Modification of Z Boson Properties in Quark-Gluon Plasma

We calculate the change in the effective mass and width of a Z boson in the environment of a quark-gluon plasma under the conditions expected in Pb-Pb collisions at the LHC. The change in width is predicted to be only about 1 MeV at a temperature of 1 GeV, compared to the natural width of 2490$\pm$7 MeV. The mass shift is even smaller. Hence no observable effects are to be expected.Comment: 7 pages latex file with 6 embedded PS figure

Inhomogeneous Nucleation of Quark-Gluon Plasma in High Energy Nuclear Collisions

We estimate the probability that a hard nucleon-nucleon collision is able to nucleate a seed of quark--gluon plasma in the surrounding hot and dense hadronic matter formed during a central collision of two large nuclei at AGS energies. The probability of producing at least one such seed is on the order of 1-100\%. We investigate the influence of quark--gluon plasma formation on the observed multiplicity distribution and find that it may lead to noticable structure in the form of a bump or shoulder.Comment: 16 pages, latex and 12 ps figures available on reques

Thermal rates for baryon and anti-baryon production

We use a form of the fluctuation-dissipation theorem to derive formulas giving the rate of production of spin-1/2 baryons in terms of the fluctuations of either meson or quark fields. The most general formulas do not assume thermal or chemical equilibrium. When evaluated in a thermal ensemble we find equilibration times on the order of 10 fm/c near the critical temperature in QCD.Comment: 22 pages, 4 tables and 2 figures, REVTe

On the imaginary parts and infrared divergences of two-loop vector boson self-energies in thermal QCD

We calculate the imaginary part of the retarded two-loop self-energy of a static vector boson in a plasma of quarks and gluons of temperature T, using the imaginary time formalism. We recombine various cuts of the self-energy to generate physical processes. We demonstrate how cuts containing loops may be reinterpreted in terms of interference between Order $\alpha$ tree diagrams and the Born term along with spectators from the medium. We apply our results to the rate of dilepton production in the limit of dilepton invariant mass E>>T. We find that all infrared and collinear singularities cancel in the final result obtained in this limit.Comment: references added, typos corrected, slightly abridged, version accepted for publication in Phys. Rev.

Bremsstrahlung from a Microscopic Model of Relativistic Heavy Ion Collisions

We compute bremsstrahlung arising from the acceleration of individual charged baryons and mesons during the time evolution of high-energy Au+Au collisions at the Relativistic Heavy Ion Collider using a microscopic transport model. We elucidate the connection between bremsstrahlung and charge stopping by colliding artificial pure proton on pure neutron nuclei. From the intensity of low energy bremsstrahlung, the time scale and the degree of stopping could be accurately extracted without measuring any hadronic observables.Comment: 25 pages using revtex with 9 embedded EPS figures, modified somewhat the discussion on the method in sect. II B, to appear in Phys. Rev.

Fixed Charge Ensembles and Parity Breaking Terms

Recently derived results for the exact induced parity-breaking term in 2+1 dimensions at finite temperature are shown to be relevant to the determination of the free energy for fixed-charge ensembles. The partition functions for fixed total charge corresponding to massive fermions in the presence of Abelian and non-Abelian magnetic fields are discussed. We show that the presence of the induced Chern-Simons term manifests itself in that the free energy depends strongly on the relation between the external magnetic flux and the value of the fixed charge.Comment: 10 pages, Revte

Lorentz-violating contributions of the Carroll-Field-Jackiw model to the CMB anisotropy

We study the finite temperature properties of the Maxwell-Carroll-Field-Jackiw (MCFJ) electrodynamics for a purely spacelike background. Starting from the associated finite temperature partition function, a modified black body spectral distribution is obtained. We thus show that, if the CMB radiation is described by this model, the spectrum presents an anisotropic angular energy density distribution. We show, at leading order, that the Lorentz-breaking contributions for the Planck's radiation law and for the Stefan-Boltzmann's law are nonlinear in frequency and quadratic in temperature, respectively. Using our results, we set up bounds for the Lorentz-breaking parameter, and show that Lorentz violation in the context of the MCFJ model is unable to yield the known CMB anisotropy (of 1 part in $10^{5})$

Leptogenesis from Pseudo-Scalar Driven Inflation

We examine recent claims for a considerable amount of leptogenesis, in some inflationary scenarios, through the gravitational anomaly in the lepton number current. We find that when the short distances contributions are properly included the amount of lepton number generated is actually much smaller.Comment: JHEP style, 11 pages. Corrected typ

Effects from inhomogeneities in the chiral transition

We consider an approximation procedure to evaluate the finite-temperature one-loop fermionic density in the presence of a chiral background field which systematically incorporates effects from inhomogeneities in the chiral field through a derivative expansion. We apply the method to the case of a simple low-energy effective chiral model which is commonly used in the study of the chiral phase transition, the linear sigma-model coupled to quarks. The modifications in the effective potential and their consequences for the bubble nucleation process are discussed.Comment: 11 pages, 5 figures. v2: appendix and references added, published versio