42 research outputs found
Meson Mixing and Dilepton Production in Heavy Ion Collisions
We study the possibility of mixing via N-N excitations in dense
nuclear matter. This mixing is found to induce a peak in the dilepton spectra
at an invariant mass equal to that of the . We calculate the cross section
for dilepton production through mixing and we compare its size with that of
annihilation. In-medium masses and mixing angles are also calculated.
Some preliminary results of the mixing effect on the dilepton production rates
at finite temperature are also presented.Comment: To be published in the proceedings of CIPANP 200
Squeezing lepton pairs out of broken symmetries
We discuss two possible signatures of symmetry breaking that can appear in
dilepton spectra, as measured in relativistic heavy ion collisions. The first
involves scalar-vector meson mixing and is related to the breaking of Lorentz
symmetry by a hot medium. The second is related to the breaking of Furry's
theorem by a charged quark-gluon plasma. Those signals will be accessible to
upcoming measurements to be performed at the GSI, RHIC, and the LHC.Comment: 5 pages, 4 figures, talk given at the INPC 2001 (International
Conference on Nuclear Physics), 30 July - 3 August 2001, Berkeley, C
Isospin mode splitting and mixing in asymmetric nuclear matter
We estimate exclusive density and asymmetry parameter dependent dispersion
relations of various charged states of pions in asymmetric nuclear matter. The
possibility of matter induced mixing of with is clearly exposed
with the further mass modification of meson due to mixing. Asymmetry
driven mass splitting and mixing amplitude are of the same order as the
corresponding values in vacuum. Closed form analytic results for the mass
shifts and dispersion relations with and without mixing are presented.
Furthermore, we discuss the sensitivity of our results on the scalar mean field
within the framework of Quantum Hadrodynamics.Comment: 8 pages, 4 Figure
Baryonic contributions to the dilepton spectra in relativistic heavy ion collisions
We investigate the baryonic contributions to the dilepton yield in high
energy heavy ion collisions within the context of a transport model. The
relative contribution of the baryonic and mesonic sources are examined. It is
observed that most dominant among the baryonic channels is the decay of
N*(1520) and mostly confined in the region below the rho peak. In a transport
theory implementation we find the baryonic contribution to the lepton pair
yield to be small.Comment: 11 pages, 8 figure
Rho-omega mixing in asymmetric nuclear matter via QCD sum rule approach
We evaluate the operator product expansion (OPE) for a mixed correlator of
the isovector and isoscalar vector currents in the background of the nucleon
density with intrinsic isospin asymmetry [i.e. excess of neutrons over protons]
and match it with its imaginary part, given by resonances and continuum, via
the dispersion relation. The leading density-dependent contribution to
mixing is due the scattering term, which turns out to be larger
than any density dependent piece in the OPE. We estimate that the asymmetric
density of induces the amplitude
of mixing, equal in magnitude to the mixing amplitude in vacuum,
with the constructive interference for positive and destructive for negative
values of . We revisit sum rules for vector meson masses at finite
nucleon density to point out the numerical importance of the screening term in
the isoscalar channel, which turns out to be one order of magnitude larger than
any density-dependent condensates over the Borel window. This changes the
conclusions about the density dependence of , indicating
MeV increase at nuclear saturation density.Comment: 8 pages, Revte
- mixing and spin dependent CSV potential
We construct the charge symmetry violating (CSV) nucleon-nucleon potential
induced by the -\o mixing due to the neutron-proton mass difference
driven by the loop. Analytical expression for for the two-body CSV
potential is presented containing both the central and non- central
interaction. We show that the tensor interaction can significantly
enhance the charge symmetry violating interaction even if momentum
dependent off-shell - mixing amplitude is considered. It is
also shown that the inclusion of form factors removes the divergence arising
out of the contact interaction. Consequently, we see that the precise size of
the computed scattering length difference depends on how the short range
aspects of the CSV potential are treated.Comment: Accepted for publication in Phys. Rev.
Thermal Radiation from Au + Au Collisions at \sqrt{s} = 200 GEV/A Energy
The transverse momentum distribution of the direct photons measured by the
PHENIX collaboration in collisions at GeV/A has been
analyzed. It has been shown that the data can be reproduced reasonably well
assuming a deconfined state of thermalized quarks and gluons with initial
temperature more than the transition temperature for deconfinement inferred
from lattice QCD. The value of the initial temperature depends on the equation
of state of the evolving matter. The sensitivities of the results on various
input parameters have been studied. The effects of the modifications of
hadronic properties at non-zero temperature have been discussed.Comment: minor modifications in the text, accepted for publicatio