2,245 research outputs found
LIGHT PHOTINOS AS DARK MATTER
There are good reasons to consider models of low-energy supersymmetry with
very light photinos and gluinos. In a wide class of models the lightest
-odd, color-singlet state containing a gluino, the , has a mass in the
1-2 GeV range and the slightly lighter photino, \pho, would survive as the
relic -odd species. For the light photino masses considered here, previous
calculations resulted in an unacceptable photino relic abundance. But we point
out that processes other than photino self-annihilation determine the relic
abundance when the photino and are close in mass. Including
\r0\longleftrightarrow\pho processes, we find that the photino relic
abundance is most sensitive to the -to-\pho mass ratio, and within model
uncertainties, a critical density in photinos may be obtained for an
-to-\pho mass ratio in the range 1.2 to 2.2. We propose photinos in the
mass range of 500 MeV to 1.6 GeV as a dark matter candidate, and discuss a
strategy to test the hypothesis.Comment: uuencoded compressed tar file containing 32 page LaTeX file and eight
postscript figure
Experiments to Find or Exclude a Long-Lived, Light Gluino
Gluinos in the mass range ~1 1/2 - 3 1/2 GeV are absolutely excluded. Lighter
gluinos are allowed, except for certain ranges of lifetime. Only small parts of
the mass-lifetime parameter space are excluded for larger masses unless the
lifetime is shorter than ~ 2 10^{-11} (m_{gluino}/ GeV) sec. Refined mass and
lifetime estimates for R-hadrons are given, present direct and indirect
experimental constraints are reviewed, and experiments to find or definitively
exclude these possibilities are suggested.Comment: 27 pp, latex with 1 uufiled figure, RU-94-35. New version amplifies
discussion of some points and corresponds to version for Phys. Rev.
Correlation between Compact Radio Quasars and Ultra-High Energy Cosmic Rays
Some proposals to account for the highest energy cosmic rays predict that
they should point to their sources. We study the five highest energy events
(E>10^20 eV) and find they are all aligned with compact, radio-loud quasars.
The probability that these alignments are coincidental is 0.005, given the
accuracy of the position measurements and the rarity of such sources. The
source quasars have redshifts between 0.3 and 2.2. If the correlation pointed
out here is confirmed by further data, the primary must be a new hadron or one
produced by a novel mechanism.Comment: 8 pages, 3 tables, revtex. with some versions of latex it's necessary
to break out the tables and latex them separately using article.sty rather
than revtex.st
Fission and cluster decay of Sr nucleus in the ground-state and formed in heavy-ion reactions
Calculations for fission and cluster decay of are presented for
this nucleus to be in its ground-state or formed as an excited compound system
in heavy-ion reactions. The predicted mass distribution, for the dynamical
collective mass transfer process assumed for fission of , is clearly
asymmetric, favouring -nuclei. Cluster decay is studied within a
preformed cluster model, both for ground-state to ground-state decays and from
excited compound system to the ground-state(s) or excited states(s) of the
fragments.Comment: 14 pages LaTeX, 5 Figures available upon request Submitted to Phys.
Rev.
Exclusive Hadronic Processes and Color Transparency
We review the current status of high energy exclusive processes and color
transparency.Comment: 17 pages, 8 figures, based on talk given at International Symposium
on Nuclear Physics, Mumbai, Dec 18-22, 200
Sum Rule Description of Color Transparency
The assumption that a small point-like configuration does not interact with
nucleons leads to a new set of sum rules that are interpreted as models of the
baryon-nucleon interaction. These models are rendered semi-realistic by
requiring consistency with data for cross section fluctuations in proton-proton
diffractive collisions.Comment: 22 pages + 3 postscript figures attache
in Symmetric Supersymmetry
We compute the one-loop corrections to the vertex in the
symmetric minimal supersymmetric extension of the standard model. We
find that the predicted value of is consistent with experiment if the
mass of the lighter top squark is no more than 180 GeV. Furthermore, other data
combines to place a lower bound of 88 GeV on the mass of the light top squark.
A top squark in this mass range should be accessible to searches by experiments
at FNAL and LEP.Comment: Corrected typos; added footnotes and a reference. 19 pages, LaTeX,
includes 8 figures, full postscript version at
http://smyrd.bu.edu/htfigs/htfigs.htm
Searching for in t \tbar Production
The triple gluon field strength operator represents the only genuinely
gluonic CP conserving term which can appear at dimension-6 within an effective
strong interaction Lagrangian. Previous studies of this operator have revealed
that its effect on gluon scattering is surprisingly difficult to detect. In
this article, we analyze the impact of upon top quark pair production. We
find that it will generate observable cross section deviations from QCD at the
LHC for even relatively small values of its coefficient. Furthermore,
affects the transverse momentum distribution of the produced top quarks more
strongly at high energies than dimension-6 four-quark and chromomagnetic moment
terms in the effective Lagrangian. Top-antitop production at the LHC will
therefore provide a sensitive and clean probe for the elusive triple gluon
field strength operator.Comment: 20 pages, 8 figures (3 updated figures not included but available
upon request), CALT-68-1941, BUHEP-94-18. (Some previously overlooked graphs
are now included. Our conclusions remain unchanged.
Fixed-Angle Elastic Hadron Scattering
The scattering amplitude in the dual model with Mandelstam analyticity and
trajectory is studied in the limit By
using the saddle point method, a series decomposition for the scattering
amplitude is obtained, with the leading and two sub-leading terms calculated
explicitly.Comment: 15 pages, LaTeX, 2 figures with eps file
An analysis of a Heavy Gluino LSP at CDF : The Heavy Gluino Window
In this paper we consider a heavy gluino to be the lightest supersymmetric
particle [LSP]. We investigate the limits on the mass of a heavy gluino LSP,
using the searches for excess events in the jets plus missing momentum channel
in Run I. The neutral and charged R-hadrons, containing a heavy gluino LSP,
have distinct signatures at the Fermilab Tevatron. The range of excluded gluino
masses depends on whether the R-hadron is charged or neutral and the amount of
energy deposited in the hadronic calorimeter. The latter depends on the energy
loss per collision in the calorimeter and the number of collisions; where both
quantities require a model for R-hadron- Nucleon scattering. We show how the
excluded range of gluino mass depends on these parameters. We find that gluinos
with mass in the range between GeV and GeV are excluded by
CDF Run I data. Combined with previous results of Baer et al., which use LEP
data to exclude the range 3 - 2225 GeV, our result demonstrates that an
allowed window for a heavy gluino with mass between 25 and 35 GeV is quite
robust. Finally we discuss the relevant differences of our analysis of Tevatron
data to that of Baer et al.Comment: 36 pages, 11 figures, added an acknowledgemen
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