134 research outputs found
Plasma Energy Loss into Kaluza-Klein Modes
Recently, Barger {\em et al.} computed energy losses into Kaluza Klein modes
from astrophysical plasmas in the approximation of zero density for the
plasmas. We extend their work by considering the effects of finite density for
two plasmon processes. Our results show that, for fixed temperature, the energy
loss rate per cm is constant up to some critical density and then falls
exponentially. This is true for transverse and longitudinal plasmons in both
the direct and crossed channels over a wide range of temperature and density. A
difficulty in deriving the appropriate covariant interaction energy at finite
density and temperature is addressed. We find that, for the cases considered by
Barger {\em et al.}, the zero density approximation and the neglect of other
plasmon processes is justified to better than an order of magnitude.Comment: 17 pages, LaTeX2e, 4 figures, 11 table
The Photovoltaic Array Space Power plus Diagnostics (PASP Plus) Flight Experiment
An overview of the Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) flight experiment is presented in outline and graphic form. The goal of the experiment is to test a variety of photovoltaic cell and array technologies under various space environmental conditions. Experiment objectives, flight hardware, experiment control and diagnostic instrumentation, and illuminated thermal vacuum testing are addressed
Extra dimensions and invisible decay of orthopositronium
We point out that some models with infinite additional dimension(s) of
Randall-Sundrum type predict the disappearance of orthopositronium (o-Ps) into
additional dimension(s). The experimental signature of this effect is the o-Ps
-> invisible decay of orthopositronium which may occur at a rate within three
orders of magnitude of the present experimental upper limit. This result
enhances existing motivations for a more sensitive search for this decay mode
and suggests additional directions for testing extra dimensions in non
accelerator experiments.Comment: 3 pages, to appear in Phys. Rev.
Extraction of Black Hole Geometry in Exactly Quantized Two Dimensional Dilaton Gravity
Based on our previous work, in which a model of two dimensional dilaton
gravity of the type proposed by Callan, Giddings, Harvey and Strominger was
rigorously quantized, we explicitly demonstrate how one can extract space-time
geometry in exactly solvable theory of quantum gravity. In particular, we have
been able to produce a prototypical configuration in which a ( smeared ) matter
shock wave generates a black hole without naked sigularity.Comment: LATEX file 10 pages. UT-Komaba 93-13. 1 figure in postscrip
Radiative Electroweak Breaking with Pseudogoldstone Higgs Doublets
We consider a realistic example of supersymmetric grand unification based on
in which the electroweak (EW) higgs
doublets are `light' as a consequence of the `pseudogoldstone' mechanism. We
discuss radiative EW breaking in this model, exploring in particular the
`small' (order unity) and `large' regions by
studying the variations of , where
are the well known MSSM parameters evaluated at the GUT scale.
For sufficiently close to unity the quantity can be of order
unity, but the converse is not always true.Comment: 18 pages plain LaTeX (to be run twice) and 11 figures available
separately from uuencoded file
Quantum-well-laser mirror degradation investigated by microprobe optical spectroscopy
A study of facet degradation of InGaAs quantum well lasers is reported. We tune up a Raman and photoluminescence micro-probe technique for determining the crystal structure and the temperature profile of the cladding layer, in steps of approximately 1 micrometer, with a temperature resolution better than 1 degree Kelvin. The cladding layer composition and cross- section temperature profile have been monitored during operation. A clear correlation between the facet degradation and the type of protective coating is found
Nonanomalous Discrete R-Symmetry and Light Gravitino
We discuss nonanomalous R-symmetry in the supersymmetric grand unified
theories. In particular, we explore anomaly-free solutions predicting the
gravitino mass in the range of 10^{-3} eV \lsim m_{3/2} \lsim 1 TeV when the
-parameter is fixed to be . In the minimal SU(5) GUT, we
have shown that is obtained only if the gravitino is
ultralight with mass . If extra fields or are introduced, many solutions
predicting m_{3/2} \gsim 10^{-3} eV are found. The R-parity is violated due
to the vacuum expectation value of the superpotential, but it is controlled by
the discrete R-symmetry. We find that the R-parity violating couplings are
naturally suppressed much below the experimental bounds for some charge
assignments. These charge assignments predict light gravitino with masses of
order --. These discrete R-symmetries
can be considered as solutions to the -problem in low energy supersymmetry
breaking models such as the gauge mediation.Comment: 20 pages, no figure. v2: minor corrections, references added, "Note
Added" in Summary adde
Searches for New Particles/Phenomena at CDF
Recent results from the searches for new particles and phenomena using data collected by CDF are presented. Most results are from the data taken during 1994-95 period (Run I), but some preliminary results from the current data taking period (Run IIa) are presented as well
A Unified Approach to Solvable Models of Dilaton Gravity in Two-Dimensions Based on Symmetry
A large class of solvable models of dilaton gravity in two space-time
dimensions, capable of describing black hole geometry, are analyzed in a
unified way as non-linear sigma models possessing a special symmetry. This
symmetry, which can be neatly formulated in the target-space-covariant manner,
allows one to decompose the non-linearly interacting dilaton-gravity system
into a free field and a field satisfying the Liouville equation with in general
non-vanishing cosmological term. In this formulation, all the existent models
are shown to fall into the category with vanishing cosmological constant.
General analysis of the space-time structureinduced by a matter shock wave is
performed and new models, with and without the cosmological term, are
discussed.Comment: 29 pages, LaTe
Higgs Bosons Production with Photons at Lepton-Antilepton Colliders
By model independent way scalar and pseudoscalar neutral Higgs boson
production with photon in the tree process are
considered.For the Standard Model and Minimal Supersymmetric Standard Model
cases numerical estimates are obtained.The model independent flavour changing
Higgs bosons production in the tree processes is also considered.Comment: 12 pages, LaTeX file, using eps.sty, 4 ps figures include
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