401 research outputs found
Prompt Beta Spectroscopy as a Diagnostic for Mix in Ignited NIF Capsules
The National Ignition Facility (NIF) technology is designed to drive
deuterium-tritium (DT) internal confinement fusion (ICF) targets to ignition
using indirect radiation from laser beam energy captured in a hohlraum.
Hydrodynamical instabilities at interfaces in the ICF capsule leading to mix
between the DT fue l and the ablator shell material are of fundamental physical
interest and can affect the performance characteristics of the capsule. In this
Letter we describe new radiochemical diagnostics for mix processes in ICF
capsules with plastic or Be (0.9%Cu) ablator shells. Reactions of high-energy
tritons with shell material produce high-energy -emitters.
We show that mix between the DT fuel and the shell material enhances
high-energy prompt beta emission from these reactions by more than an order of
magnitude over that expected in the absence of mix
Analysis of the chargino and neutralino mass parameters at one-loop level
In the Minimal Supersymmetric Standard Model (MSSM) the masses of the
neutralinos and charginos depend on the gaugino and higgsino mass parameters M,
M' and . If supersymmetry is realized, the extraction of these parameters
from future high energy experiments will be crucial to test the underlying
theory. We present a consistent method how on-shell parameters can be properly
defined at one-loop level and how they can be determined from precision
measurements. In addition, we show how a GUT relation for the parameters M and
M' can be tested at one-loop level. The numerical analysis is based on a
complete one-loop calculation. The derived analytic formulae are given in the
appendix.Comment: 16 pages, 8 figure
The isolation of gravitational instantons: Flat tori V flat R^4
The role of topology in the perturbative solution of the Euclidean Einstein
equations about flat instantons is examined.Comment: 15 pages, ICN-UNAM 94-1
Detecting an Invisibly Decaying Higgs Boson at a Hadron Supercollider
We demonstrate that an invisibly decaying Higgs boson with Standard Model
coupling strength to top--anti-top can be detected at the LHC for masses up to
about 250 GeV.Comment: 7 pages, requires phyzzx.tex and tables.tex, revised to convert
results from SSC to LHC and include additional top quark mass cases, full
postscript file including embedded figure available via anonymous ftp at
ucdhep.ucdavis.edu as [anonymous.gunion]hinvisible_revised.ps, preprint
UCD-93-2
Kinetic decoupling of neutralino dark matter
After neutralinos cease annihilating in the early Universe, they may still
scatter elastically from other particles in the primordial plasma. At some
point in time, however, they will eventually stop scattering. We calculate the
cross sections for neutralino elastic scattering from standard-model particles
to determine the time at which this kinetic decoupling occurs. We show that
kinetic decoupling occurs above a temperature MeV. Thereafter,
neutralinos act as collisionless cold dark matter.Comment: Replaced with revised version, new references adde
Power Spectrum Estimators For Large CMB Datasets
Forthcoming high-resolution observations of the Cosmic Microwave Background
(CMB) radiation will generate datasets many orders of magnitude larger than
have been obtained to date. The size and complexity of such datasets presents a
very serious challenge to analysing them with existing or anticipated
computers. Here we present an investigation of the currently favored algorithm
for obtaining the power spectrum from a sky-temperature map --- the quadratic
estimator. We show that, whilst improving on direct evaluation of the
likelihood function, current implementations still inherently scale as the
equivalent of the cube of the number of pixels or worse, and demonstrate the
critical importance of choosing the right implementation for a particular
dataset.Comment: 8 pages LATEX, no figures, corrected misaligned columns in table
Low energy conversion electron detection in superfluid He3 at ultra-low temperature
We report on the first results of the MACHe3 (MAtrix of Cells of Helium 3)
prototype experiment concerning the measurement of low energy conversion
electrons at ultra-low temperature. For the first time, the feasibility of the
detection of low energy electrons is demonstrated in superfluid He3-B cooled
down to 100 microK. Low energy electrons at 7.3 keV coming from the K shell
conversion of the 14.4 keV nuclear transition of a low activity Co57 source are
detected, opening the possibility to use a He3-based detector for the detection
of Weakly Interacting Massive Particles (WIMPs) which are expected to release
an amount of energy higher-bounded by 5.6 keV.Comment: 8 pages, 3 figures, to appear in NIM
Cosmological measurement of neutrino mass in the presence of leptonic asymmetry
We show that even the smallest neutrino mass consistent with the
Super--Kamiokande data is relevant for cosmological models of structure
formation and cosmic microwave background (CMB) anisotropies, provided that a
relic neutrino asymmetry exists. We calculate the precision with which a 0.07
eV neutrino mass could be extracted from CMB anisotropy and large-scale
structure data by the future Planck satellite and Sloan Digital Sky Survey. We
find that such a mass can be detected, assuming a large relic neutrino
asymmetry still allowed by current experimental data. This measurement of the
absolute value of the neutrino mass would be crucial for our understanding of
neutrino models.Comment: 8 pages, 2 PS figures, version to be publishe
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