Excess production of low-mass lepton pairs in S+Au collisions at the CERN Super Proton Synchrotron and the quark-hadron phase transition.
The mass distribution for excess dielectrons in S + Au collisions at 200 A GeV measured by the CERES collaboration at CERN Super Proton Synchrotron is analyzed. The data are seen to be in satisfactory agreement with a scenario where a thermalized quark-gluon plasma is formed initially, which expands, cools, hadronizes, and undergoes a freeze out. The same treatment is also seen to provide a reasonable description for the excess dimuons measured by the HELIOS-3 experiment for S + W collisions. There is also a plausible evidence for a small contribution of bremsstrahlung production of low mass dielectrons in the CERES data.

title: Supercooling and final-state effects on dilepton spectra.
abstract: We consider two problems associated with the production of dileptons during collisions between heavy nuclei at the Brookhaven Relativistic Heavy Ion Collider energy. One is the difference in dilepton yield between an idealized Maxwell construction of phase coexistence and a dynamical phase transition with finite nucleation and phase conversion rates. The other is the contribution from dilepton-producing reactions involving free-streaming hadrons in the final state. We find that the mass spectrum in the range 2${\mathit{m}}_{\mathrm{\ensuremath{\pi}}}$M2 GeV is dominated by the mixed phase and the final hadron phase, is somewhat sensitive to the degree of supercooling, but is remarkably insensitive to the ``freeze-out'' temperature which delineates the passage from local thermal equilibrium to free streaming.

title: High-energy photons from passage of jets through Quark-Gluon plasma.
abstract: We calculate the production of high-energy photons from Compton scattering and annihilation of a quark jet passing through a quark gluon plasma produced in a relativistic heavy ion collision. The contributions are large and reflect the momentum distribution of the jets and the initial conditions of the plasma.

title: Photon interferometry of Au+Au collisions at the BNL Relativistic Heavy-Ion Collider.
abstract: We calculate the two-body correlation function of direct photons produced in central Au+Au collisions at the Relativistic Heavy-Ion Collider. Our calculation includes contributions from the early preequilibrium phase in which photons are produced via hard parton scatterings as well as radiation of photons from a thermalized quark-gluon plasma and the subsequent expanding hadron gas. We find that high energy photon interferometry provides a faithful probe of the details of the space-time evolution and of the early reaction stages of the system.

title: Photons and Dileptons at LHC
abstract: We discuss real and virtual photon sources in heavy ion collisions and present results for dilepton yields in Pb+Pb collisions at the LHC at intermediate and large transverse momentum p_T.

title: How relativistic heavy ion collisions can help us understand the universe
abstract: We discuss the anthropic principle and its implications for our existence and the physical laws which govern the universe. Several amazing coincidences which provide conditions necessary for creation of life suggest that the "laws of nature" are not uniquely determined. The idea that our universe is only one among a multitude of universes with different physical laws, as predicted by the theory of chaotic cosmic inflation, provides a logically simple, but speculative resolution of the anthropic principle. An important insight of modern quantum field theory is that the physical laws are not only determined by symmetry principles, but also by the nature of the vacuum state. Experiments involving collisions of relativistic heavy ions provide the clearest tests of the hypothesis that properties of particles and forces can be modified by a change in the vacuum state. We outline the goals of these experiments and briefly review their current status.

title: Microchips as precision quantum-electrodynamic probes.
abstract: We show that QED fluctuations for present metal-oxide-semiconductor field-effect transistor microcircuit devices are substantial and thus cannot be ignored. For example, the Casimir energy of a gate-region capacitor is typically (1/10) of the electrostatic energy. Measurement of their electronic transport properties is suggested as a tool to learn about some nonperturbative aspects of QED which cannot be reached via high-energy or atomic physics.

title: Bloch-Nordsieck regularization of QCD transverse-momentum distributions.
abstract: An expression for transverse-momentum distributions is presented for Drell-Yan-type processes: it is infrared finite, includes soft-gluon summation in the leading-logarithmic approximation and reproduces the first-order perturbative results at large {ital p}{sub {ital T}}. In addition, our expression incorporates soft QCD radiative corrections to that part of the cross section where hard bremsstrahlung dominates. We compute {ital W} transverse-momentum distributions and average values for a set of different energies: {radical}{ital s} =630 GeV, 1.8 TeV, 6 TeV, and 18 TeV.

title: Implications of the chiral anomaly for quantum Hall-effect devices.
abstract: The anomaly equation ${\ensuremath{\partial}}_{\ensuremath{\mu}}$${J}_{5}$${}^{\ensuremath{\mu}}$=-(${e}^{2}$/8${\ensuremath{\pi}}^{2}$ ${\ensuremath{\Elzxh}}^{2}$c) (${F}_{\ensuremath{\lambda}\ensuremath{\sigma}}^{\mathrm{*}}$${F}^{\ensuremath{\lambda}\ensuremath{\sigma}}$) is used to derive a relationship between the filling factor (\ensuremath{\nu}) and the Hall conductance on the gate capacitor of a field-effect-transistor device. In addition, the chiral phase (\ensuremath{\theta}) states are shown to be related to those of the filling factor by \ensuremath{\Vert}\ensuremath{\theta}〉=\ensuremath{\Vert}2\ensuremath{\pi}\ensuremath{\nu}〉.