726 research outputs found
Meson Properties in Dense Hadronic Matter
The medium modification of mesons in dense hadronic matter is discussed with
a focus on the relationship to the chiral structure of the non-perturbative QCD
vacuum.Comment: Proc. Third Int. Conf. on "Perspectives in Nuclear Physics", Trieste
2001 8pages+5figure
Chiral Symmetry Restoration and Dileptons in Relativistic Heavy-Ion Collisions
The current theoretical status in the analysis and interpretation of low-mass
dilepton measurements in (ultra-) relativistic heavy-ion experiments is
reviewed. Special emphasis is put on potential signals of (partial) restoration
of dynamically broken chiral symmetry in a hot and dense hadronic medium. It
follows from chiral symmetry alone that parity partners of hadronic correlation
functions must become identical when the symmetry is restored. The assessment
of medium effects in the vector channel, which governs the dilepton production,
thus necessitates a simultaneous treatment of the vector and axialvector
degrees of freedom. While significant progress in this respect has been made
some open questions remain in establishing a rigorous link in the mass region
below 1 GeV. From the present calculations a suggestive 'quark-hadron duality'
emerges near the phase boundary. It implies substantial medium effects in the
dilepton signal from the hadronic phase which smoothly matches a perturbative
description within the plasma phase.Comment: 164 pages LaTeX including 88 eps-/ps-figures, Review Article to
appear in Adv. Nucl. Phy
Probing Chiral Symmetry Restoration with Heavy Ions
It is discussed how chiral symmetry restoration manifests itself through
mixing of vector and axial-vector correlators. The vector correlator is
directly accessible in relativistic heavy-ion collisions. Within models of the
vector correlator its implications for low-mass dilepton spectra are reviewed.Comment: 11 pages LaTeX, incl. 6 eps-figures and appb.sty; Talk given at the
Workshop on 'The Structure of Mesons, Baryons and Nuclei', Cracow, May 1998,
in honor of J. Speth's 60th birthday, to be published in Acta Physica
Polonica
Finite-Temperature Gluon Condensate with Renormalization Group Flow Equations
Within a self-consistent proper-time Renormalization Group (RG) approach we
investigate an effective QCD trace anomaly realization with dilatons and
determine the finite-temperature behavior of the gluon condensate. Fixing the
effective model at vanishing temperature to the glueball mass and the bag
constant a possible gluonic phase transition is explored in detail. Within the
RG framework the full non-truncated dilaton potential analysis is compared with
a truncated potential version.Comment: 22 pages, 11 figures, LaTeX2e; revised version accepted for
publication in Phys. Rev.
The Linear Sigma-Model in the 1/N-Expansion via Dynamical Boson Mappings and Applications to -Scattering
We present a non-perturbative method for the study of the O(N+1)-version of
the linear sigma-model. Using boson-mapping techniques, in close analogy to
those well-known for fermionic systems, we obtain a systematic 1/N-expansion
for the Hamiltonian which is symmetry-conserving order by order. The leading
order for the Hamiltonian is evaluated explicitly and we apply the method to
-scattering, in deriving the T-matrix to leading order.Comment: 28 pages, Latex, (with minor corrections to some misprints in the
appendix of the old version
The quark condensate at finite temperature
The temperature evolution of the quark condensate is studied using three
different methods. In the spirit of a many-body approach we make an expansion
in the scalar density up to second order. Our result is consistent chiral
perturbation theory to two-loop order.Comment: Latex 14 pages + 1 figure (postscript
Transport Properties of Strong-Interaction Matter
The properties of strong-interaction matter are probed in ultra-relativistic
heavy-ion collisions. In the context of measurements of the elliptic flow at
RHIC and the LHC the shear viscosity is of particular interest. In this
presentation we discuss recent results for eta/s in hadronic matter at
vanishing baryo-chemical potential within kinetic theory. Using the
Nambu-Jona-Lasinio model, special attention is paid to effects arising from the
restoration of spontaneously broken chiral symmetry with increasing
temperature.Comment: 8 pages, 4 figures, presented at the HIC for FAIR Workshop and XXVIII
Max Born Symposium "Three days on Quarkyonic Island", Wroclaw, May 19-21,
2011; v2: conversion to Pa in fig. 2 correcte
Rho Meson Propagation and Dilepton Enhancement in Hot Hadronic Matter
A realistic model for the free rho meson with coupling to two-pion states is
employed to calculate the rho propagator in a hot and dense hadron gas. The
medium modifications are based on hadronic rescattering processes: intermediate
two-pion states are renormalized through interactions with surrounding nucleons
and deltas, and rho meson scattering is considered off nucleons, deltas, pions
and kaons. Constraints from gauge invariance as well as the full off-shell
dynamics of the interactions are accounted for. Within the vector dominance
model we apply the resulting in-medium rho spectral function to compute
production rates from annihilation. The calculation of
corresponding spectra as recently measured in central collisions of
heavy-ions at CERN/SpS energies gives reasonable agreement with the
experimental data.Comment: 27 pages RevTeX, 9 eps-figures, submitted to Nucl. Phys.
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