arXiv subjects

Peter Petreczky

Publications and source records attributed to Peter Petreczky.

At least 127 records · Page 7Linked to original sources

arXiv2014

Equation of state at finite net-baryon density using Taylor coefficients up to sixth order

We employ the lattice QCD data on Taylor expansion coefficients up to sixth order to construct an equation of state at finite net-baryon density. When we take into account how hadron masses depend on lattice spacing and quark mass, the coefficients evaluated using the p4 action are equal to those of hadron resonance gas at low temperature. Thus the parametrised equation of state can be smoothly connected to the hadron resonance gas equation of state. We see that the equation of state using Taylor coefficients up to second order is realistic only at low densities, and that at densities corresponding to s/n_B > 40, the expansion converges by the sixth order term.

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arXiv2013

Lattice NRQCD study of in-medium bottomonium states using $N_f = 2+1, 48^3 \times 12$ HotQCD configurations

The behavior of bottomonium state correlators at non-zero temperature, $140.4 (β= 6.664) \le T \le 221 (β= 7.280)$ (MeV), where the transition temperature is $154(9)$ (MeV), is studied, using lattice NRQCD on $48^3 \times 12$ HotQCD HiSQ action configurations with light dynamical $N_f = 2 + 1$ ($m_{u,s}/m_s = 0.05$) staggered quarks. In order to understand finite temperature effects on quarkonium states, zero temperature behavior of bottomonium correlators is compared based on $32^4$ ($β= 6.664, 6.800$ and $6.950$) and $48^3 \times 64$ ($β= 7.280)$ lattices. We find that temperature effects on S-wave bottomonium states are small but P-wave bottomonium states show a noticeable temperature dependence above the transition temperature.

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arXiv2013

Quarkonia in the Quark Gluon Plasma

In this paper we review recent progress towards understanding the nature of quarkonia in the quark-gluon plasma. We review the theory necessary to understand the melting of bound states due to color-screening, including lattice results for the heavy quark potential, lattice results on the correlation functions related to the relevant spectral functions, and the emergence of a complex-valued potential in high-temperature quantum chromodynamics. We close with a brief survey of phenomenological models of quarkonium suppression in relativistic heavy ion collisions.

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arXiv2012

Determination of alpha_s from the QCD static energy

We compare lattice data for the short-distance part of the static energy in 2+1 flavor quantum chromodynamics (QCD) with perturbative calculations, up to next-to-next-to-next-to leading-logarithmic accuracy. We show that perturbation theory describes very well the lattice data at short distances, and exploit this fact to obtain a determination of the product of the lattice scale r_0 with the QCD scale Lambda_{MS}. With the input of the value of r_0, this provides a determination of the strong coupling alpha_s at the typical distance scale of the lattice data. We obtain alpha_s(1.5 GeV)=0.326\pm0.019, which provides a novel determination of alpha_s at low energy and with three-loop accuracy (including resummation of the leading ultrasoft logarithms). When this value is evolved to the Z-mass scale M_Z, it corresponds to alpha_s(M_Z)=0.1156^{+0.0021}_{-0.0022}.

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arXiv2012

Equation of state at non-zero baryon density based on lattice QCD

We employ the lattice QCD data on Taylor expansion coefficients to extend our previous parametrization of the equation of state to finite baryon density. When we take into account lattice spacing and quark mass dependence of the hadron masses, the Taylor coefficients at low temperature are equal to those of hadron resonance gas. Parametrized lattice equation of state can thus be smoothly connected to the hadron resonance gas equation of state at low temperatures.

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arXiv2011

Equation of state at finite baryon density based on lattice QCD

We employ the lattice QCD data on Taylor expansion coefficients to extend our previous parametrization of the equation of state to finite baryon density. When we take into account lattice spacing and quark mass dependence of the hadron masses, the Taylor coefficients at low temperature are equal to those of hadron resonance gas. Thus the equation of state is smoothly connected to the hadron resonance gas equation of state at low temperatures. We also show how the elliptic flow is affected by this equation of state at the maximum SPS energy.

