21 research outputs found
Self-consistent antikaon dynamics in isospin-asymmetric nuclear medium
We investigate properties of antikaons and hyperon resonances in
isospin-asymmetric nuclear medium, using a self-consistent, covariant scheme
based on vacuum antikaon-nucleon scattering amplitude.Comment: 9 pages, 5 figures, uses budapest.sty (included);to be published in
the Proceedings of the Budapest'2002 Workshop on Quark and Hadron Dynamics,
Budapest, Hungary, 3-7 March 200
Kaon and antikaon properties in cold nuclear medium
We present results of a self-consistent calculation for the kaon and antikaon
spectral functions in cold nuclear matter, using as input the kaon-nucleon and
antikaon-nucleon scattering amplitudes of the vacuum. We investigate the effect
of in-medium pion dressing on the antikaon-nucleon scattering amplitudes and
antikaon spectral function. We find the influence of pion dressing to be minor
on the antikaon spectral function and limited on the hyperon resonances causing
only a small additional broadening. An exception is the \Sigma(1690). At
nuclear saturation density an attractive mass shift of about 20 MeV and width
of about 130 MeV is obtained. The kaon shows a repulsive mass increase of 36
MeV and a small width of the quasiparticle peak at saturation density.Comment: 8 pages, 4 figures, submitted to Heavy Ion Physic
Chiral symmetry, strangeness and resonances
We review the important role played by the chiral SU(3) symmetry in
predicting the properties of antikaons and hyperon resonances in cold nuclear
matter. Objects of crucial importance are the meson-baryon scattering
amplitudes obtained within the chiral coupled-channel effective field theory.
The formation of baryon resonances as implied by chiral coupled-channel
dynamics is discussed. Results for antikaon and hyperon-resonance spectral
functions are presented for isospin symmetric and asymmetric matter.Comment: invited talk presented by M.F.M.L. at the 18th Nishinomiya Yukawa
Memorial Symposium, 21 pages, 12 figure
Chiral SU(3) Symmetry and Strangeness
In this talk we review recent progress on the systematic evaluation of the
kaon and antikaon spectral functions in dense nuclear matter based on a chiral
SU(3) description of the low-energy pion-, kaon- and antikaon-nucleon
scattering data.Comment: 9 pages, 4 figures, invited talk given by M.F.M.L. at the SQM2001
conferenc
Resonance production in heavy ion collisions
Recent results of resonance production from RHIC at
200 GeV and SPS at 17 GeV are presented and discussed in
terms of the evolution and freeze-out conditions of a hot and dense fireball
medium. Yields and spectra are compared with thermal model predictions at
chemical freeze-out. Deviations in the low transverse momentum region of the
resonance spectrum of the hadronic decay channel, suggest a strongly
interaction hadronic phase between chemical and kinetic freeze-out. Microscopic
models including resonance rescattering and regeneration are able to describe
the trend of the data. The magnitude of the regeneration cross sections for
different inverse decay channels are discussed. Model calculations which
include elastic hadronic interactions between chemical freeze-out and thermal
freeze-out based on the K(892)/K and (1520)/ ratios suggest a
time between two freeze-outs surfaces of 4 fm/c. The difference
in momentum distributions and yields for the (1020) resonance
reconstructed from the leptonic and hadronic decay channels at SPS energy are
discussed taking into account the impact of a hadronic phase and possible
medium modifications.Comment: 8 pages, 4 figures, conference proceedings (SQM2004
What do we learn from Resonance Production in Heavy Ion Collisions?
Resonances with their short life time and strong coupling to the dense and
hot medium are suggested as a signature of the early stage of the fireball
created in a heavy ion collision \cite{rap00,lut01,lut02}. The comparison of
resonances with different lifetimes and quark contents may give information
about time evolution and density and temperature of during the expanding of
fireball medium. Resonances in elementary reactions have been measured since
1960. Resonance production in elementary collisions compared with heavy ion
collisions where we expect to create a hot and dense medium may show the direct
of influence of the medium on the resonances. This paper shows a selection of
the recent resonance measurements from SPS and RHIC heavy ion colliders.Comment: 10 pages, 8 figures, HotQuarks 2004 conference proceeding
Dynamics and freeze-out of hadron resonances at RHIC
Yields, rapidity and transverse momentum spectra of ,
, and the meson resonances ,
, and are predicted. Hadronic rescattering leads to a
suppression of reconstructable resonances, especially at low . A mass
shift of the of 10 MeV is obtained from the microscopic simulation, due
to late stage formation in the cooling pion gas.Comment: Proceedings of the Strange Quark Matter 2003, eprint version differs
from published versio
A quark model framework for the study of nuclear medium effects
A quark-model framework for studying nuclear medium effects on nucleon
resonances is described and applied here to pion photoproduction on the
deuteron, which is the simplest composite nucleon system and serves as a first
test case. Pion photoproduction on nuclei is discussed within a chiral
constituent quark model in which the quark degrees of freedom are explicitly
introduced through an effective chiral Lagrangian for the
quark-pseudoscalar-meson coupling. The advantage of this model is that a
complete set of nucleon resonances can be systematically included with a
limited number of parameters. Also, the systematic description of the nucleon
and its resonances at quark level allows us to self-consistently relate the
nuclear medium's influence on the baryon properties to the intrinsic dynamic
aspects of the baryons. As the simplest composite nucleus, the deuteron
represents the first application of this effective theory for meson
photoproduction on light nuclei. The influence of the medium on the transition
operators for a free nucleon is investigated in the Delta resonance region. No
evidence is found for a change of the Delta properties in the pion
photoproduction reaction on the deuteron since the nuclear medium here involves
just one other nucleon and the low binding energy implies low nuclear density.
However, we show that the reaction mechanism is in principle sensitive to
changes of Delta properties that would be produced by the denser nuclear medium
of heavier nuclei through the modification of the quark model parameters.Comment: Revtex, 8 pages, 4 figure
QCD and strongly coupled gauge theories : challenges and perspectives
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe