Transverse flow effects on high-energy photons emitted by expanding quark-gluon plasma.
High-energy photons emitted in ultrarelativistic nucleus-nucleus collisions at energies reached at the CERN SPS and LHC and the BNL RHIC are discussed as a source of information on the collision dynamics and as a signature of the deconfining phase transition. The energy density and velocity fields of the expanding matter have been computed assuming cylindrical symmetry along the transverse direction and boost invariance along the longitudinal direction. The emission of photons from an expanding quark-gluon plasma undergoing a first-order phase transition has been evaluated. When the transverse flow of the system is accounted for, it is found that the photons having their origin in the hadronic matter are comparable to those originating in the quark-gluon plasma for [ital p][sub [ital T]] greater than 2 GeV, at energies reached at the SPS and RHIC. At energies reached at the LHC, photons having a [ital p][sub [ital T]] larger than about 4 GeV are shown to have their origin predominantly in the quark-gluon plasma. The location of the [ital p][sub [ital T]] window is shown to be very sensitive to the value of the freeze-out temperature chosen. The feasibility of evaluating the direct (QCD) photons has been studied. Photons fragmented off final more » state quarks in parton-parton scattering are shown to provide the largest background beyond [ital p][sub [ital T]][approx]3 GeV at energies reached at the LHC. Accounting for hadronic degrees of freedom beyond the pion is found to be important. « less

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: 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: 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: 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: Bounds on compositeness from neutrinoless double beta decay.
abstract: Assuming the existence of a heavy Majorana neutral particle arising from a composite model scenario we discuss the constraints imposed by present experimental limits of half-life neutrinoless double {beta} decay (0{nu}{beta}{beta}) measurements on the coupling of the heavy composite neutrinos to the gauge bosons. For neutrino masses {ital M}{sub {ital N}}=1 TeV we obtain a rather weak lower bound on the compositeness scale: {

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}〉.

title: Resonance structures through time-dependent potentials.
abstract: Electron-positron pair production in time-dependent potentials is considered. We find that the particle production distribution probability shows interesting resonance structures. Some numerical applications to heavy ion collisions are made.

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: 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.