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arXiv2010

Taste symmetry and QCD thermodynamics with improved staggered fermions

Taste symmetry violations in staggered fermion formulations correlate strongly with the cut-off (lattice spacing) dependence in thermodynamic quantities. Better taste symmetry on the lattice can be achieved either by decreasing the lattice spacing and going to larger temporal extent in finite-temperature calculations, or by further improving the action. The highly improved staggered quark (HISQ) action offers a further degree of improvement and substantially reduces taste violations. We report on our studies of the 2+1 flavor QCD thermodynamics with the HISQ/tree action. By systematically comparing HISQ/tree, asqtad, p4 and stout calculations we quantify how the cut-off effects manifest themselves in different thermodynamic quantities, including the renormalized Polyakov loop, chiral condensate, various fluctuations and correlations of conserved charges. The implications for the equation of state and a comparison to the hadron resonance gas model are also discussed. The chiral aspects of the finite-temperature transition are discussed in the companion HotQCD contribution [1].

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arXiv2010

Polyakov loop and correlator of Polyakov loops at next-to-next-to-leading order

We study the Polyakov loop and the correlator of two Polyakov loops at finite temperature in the weak-coupling regime. We calculate the Polyakov loop at order g^4. The calculation of the correlator of two Polyakov loops is performed at distances shorter than the inverse of the temperature and for electric screening masses larger than the Coulomb potential. In this regime, it is accurate up to order g^6. We also evaluate the Polyakov-loop correlator in an effective field theory framework that takes advantage of the hierarchy of energy scales in the problem and makes explicit the bound-state dynamics. In the effective field theory framework, we show that the Polyakov-loop correlator is at leading order in the multipole expansion the sum of a colour-singlet and a colour-octet quark-antiquark correlator, which are gauge invariant, and compute the corresponding colour-singlet and colour-octet free energies.

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arXiv2010

Deconfinement and chiral transition with the highly improved staggered quark (HISQ) action

We report on investigations of the chiral and deconfinement aspects of the finite temperature transition in 2+1 flavor QCD using the Highly Improved Staggered Quark (HISQ) action on lattices with temporal extent $N_τ=6$ and $N_τ=8$. We have performed the calculations for physical values of the strange quark mass $m_s$ and the light quark masses $m_l=0.2m_s$ and $0.05m_s$. Several finite temperature observables, including the renormalized Polyakov loop, the renormalized chiral condensate and the chiral susceptibility have been calculated. We also study the fluctuations and correlations of different conserved charges as well as the trace anomaly at finite temperature. We compare our findings with previous calculations that use different improved staggered fermion formulations: asqtad, p4 and stout.

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arXiv2010

On Fluctuations of Conserved Charges : Lattice Results Versus Hadron Resonance Gas

We compare recent lattice results on fluctuations and correlations of strangeness, baryon number and electric charge obtained with p4 improved staggered action with the prediction of hadron resonance gas model. We show that hadron resonance gas can describe these fluctuations reasonably well if the hadron properties are as calculated on the lattice.

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arXiv2009

First results on QCD thermodynamics with HISQ action

We report on investigations of the chiral and deconfinement aspects of the finite temperature transition in 2+1 flavor QCD using the Highly Improved Staggered Quark (HISQ) action on lattices with temporal extent $N_τ=6$ and $N_τ=8$. We have calculated several physical observables, including the renormalized Polyakov loop, strangeness fluctuations, the renormalized chiral condensate and the chiral susceptibility in the crossover region for physical values of the strange quark mass $m_s$ and light quark masses $m_l=0.2m_s$ and $0.05m_s$. We compare our findings with previous calculations that use different improved staggered fermion formulations: asqtad, p4 and stout.

