4,879 research outputs found
LANNDD---A Massive Liquid Argon Detector for Proton Decay, Supernova and Solar Neutrino Studies, and a Neutrino Factory Detector
We describe a possible Liquid Argon Neutrino and Nuclear Decay Detector
(LANNDD) that consists of a 70kt magnetized liquid argon tracking detector. The
detector is being designed for the Carlsbad Underground Laboratory.Comment: 8 pages, 5 figures; for the Neutrino Facory Meeting at KEK-NUFACT '0
A New Source for Electroweak Baryogenesis in the MSSM
One of the most experimentally testable explanations for the origin of the
baryon asymmetry of the universe is that it was created during the electroweak
phase transition, in the minimal supersymmetric standard model. Previous
efforts have focused on the current for the difference of the two Higgsino
fields, , as the source of biasing sphalerons to create the baryon
asymmetry. We point out that the current for the orthogonal linear combination,
, is larger by several orders of magnitude. Although this increases
the efficiency of electroweak baryogenesis, we nevertheless find that large
CP-violating angles are required to get a large enough baryon
asymmetry.Comment: 4 pages, 2 figures; numerical error corrected, which implies that
large CP violation is needed to get observed baryon asymmetry. We improved
solution of diffusion equations, and computed more accurate values for
diffusion coefficient and damping rate
Bounding the dimensions of rational cohomology groups
Let be an algebraically closed field of characteristic , and let
be a simple simply-connected algebraic group over that is defined and
split over the prime field . In this paper we investigate
situations where the dimension of a rational cohomology group for can be
bounded by a constant times the dimension of the coefficient module. We then
demonstrate how our results can be applied to obtain effective bounds on the
first cohomology of the symmetric group. We also show how, for finite Chevalley
groups, our methods permit significant improvements over previous estimates for
the dimensions of second cohomology groups.Comment: 13 page
Status of Electroweak Phase Transition and Baryogenesis
I review recent progress on the electroweak phase transition and
baryogenesis, focusing on the minimal supersymmetric standard model as the
source of new physics.Comment: 10 pp, 6 figures; plenary talk given at 6th Workshop on High Energy
Physics Phenomenology, 4 Jan. 2000, Chennai, India. v.2: added reference
Solar response of the BATSE instrument on the gamma-ray observatory
The Burst and Transient Source Experiment (BATSE) on board the gamma ray observatory (GRO) aims at comprehensive observations of time profiles, spectra, and locations of high-energy transient sources. The mysterious cosmic gamma ray bursts provided the main motivation for the observations, but BATSE will make excellent observations of many classes of sources, and in particular solar flares. The solar response of BATSE, as inferred from its design parameters, is analyzed for two purposes: the optimization of the solar observations themselves, and the characterization of the solar effects on ordinary nonsolar observations
Neutrinos from supernovae: experimental status and perspectives
I discuss the state of the art in the search for neutrinos from galactic
stellar collapses and the future perspectives of this field. The implications
for the neutrino physics of a high statistics supernova neutrino burst
detection by the network of detectors operating around the world are also
reviewed.Comment: 19 pages, 12 figures. Extended version of talk given at IInd
International Workshop on Matter, Anti-Matter and Dark Matter, Trento
(Italy), 29-30 October 2001. A reduced version will appear in Int. J. of Mod.
Phys.
Gamma-ray burst spectroscopy capabilities of the BATSE/GRO experiment
A scintillation spectrometer is included in each of the eight BATSE/GRO detector modules, resulting in all-sky coverage for gamma-ray bursts. The scientific motivation, design and capabilities of these spectrometers for performing spectral observations over a wide range of gamma-ray energies and burst intensities are described
Effect of reheating on electroweak baryogenesis
The latent heat released during the expansion of bubbles in the electroweak
phase transition reheats the plasma and causes the bubble growth to slow down.
This decrease of the bubble wall velocity affects the result of electroweak
baryogenesis. Since the efficiency of baryogenesis peaks for a wall velocity
, the resulting baryon asymmetry can either be enhanced or
suppressed, depending on the initial value of the wall velocity. We calculate
the evolution of the phase transition taking into account the release of latent
heat. We find that, although in the SM the baryon production is enhanced by
this effect, in the MSSM it causes a suppression to the final baryon asymmetry.Comment: 4 pages, 3 figures. References added. Revised version to be published
in Phys.Rev.
Burst and Transient Source Experiment (BATSE) for the Gamma Ray Observatory (GRO)
The Burst and Transient Source Experiment (BATSE) on the Gamma Ray Observatory (GRO) is expected to provide new and better observational data on bursts to test current and future models of burst sources. These data will include: (1) the celestial distribution of hundreds of burst sources over the life of the mission, (2) burst locations within several degrees, within 2 days after their occurrence, (3) observations of weaker bursts and better observations of short timescale fluctuations and spectral variations, (4) observations by a single experiment over a much larger energy range than previously available, and (5) more sensitive measurements of the spectral features which have been observed in many bursts. This paper briefly describes the GRO mission, the BATSE instrumentation and the burst observational capabilities
Detection of a fast, intense and unusual gamma ray transient
An unusual transient pulse of approximately 50 keV was detected by the gamma-ray burst sensor network using nine space probes and satellites. Its characteristics are unlike those of the known variety of gamma-ray bursts and therefore suggest that it was formed either by a completely different origin species or in a very different manner. It is identified with the LMC supernova remnant N49
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