2,526 research outputs found
Mass generation and the dynamical role of the Katoptron Group
Heavy mirror fermions along with a new strong gauge interaction capable of
breaking the electroweak gauge symmetry dynamically were recently introduced
under the name of katoptrons. Their main function is to provide a viable
alternative to the Standard-Model Higgs sector. In such a framework, ordinary
fermions acquire masses after the breaking of the strong katoptron group which
allows mixing with their katoptron partners. The purpose of this paper is to
study the elementary-scalars-free mechanism responsible for this breaking and
its implications for the fermion mass hierarchies.Comment: 15 LaTeX pages, some comments added, version published in Modern
Physics Letters
A GaAs-based self-aligned stripe distributed feedback laser
We demonstrate operation of a GaAs-based self-aligned stripe (SAS) distributed feedback (DFB) laser. In this structure, a first order GaInP/GaAs index-coupled DFB grating is built within the p-doped AlGaAs layer between the active region and the n-doped GaInP opto-electronic confinement layer of a SAS laser structure. In this process no Al-containing layers are exposed to atmosphere prior to overgrowth. The use of AlGaAs cladding affords the luxury of full flexibility in upper cladding design, which proved necessary due to limitations imposed by the grating infill and overgrowth with the GaInP current block layer. Resultant devices exhibit single-mode lasing with high side-mode-suppression of >40 dB over the temperature range 20 °C–70 °C. The experimentally determined optical profile and grating confinement correlate well with those simulated using Fimmwave
Integrated Flywheel Technology, 1983
Topics of discussion included: technology assessment of the integrated flywheel systems, potential of system concepts, identification of critical areas needing development and, to scope and define an appropriate program for coordinated activity
Beyond the soft photon approximation in radiative production and decay of charged vector mesons
We study the effects of model-dependent contributions and the electric
quadrupole moment of vector mesons in the decays and
. Their interference with the amplitude originating
from the radiation due to electric charges vanishes for photons emitted
collinearly to the charged particle in the final state. This brings further
support to our claim in previous works, that measurements of the photon energy
spectrum for nearly collinear photons in those decays are suitable for a first
measurement of the magnetic dipole moment of charged vector mesons.Comment: 13 pages, 2 eps figures, Latex. Accepted for publication in Journal
of Physics G: Nuclear and Particle Physics(2001
A Preliminary Indication of Evolution of Type Ia Supernovae from their Risetimes
We have compared the risetime for samples of nearby and high-redshift type Ia
supernovae (SNe Ia).
The fiducial risetime of the nearby SNe Ia is 2.5+/-0.4 days longer than the
proemial risetime determined by Goldhaber (1998a,b) for high-redshift SNe
Ia from the Supernova Cosmology Project.
The statistical likelihood that the two samples have different fiducial
risetimes is high (5.8 sigma) and indicates possible evolution between the
samples of SNe Ia. We consider the likely effects of several sources of
systematic error, but none of these resolves the difference in the risetimes.
Currently, we cannot directly determine the impact of the apparent evolution
on previous determinations of cosmological parameters.Comment: Accepted by the Astronomical Journal, 11 pages, 5 figure
Light bottom squark and gluino confront electroweak precision measurements
We address the compatibility of a light sbottom (mass 2\sim 5.5 \gev) and a
light gluino (mass 12\sim 16 \gev) with electroweak precision measurements.
Such light particles have been suggested to explain the observed excess in the
quark production cross section at the Tevatron. The electroweak observables
may be affected by the sbottom and gluino through the SUSY-QCD corrections to
the vertex. We examine, in addition to the SUSY-QCD corrections, the
electroweak corrections to the gauge boson propagators from the stop which are
allowed to be light from the SU(2) symmetry. We find that this scenario is
strongly disfavored from electroweak precision measurements unless the heavier
sbottom mass eigenstate is lighter than 180\gev and the left-right mixing in
the stop sector is sufficiently large. This implies that one of the stops
should be lighter than about 98\gev.Comment: 4 pages, revtex, 2 figures. Reference added, version to appear in
Phys.Rev.Let
The Probability Density of the Higgs Boson Mass
The LEP Collaborations have reported a small excess of events in their
combined Higgs boson analysis at center of mass energies up to about 208 GeV.
In this communication, I present the result of a calculation of the probability
distribution function of the Higgs boson mass which can be rigorously obtained
if the validity of the Standard Model is assumed. It arises from the
combination of the most recent set of precision electroweak data and the
current results of the Higgs searches at LEP 2.Comment: 3 pages, 2 figure
Diversity of Decline-Rate-Corrected Type Ia Supernova Rise Times: One Mode or Two?
B-band light-curve rise times for eight unusually well-observed nearby Type
Ia supernovae (SNe) are fitted by a newly developed template-building
algorithm, using light-curve functions that are smooth, flexible, and free of
potential bias from externally derived templates and other prior assumptions.
From the available literature, photometric BVRI data collected over many
months, including the earliest points, are reconciled, combined, and fitted to
a unique time of explosion for each SN. On average, after they are corrected
for light-curve decline rate, three SNe rise in 18.81 +- 0.36 days, while five
SNe rise in 16.64 +- 0.21 days. If all eight SNe are sampled from a single
parent population (a hypothesis not favored by statistical tests), the rms
intrinsic scatter of the decline-rate-corrected SN rise time is 0.96 +0.52
-0.25 days -- a first measurement of this dispersion. The corresponding global
mean rise time is 17.44 +- 0.39 days, where the uncertainty is dominated by
intrinsic variance. This value is ~2 days shorter than two published averages
that nominally are twice as precise, though also based on small samples. When
comparing high-z to low-z SN luminosities for determining cosmological
parameters, bias can be introduced by use of a light-curve template with an
unrealistic rise time. If the period over which light curves are sampled
depends on z in a manner typical of current search and measurement strategies,
a two-day discrepancy in template rise time can bias the luminosity comparison
by ~0.03 magnitudes.Comment: As accepted by The Astrophysical Journal; 15 pages, 6 figures, 2
tables. Explanatory material rearranged and enhanced; Fig. 4 reformatte
Yet another way to measure
We show that the CKM phase can be extracted from measurement
of the time dependent rates in the decays and
, where , , , , ,
. These channels have a large asymmetry between decays of
and into the same final state. Even though the branching ratios are
small, their sensitivity to can be competitive with decays into
and .Comment: 5 pages, some clarifications and references adde
On the possibility to search for double beta decay of initially unstable (alpha/beta radioactive) nuclei
Possibilities to search for double beta decay of alpha/beta unstable nuclei,
many of which have higher energy release than "conventional" (beta stable)
double beta decay candidates, are discussed. First experimental half-life
limits on double beta decay of radioactive nuclides from U and Th families
(trace contaminants of the CaWO_4, CdWO_4 and Gd_2SiO_5 scintillators) were
established by reanalyzing the data of low-background measurements in the
Solotvina Underground Laboratory with these detectors (1734 h with CaWO_4,
13316 h with CdWO_4, and 13949 h with Gd_2SiO_5 crystals).Comment: 15 pages, 6 figure
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