87 research outputs found
Dilepton Production in Nucleon-Nucleon Reactions With and Without Hadronic Inelasticities
We calculate elementary proton-proton and neutron-proton bremsstrahlung and
their contribution to the invariant mass distribution. At 4.9 GeV, the
proton-proton contribution is larger than neutron-proton, but it is small
compared to recent data. We then make a first calculation of bremsstrahlung in
nucleon-nucleon reactions with multi-hadron final states. Again at 4.9 GeV, the
many-body bremsstrahlung is larger than simple nucleon-nucleon bremsstrahlung
by more than an order of magnitude in the low-mass region. When the
bremsstrahlung contributions are summed with Dalitz decay of the ,
radiative decay of the and from two-pion annihilation, the result
matches recent high statistics proton-proton data from the Dilepton
Spectrometer collaboration.Comment: 1+17 pages plus 11 PostScript figures uuencoded and appended,
McGill/93-9, TPI-MINN-93/18-
Rate of photon production from hot hadronic matter
Thermal photon emission rates from hot hadronic matter are studied to order
, where indicates a strong-interaction coupling constant.
Radiative decay of mesons, Compton and annihilation processes for hadrons, and
bremsstrahlung reactions are all considered. Compared to the standard rates
from the literature, one finds two orders of magnitude increase for low photon
energies stemming mainly from bremsstrahlung and then a modest increase (factor
of 2) for intermediate and high energy photons owing to radiative decays for a
variety of mesons and from other reactions involving strangeness. These results
could have important consequences for electromagnetic radiation studies at
RHIC.Comment: 5 pages LaTeX, 4 Postscript figure
Collision broadening of rho meson in a dropping mass scenario
Vector mesons containing light quarks are thought to have their masses
reduced in dense nuclear matter, sacrificing some of their energy to the scalar
field which becomes appreciable at finite baryon density. Model calculations
find masses which fall by a couple tens of percents in normal nuclear matter,
and by several hundred MeV in dense matter. We estimate the collision rate for
rho mesons in such a scenario and at finite temperature. Compared to its
free-mass value, the collision rate changes by nearly a factor of two both
above and below, depending on the density. This collision broadening effect
could be important for estimates of low-mass dilepton production in heavy-ion
collisions.Comment: 8 pages LaTeX, 2 PostScript figure
Excess electron pairs from heavy-ion collisions at CERN and a more complete picture of thermal production
The low-mass dielectron signal from heavy-ion collisions at the CERN--SPS
reported by the {\em CERES} collaboration is in excess of estimated hadronic
decays suggestive of possible contribution from two-pion annihilation or other
hadronic reactions. In the absence of dramatic medium modifications,
annihilation alone is unable to account for the data. We explore the role of
pion plus resonance scattering [] which
has favorable kinematics to populate masses between and .
While it seems to account for some of the remaining excess beyond annihilation,
it fails to allow quantitative interpretation of data.Comment: 11 pages LaTeX, 3 PostScript figure
-kaon cross section in meson exchange model
We calculate the cross section for the dissociation of by kaons
within the framework of a meson exchange model including anomalous parity
interactions. Off-shell effects at the vertices were handled with QCD sum rule
estimates for the running coupling constants. The total -kaon cross
section was found to be mb for 4.1\leq\sqrt{s}\leq5 \GeV.Comment: 13 pages, 4 eps figure
Photons from axial-vector radiative decay in a hadron gas
Strange and non-strange axial-vector meson radiative decays contribute to
photon production in hadron gas. One- and two-hadron radiative decay modes of
, and are studied. At 200 MeV
temperature and for a narrow range in photon energies they contribute more to
the net thermal photon production rate than ,
or . They provide
significant contribution to the rate for photon energies as high as 1.5--2.0
GeV. For higher energies they are less important.Comment: 10 pages + 7 figures uuencoded in separate file, MSUCL-92
J/Psi Propagation in Hadronic Matter
We study J/ propagation in hot hadronic matter using a four-flavor
chiral Lagrangian to model the dynamics and using QCD sum rules to model the
finite size effects manifested in vertex interactions through form factors.
Charmonium breakup due to scattering with light mesons is the primary
impediment to continued propagation. Breakup rates introduce nontrivial
temperature and momentum dependence into the J/ spectral function.Comment: 6 Pages LaTeX, 3 postscript figures. Proceedings for Strangeness in
Quark Matter 2003, Atlantic Beach, NC, March 12-17, 2003; minor corrections
in version 2, to appear in J. Phys.
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