Prasad Hegde

Chiral and deconfinement aspects of the QCD transition

We present results on the chiral and deconfinement properties of the QCD transition at finite temperature. Calculations are performed with 2 + 1 flavors of quarks using the p4, asqtad, and HISQ/tree actions. Lattices with temporal extent N-tau = 6, 8, and 12 are used to understand and control discretization errors and to reliably extrapolate estimates obtained at finite lattice spacings to the continuum limit. The chiral transition temperature is defined in terms of the phase transition in a theory with two massless flavors and analyzed using O(N) scaling fits to the chiral condensate and susceptibility. We find consistent estimates from the HISQ/tree and asqtad actions and our main result is T-c = 154 +/- 9 MeV.

Fluctuations and correlations of net baryon number, electric charge, and strangeness: A comparison of lattice QCD results with the hadron resonance gas model

We calculate the quadratic fluctuations of net baryon number, electric charge and strangeness as well as correlations among these conserved charges in (2+1)-flavor lattice QCD at zero chemical potential. Results are obtained using calculations with tree level improved gauge and the highly improved staggered quark (HISQ) actions with almost physical light and strange quark masses at three different values of the lattice cut-off. Our choice of parameters corresponds to a value of 160 MeV for the lightest pseudo scalar Goldstone mass and a physical value of the kaon mass. The three diagonal charge susceptibilities and the correlations among conserved charges have been extrapolated to the continuum limit in the temperature interval 150 MeV <T < 250 MeV. We compare our results with the hadron resonance gas (HRG) model calculations and find agreement with HRG model results only for temperatures T<= 150 MeV. We observe significant deviations in the temperature range 160 MeV < T < 170 MeV and qualitative differences in the behavior of the three conserved charge sectors. At T < 160 MeV quadratic net baryon number fluctuations in QCD agree with HRG model calculations while, the net electric charge fluctuations in QCD are about 10% smaller and net strangeness fluctuations are about 20% larger. These findings are relevant to the discussion of freeze-out conditions in relativistic heavy ion collisions.

The chiral transition and

We present results on both the restoration of the spontaneously broken chiralsymmetry and the effective restoration of the anomalously broken U(1)_Asymmetry in finite temperature QCD at zero chemical potential using latticeQCD. We employ domain wall fermions on lattices with fixed temporal extentN_\tau = 8 and spatial extent N_\sigma = 16 in a temperature range of T = 139 -195 MeV, corresponding to lattice spacings of a \approx 0.12 - 0.18 fm. Inthese calculations, we include two degenerate light quarks and a strange quarkat fixed pion mass m_\pi = 200 MeV. The strange quark mass is set near itsphysical value. We also present results from a second set of finite temperaturegauge configurations at the same volume and temporal extent with slightlyheavier pion mass. To study chiral symmetry restoration, we calculate thechiral condensate, the disconnected chiral susceptibility, and susceptibilitiesin several meson channels of different quantum numbers. To study U(1)_Arestoration, we calculate spatial correlators in the scalar and pseudo-scalarchannels, as well as the corresponding susceptibilities. Furthermore, we alsoshow results for the eigenvalue spectrum of the Dirac operator as a function oftemperature, which can be connected to both U(1)_A and chiral symmetryrestoration via Banks-Casher relations.

U(1)_A

We studied the QCD phase transition as a function of quark mass in the

symmetry restoration from lattice QCD using Domain Wall Fermions

N_f=3

Exploring phase diagram of

QCD at vanishing baryon density. Lattice simulations have been performed using Highly Improved Staggered Quarks on

N_f=3

N_{\tau}=6

QCD at

lattices with quark masses that correspond to pion masses in the region

\mu=0

80 \lesssim m_{\pi} \lesssim 230

with HISQ fermions

MeV. We found no evidence of the first order phase transition in the current pion mass window. The pion mass at the critical point where the first order phase transition starts is estimated to be