a priori not inherent in a thermally and chemically equilibrated HRG approach. In particular, we point out the importance of taking into account the successive regeneration and decay of resonances after the chemical freeze-out, which lead to a randomization of the isospin of nucleons and thus to additional fluctuations in the net proton number. We find good agreement between our model results and the recent STAR measurements of the higher-order moments of the net proton distribution.

Fluctuations of conserved charges on the lattice and in heavy ion collisions

Abstract We want to study thermodynamical observables at finite density. Since direct lattice simulations at finite μ B are hindered by the sign problem an efficient way to study the QCD phase diagram at small finite density is to extrapolate observables from imaginary chemical potential. In this talk we present results on several observables for the equation of state. The observables are calculated along the isentropic trajectories in the (T, μ B ) plane corresponding to the RHIC Beam Energy Scan collision energies. The simulations are performed at the physical mass for the light and strange quarks. μ S was tuned in a way to enforce strangeness neutrality to match the experimental conditions; the results are continuum extrapolated and systematic effects are taken into account for the error estimate.