Speaker
Dr
Prasad Hegde
(Central China Normal University)
Description
Hydrodynamic models of heavy-ion collisions have increasingly begun to rely on lattice results for the Equation of State. While the lattice has the advantage of being a first-principles approach to QCD, the notorious sign problem prevents a direct determination of the equation of state and other thermodynamic observables at finite chemical potential $\mu_B$.
Quark number susceptibilities allow us to extrapolate the equation of state in a controlled way to small values of $\mu_B$ based on calculations at $\mu_B=0$. Such an extrapolation is necessary in order to accurately describe the results from the beam energy scan at RHIC and from the LHC where typically $\mu_B/T=0.1$-4, depending upon the energy of the beam.
In our talk, we will present results from a high-statistics calculation of all the Taylor coefficients upto sixth order in a $(\mu_B,\mu_Q,\mu_S)$-expansion of the pressure. Our calculation allows us to extrapolate, for the first time, the equation of state on the freezeout curve upto $\mathcal{O}(\mu_B^4)$ while our sixth-order results show that the truncation error is not more than a few \% upto $\mu_B/T\sim1.5$. Thus our equation of state should be useful in describing both the LHC results as well as results from RHIC beam energy scan down to $\sqrt{s}\sim$20 GeV. We will also use our results to construct the isentropic equation of state for strangeness-neutral systems.
Our lattice QCD calculations make use of the gauge ensembles generated using the HISQ action. Our lattices sizes range from $6\times24^3$ to $12\times48^3$ and the pion mass ($\sim$160 MeV) is nearly equal to its physical value while the strange quark is at exactly its physical value.
Primary author
Dr
Prasad Hegde
(Central China Normal University)