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arXiv2009

Quark number fluctuations at high temperatures

We calculate the second, fourth and sixth order quark number fluctuations in the deconfined phase of 2+1 flavor QCD using lattices with temporal extent Nt=4, 6, 8 and 12. We consider light, strange and charm quarks. We use p4 action for valence quarks and gauge configurations generated with p4 action with physical value of the strange quark mass and light quark mass mq=0.1ms generated by the RBC-Bielefeld collaboration. We observe that for all quark masses the quark number fluctuations rapidly get close to the corresponding ideal gas limits. We compare our results to predictions of a quasi-particle model and resummed high temperature perturbative calculations. We also investigate correlations among different flavor channels.

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arXiv2009

Recent progress in lattice QCD at finite temperature

I review recent progress in finite temperature lattice calculations, including the study of the nature of the deconfinement transition in QCD, equation of state, screening of static quarks and meson spectral functions.

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arXiv2009

Quarkonium at Finite Temperature

We discuss properties of heavy quarkonium states at high temperatures based on lattice QCD and potential models. We review recent progress made in lattice calculations of spatial static quark anti-quark correlators as well as quarkonium correlators in Euclidean time. Recent developments in effective field theory approach and potential models are also discussed.

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arXiv2008

Color singlet and adjoint free energy at finite temperature

We study correlation functions of static quark-antiquark pairs in SU(2) gauge theory at finite temperature. By measuring Polyakov loop correlators and temporal Wilson loops with APE smearing of spatial links we are able to give consistent definitions of the singlet and adjoint free energies at short distances, where the notion of these free energies is meaningful. APE smearing procedure allows to achieve a high degree of overlap in the singlet channel and to reconstruct the adjoint part from the color averaged and singlet free energy.

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arXiv2008

Zero mode contribution in quarkonium correlators and in-medium properties of heavy quarks

We calculate the low energy contribution to quarkonium correlators in Euclidean time in lattice QCD. This contribution was found to give the dominant source of the temperature dependence of the correlators. We have found that the low energy contribution is well described by a quasi-particle model and have determined the effective temperature dependent heavy quark mass.

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arXiv2008

Static quark-antiquark pairs at finite temperature

In a framework that makes close contact with modern effective field theories for non-relativistic bound states at zero temperature, we study the real-time evolution of a static quark-antiquark pair in a medium of gluons and light quarks at finite temperature. For temperatures ranging from values larger to smaller than the inverse distance of the quark and antiquark, 1/r, and at short distances, we derive the potential between the two static sources, and calculate their energy and thermal decay width. Two mechanisms contribute to the thermal decay width: the imaginary part of the gluon self energy induced by the Landau damping phenomenon, and the quark-antiquark color singlet to color octet thermal break up. Parametrically, the first mechanism dominates for temperatures such that the Debye mass is larger than the binding energy, while the latter, which we quantify here for the first time, dominates for temperatures such that the Debye mass is smaller than the binding energy. If the Debye mass is of the same order as 1/r, our results are in agreement with a recent calculation of the static Wilson loop at finite temperature. For temperatures smaller than 1/r, we find new contributions to the potential, both real and imaginary, which may be relevant to understand the onset of heavy quarkonium dissociation in a thermal medium.

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arXiv2007

Can quarkonia survive deconfinement ?

We study quarkonium correlators and spectral functions at zero and finite temperature in QCD with only heavy quarks using potential models combined with perturbative QCD. First, we show that this approach can describe the quarkonium correlation function at zero temperature. Using a class of screened potentials based on lattice calculations of the static quark-antiquark free energy we calculate spectral functions at finite temperature. We find that all quarkonium states, with the exception of the $1S$ bottomonium, dissolve in the deconfined phase at temperatures smaller than $1.5T_c$, in contradiction with the conclusions of recent studies. Despite this the temperature dependence of the quarkonium correlation functions calculated on the lattice is well reproduced in our model. We also find that even in the absence of resonances the spectral function at high temperatures is significantly enhanced over the spectral function corresponding to free quark antiquark propagation.

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