753 research outputs found
Radiative Production of Non-thermal Dark Matter
We compare dark matter production from the thermal bath in the early universe
with its direct production through the decay of the inflaton. We show that even
if dark matter does not possess a direct coupling with the inflaton, Standard
Model loop processes may be sufficient to generate the correct relic abundance.Comment: 12 pages, 8 figure
Event anisotropy of identified , photon and electron compared to charged , , and deuteron in = 200 GeV Au+Au at PHENIX
We report the recent results of event anisotropy analysis focused on in
= 200 GeV Au+Au collisions at PHENIX.Comment: 4 pages, 3 figures, contribution to the proceedings of the 17th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter, Oakland, January 11-17, 2004). To appear in the proceedings
(Journal of Physics G
Quantifying Limits on CP Violating Phases from EDMs in Supersymmetry
We revisit the calculation of the electron, neutron, and proton electric
dipole moments (EDMs) in the constrained minimal supersymmetric standard model
(CMSSM). The relatively large mass of the Higgs boson, GeV
coupled with the (as yet) lack of discovery of any supersymmetric particle at
the LHC, has pushed the supersymmetry breaking scale to several TeV or higher.
Though one might expect this decoupling to have relaxed completely any bounds
on the two CP violating phases in the CMSSM ( and ), the
impressive experimental improvements in the limits on the EDMs (particularly
the electron EDM) still allow us to set constraints of order
on and on . We also discuss the
impact of future improvements in the experimental limits on supersymmetric
models.Comment: 34 pages, 8 figure
The Role of Vectors in Reheating
We explore various aspects concerning the role of vector bosons during the
reheating process. Generally, reheating occurs during the period of
oscillations of the inflaton condensate and the evolution of the radiation bath
depends on the inflaton equation of state. For oscillations about a quadratic
minimum, the equation of state parameter, , and the evolution of
the temperature, with respect to the scale factor is independent of the
spin of the inflaton decay products. However, for cases when , there is a
dependence on the spin, and here we consider the evolution when the inflaton
decays or scatters to vector bosons. We also investigate the gravitational
production of vector bosons as potential dark matter candidates. Gravitational
production predominantly occurs through the longitudinal mode. We compare these
results to the gravitational production of scalars.Comment: 37 pages, 9 Figure
Centrality Dependence of Thermal Parameters Deduced from Hadron Multiplicities in Au + Au Collisions at sqrt{s_{NN}} = 130 GeV
We analyse the centrality dependence of thermal parameters deduced from
hadron m ultiplicities in Au + Au collisions at .
While the chemical freeze-out temperature and chemical potentials are found to
be roughly centrality-independent, the strangeness saturation factor
increases with participant number towards unity, supporting the assumption of
equilibrium freeze-out conditions in central collisions
A Start-Timing Detector for the Collider Experiment PHENIX at RHIC-BNL
We describe a start-timing detector for the PHENIX experiment at the
relativistic heavy-ion collider RHIC. The role of the detector is to detect a
nuclear collision, provide precise time information with an accuracy of 50ps,
and determine the collision point along the beam direction with a resolution of
a few cm. Technical challenges are that the detector must be operational in a
wide particle-multiplicity range in a high radiation environment and a strong
magnetic field. We present the performance of the prototype and discuss the
final design of the detector.Comment: 12 pages, LaTeX, 9 gif and 4 ps figures. Submitted to NIM
Change of Electronic Structure Induced by Magnetic Transitions in CeBi
The temperature dependence of the electronic structure of CeBi arising from
two types of antiferromagnetic transitions based on optical conductivity
() was observed. The spectrum continuously and
discontinuously changes at 25 and 11 K, respectively. Between these
temperatures, two peaks in the spectrum rapidly shift to the opposite energy
sides as the temperature changes. Through a comparison with the band
calculation as well as with the theoretical spectrum, this
peak shift was explained by the energy shift of the Bi band due to the
mixing effect between the Ce and Bi states. The single-layer
antiferromagnetic () transition from the paramagnetic state was concluded
to be of the second order. The marked changes in the spectrum
at 11 K, however, indicated the change in the electronic structure was due to a
first-order-like magnetic transition from a single-layer to a double-layer
() antiferromagnetic phase.Comment: 4 pages, to be published in J. Phys. Soc. Jpn. 73 Aug. (2004
Geometry and quantum delocalization of interstitial oxygen in silicon
The problem of the geometry of interstitial oxygen in silicon is settled by
proper consideration of the quantum delocalization of the oxygen atom around
the bond-center position. The calculated infrared absorption spectrum accounts
for the 517 and 1136 cm bands in their position, character, and isotope
shifts. The asymmetric lineshape of the 517 cm peak is also well
reproduced. A new, non-infrared-active, symmetric-stretching mode is found at
596 cm. First-principles calculations are presented supporting the
nontrivial quantum delocalization of the oxygen atom.Comment: uuencoded, compressed postscript file for the whole. 4 pages (figures
included), accepted in PR
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