Screening of heavy quark free energies at finite temperature and non-zero baryon chemical potential

We analyze the dependence of heavy quark free energies on the baryon chemical potential (mu_b) in 2-flavour QCD using improved (p4) staggered fermions with a bare quark mass of m/T = 0.4. By performing a 6th order Taylor expansion in the chemical potential which circumvents the sign problem. The Taylor expansion coefficients of colour singlet and colour averaged free energies are calculated and from this the expansion coefficients for the corresponding screening masses are determined. We find that for small mu_b the free energies of a static quark anti-quark pair decrease in a medium with a net excess of quarks and that screening is well described by a screening mass which increases with increasing mu_b. The mu_b-dependent corrections to the screening masses are well described by perturbation theory for T > 2 T_c. In particular, we find for all temperatures above T_c that the expansion coefficients for singlet and colour averaged screening masses differ by a factor 2.Comment: 14 page

The Problem of Mass: Mesonic Bound States Above T_c

We discuss the problem of mass, noting that meson masses decrease with increasing scale as the dynamically generated condensate of "soft glue" is melted (Brown/Rho scaling). We then extend the Bielefeld LGS color singlet interaction computed for heavy quarks in a model-dependent way by including the Ampere law velocity-velocity interaction. Parameterizing the resulting interaction in terms of effective strength of the potential and including screening, we find that the masses of pi, sigma, rho and A1 excitations, 32 degrees of freedom in all, go to zero (in the chiral limit) as T goes to Tc essentially independently of the input quark (thermal) masses in the range of 1-2 GeV, calculated also in Bielefeld. We discuss other LGS which show q-bar q bound states, which we interpret as our chirally restored mesons, for T > Tc.Comment: 20 pages, 6 figures (Table 2 is added

Heavy quark potential and quarkonia dissociation rates

Quenched lattice data for the quark-antiquark interaction (in terms of heavy quark free energies) in the color singlet channel at finite temperatures are fitted and used within the nonrelativistic Schroedinger equation formalism to obtain binding energies and scattering phase shifts for the lowest eigenstates in the charmonium and bottomonium systems in a hot gluon plasma. The partial dissociation rate due to the Bhanot-Peskin process is calculated using different assumptions for the gluon distribution function, including free massless gluons, massive gluons, and massive damped gluons. It is demonstrated that a temperature dependent gluon mass has an essential influence on the heavy quarkonia dissociation, but that this process alone is insufficient to describe the heavy quarkonia dissociation rates.Comment: 4 pages, 5 figures, contribution to the proceedings of the International Conference on Hard and Electromagnetic Probes of High Energy Nuclear Collisions, Ericeira, Portugal, Nov. 4-10, 200

Dimension 2 condensates and Polyakov Chiral Quark Models

We address a possible relation between the expectation value of the Polyakov loop in pure gluodynamics and full QCD based on Polyakov Chiral Quark Models where constituent quarks and the Polyakov loop are coupled in a minimal way. To this end we use a center symmetry breaking Gaussian model for the Polyakov loop distribution which accurately reproduces gluodynamics data above the phase transition in terms of dimension 2 gluon condensate. The role played by the quantum and local nature of the Polyakov loop is emphasized.Comment: 3 pages, 1 figure. Talk given at the IVth International Conference on Quarks an Nuclear Physics, Madrid, June 5th-10th 200

Book Review - Energy Futures

Review of Russell Gold, The Boom: How Fracking Ignited the American Energy Revolution and Changed the World (New York: Simon & Schuster, 2014

Heavy quark free energies and screening at finite temperature and density

We study the free energies of heavy quarks calculated from Polyakov loop correlation functions in full 2-flavour QCD using the p4-improved staggered fermion action. A small but finite Baryon number density is included via Taylor expansion of the fermion determinant in the Baryo-chemical potential mu. For temperatures above Tc we extract Debye screening masses from the large distance behaviour of the free energies and compare their mu-dependence to perturbative results.Comment: 6 pages, Presented at 23rd International Symposium on Lattice Field Theory (Lattice 2005), Trinity College, Dublin, Ireland, 25-30 Jul 200

Thermodynamics of two-colour QCD

We discuss the thermodynamics of two-colour QCD with four flavours of staggered quarks on 8^3x4 and 16^3x4 lattices. In our simulations we use the Naik action for the fermions and a (1,2) tree-level improved gauge action. We analyze the deconfinement and chiral phase transitions for four different quark masses (m=0.1,0.05,0.025,0.015). Contrary to three-colour QCD the peak in the Polyakov loop susceptibility decreases with decreasing quark mass. This reflects an early breaking of the string in the heavy quark potential, which we verify explicitly by calculating the heavy quark potential at finite temperature using Polyakov loop correlations.Comment: LATTICE98(hightemp), 3 pages, LaTeX2e File, 5 EPS-figures, espcrc2.st

Matter formed at the BNL relativistic heavy ion collider

We suggest that the "new form of matter" found just above $T_c$ by RHIC is made up of tightly bound quark-antiquark pairs, essentially 32 chirally restored (more precisely, nearly massless) mesons of the quantum numbers of $\pi$, $\sigma$, $\rho$ and $a_1$. Taking the results of lattice gauge simulations (LGS) for the color Coulomb potential from the work of the Bielefeld group and feeding this into a relativistic two-body code, after modifying the heavy-quark lattice results so as to include the velocity-velocity interaction, all ground-state eigenvalues of the 32 mesons go to zero at $T_c$ just as they do from below $T_c$ as predicted by the vector manifestation (VM in short) of hidden local symmetry. This could explain the rapid rise in entropy up to $T_c$ found in LGS calculations. We argue that how the dynamics work can be understood from the behavior of the hard and soft glue.Comment: Final versio

String breaking in Lattice QCD

The separation of a heavy quark and antiquark pair leads to the formation of a tube of flux, or string, which should break in the presence of light quark-antiquark pairs. This expected zero temperature phenomenon has proven elusive in simulations of lattice QCD. We present simulation results that show that the string does break in the confining phase at nonzero temperature.Comment: LATTICE98(hightemp), 3 pages, 4 figures, LaTe