990 research outputs found
Relativistic Expansion of Electron-Positron-Photon Plasma Droplets and Photon Emission
The expansion dynamics of hot electron-positron-photon plasma droplets is
dealt with within relativistic hydrodynamics. Such droplets, envisaged to be
created in future experiments by irradiating thin foils with
counter-propagating ultra-intense laser beams, are sources of flashes of gamma
radiation. Warm electron-positron plasma droplets may be identified and
characterized by a broadened 511 keV line
Thermodynamics of the \phi^4 theory in tadpole approximation
Relying on the Luttinger-Ward theorem we derive a thermodynamically
selfconsistent and scale independent approximation of the thermodynamic
potential for the scalar theory in the tadpole approximation. The
resulting thermodynamic potential as a function of the temperature is similar
to the one of the recently proposed screened perturbation theory.Comment: 6 pages, including 1 eps figur
A unique parametrization of the shapes of secondary dilepton spectra observed in central heavy-ion collisions at CERN-SPS energies
A unique parametrization of secondary (thermal) dilepton yields in heavy-ion
experiments at CERN-SPS is proposed. This parametrization resembles a thermal
annihilation rate. This is inspired by the observation that lepton
pair production rates are quantitatively similar, whether expressed in a
hadronic or partonic basis. Adding the thermal yield and the background
contributions (hadronic cocktail, Drell-Yan, correlated semileptonic decays of
open charm) the spectral shapes of the CERES/NA45, NA38, NA50 and HELIOS/3 data
from experiments with lead and sulfur beams can be well described.Comment: 23 pages including figures (new version: only new output format
Systematic Effective Field Theory Investigation of Spiral Phases in Hole-Doped Antiferromagnets on the Honeycomb Lattice
Motivated by possible applications to the antiferromagnetic precursor of the
high-temperature superconductor NaCoOyHO, we use a systematic
low-energy effective field theory for magnons and holes to study different
phases of doped antiferromagnets on the honeycomb lattice. The effective action
contains a leading single-derivative term, similar to the Shraiman-Siggia term
in the square lattice case, which gives rise to spirals in the staggered
magnetization. Depending on the values of the low-energy parameters, either a
homogeneous phase with four or a spiral phase with two filled hole pockets is
energetically favored. Unlike in the square lattice case, at leading order the
effective action has an accidental continuous spatial rotation symmetry.
Consequently, the spiral may point in any direction and is not necessarily
aligned with a lattice direction.Comment: 10 pages, 6 figure
Role of phi decays for K- yields in relativistic heavy-ion collisions
The production of strange mesons in collisions of Ar+KCl at a kinetic beam
energy of 1.756 AGeV is studied within a transport model of
Boltzmann-\"Uhling-Uhlenbeck (BUU) type. In particular, and
yields and spectra are compared to the data mesured recently by the HADES
collaboration and the yield measured previously by the FOPI
collaboration. Our results are in agreement with these data thus presenting an
interpretation of the subleading role of decays into 's and
confirming the importance of the strangeness-exchange channels for
production.Comment: 24 pages, 19 figure
Evidence for In-Medium Changes of Four-Quark Condensates
Utilizing the QCD sum rule approach to the behavior of the omega meson in
nuclear matter we derive evidence for in-medium changes of particular
four-quark condensates from the recent CB-TAPS experiment for the reaction
gamma + A -> A' + omega (-> pi0 gamma) with A = Nb and LH2.Comment: Submitted to Phys. Rev. Lett., 4 page
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