118595328
QCD at finite chemical potential with six time slices
We investigate the Taylor expansion of the baryon number susceptibility, and hence, pressure, in a series in the baryon chemical potential ({mu}{sub B}) through a lattice simulation with two flavors of light dynamical staggered quarks at a finer lattice cutoff a=1/6T. We determine the QCD cross over coupling at {mu}{sub B}=0. We find the radius of convergence of the series at various temperatures, and bound the location of the QCD critical point to be T{sup E}/T{sub c}{approx_equal}0.94 and {mu}{sub B}{sup E}/T<1.8. We also investigate the extrapolation of various susceptibilities and linkages to finite chemical potential.
121387686
Hybrid Monte Carlo simulations of a two-dimensional gauge theory
Through a study of the dynamics of the two-dimensional U(1) pure gauge theory we find exponential slowing down in barrier penetration problems. We verify that the dynamical critical exponent in HMC can be tuned exactly to 1, and that normal and gauge fixed updates have equal cost.
123004962
Flavour degrees of freedom and the transition temperature in QCD
We study the finite temperature transition in QCD with four flavours of dynamical quarks. Our simulation is performed on an 8×16 3 lattice for quarks of mass ma=0.01. At the coupling β c =5.15, we find long-lived metastable states, as well as an abrupt change in the entropy density, suggesting a first order phase transition. Using presently available results from corresponding calculations of the hadron masses and the chiral condensate, this gives us a transition temperature T c ≅100 MeV, which is a factor two lower than the transition temperature found in quenched QCD.
17443615
Lattice QCD for RHIC
I briefly introduce the methods by which lattice QCD predictions for RHIC are obtained. Next I deal with lattice determinations of strangeness production and event-to-event fluctuations of conserved quantities. I also present a new diagrammatic method for computing derivatives with respect to chemical potentials, and conclude with discussions of some tests of thermal perturbation theory which follow.
122166973
The phase diagram of QCD: methods and logic of the comparison of experiments and theory
Abstract A small review of the phase diagram of QCD is presented. This is followed by a discussion of the conditions under which experimental data on the fluctuations of conserved quantities in heavy-ion collisions can be treated in the grand canonical ensemble. A robust method for detecting the presence of a nearby critical point in experiments is given. There is a short discussion of the need for non-Gaussian error analysis.
119431013
A precise determination of T_c in QCD from scaling
Existing lattice data on the QCD phase transition are analyzed in renormalized perturbation theory. In quenched QCD it is found that T_c scales for lattices with only 3 time slices, and that T_c/Lambda_msbar=1.15 \pm 0.05. A preliminary estimate in QCD with two flavours of dynamical quarks shows that this ratio depends on the quark mass. For realistic quark masses we estimate T_c/Lambda_msbar=0.49 \pm 0.02. We also investigate the equation of state in quenched QCD at 1-loop order in renormalised perturbation theory.
13890009
Caloric curves for small systems in the nuclear lattice gas model
For pedagogical reasons we compute the caloric curve for 11 particles in a ${3}^{3}$ lattice. Monte Carlo simulation can be avoided and exact results are obtained. We compare canonical and microcanonical results for the caloric curve. Even down to this small system, agreement between the canonical model and the microcanonical model is surprisingly good. We point out that the introduction of kinetic energy in the nuclear lattice gas model modifies the results of the standard lattice gas model in a profound way. The model is also used to test the accuracy of the saddle-point approximation for density of states.
121044914
RENORMALIZATION OF QUANTUM CHROMODYNAMICS
Renormalization of quantum chromodynamics is carried out by means of a momentum-space subtraction scheme, which is computationally simple, provides a well-defined procedure for the determination of renormalization constants, and is equally applicable to light and heavy quarks. We also obtain the renormalization-group parameters, verify the decoupling theorem for heavy quarks, and compute the effective coupling constant and effective quark masses.
118808591
A soluble statistical model for nuclear fragmentation
The statistical model of Chase and Mekjian, which offers an analytic solution for the canonical ensemble of non-interacting fragments, is investigated for it's thermodynamic behavior. Various properties of the model, which exhibits a first-order phase transition, are studied. The effects of finite particle number are investigated. Three extensions of the model are considered, excluded volume, Coulomb effects and inclusion of isospin degrees of freedom. A formulation of a microcanonical version of the model is also presented.
118245922
Cygnus experiment at Los Alamos
The Cygnus experiment at Los Alamos National Laboratory has been designed to study, with high angular accuracy, point sources of gamma rays of energy above 1014 eV. The experimental detector consists of an air shower array to observe gamma-ray showers and a shielded, large-area track detector to study the muon content of the showers. In this paper we present preliminary data from the array and describe its performance.
121663425
Quantum-chromodynamic potential model for light and heavy quarkonia
Our earlier treatment for the investigation of the cc-bar, bb-bar, and tt-bar spectra is extended to other p quarkonia with u, d, s, c, and b quarks. We find that it is possible to account fully for the observed ground-state hyperfine splittings of light as well as heavy quarkonia provided that the perturbative quantum-chromodynamic potential is supplemented not only by the nonperturbative confining potential but also by a nonperturbative annihilation potential which rapidly decreases with increase in the quark mass. We also give our predictions for the experimentally interesting bu-bar, bs-bar, and bc-bar systems with unknown mass splittings.