134 research outputs found
Predictions in SU(5) Supergravity Grand Unification with Proton Stability and Relic Density Constraints
It is shown that in the physically interesting domain of the parameter space
of SU(5) supergravity GUT, the Higgs and the Z poles dominate the LSP
annihilation. Here the naive analyses on thermal averaging breaks down and
formulae are derived which give a rigorous treatment over the poles. These
results are then used to show that there exist significant domains in the
parameter space where the constraints of proton stability and cosmology are
simultaneously satisfied. New upper limits on light particle masses are
obtained.Comment: (An error in the reheating factor is corrected, strengthening the
conclusions, i.e. the region in parameter space where the relic density
constraints are satisfied is enlarged.
Testing Supergravity Grand Unification at Future Accelerator and Underground Experiments
The full parameter space of supergravity grand unified theory with
type proton decay is analysed using renormalization
group induced electroweak symmetry breaking under the restrictions that the
universal scalar mass and gluino mass are TeV (no extreme fine
tuning) and the Higgs triplet mass obeys . Future proton
decay experiments at SuperKamiokande or ICARUS can reach a sensitivity for the
mode of yr allowing a number of
predictions concerning the SUSY mass spectrum. Thus either the decay mode will be seen at these experiments or a
chargino of mass GeV will exist and hence be observable
at LEP2. Further, if yr,
then either the light Higgs has mass GeV or GeV i.e. either the light Higgs or the light chargino (or both) would be
observable at LEP2. Thus, the combination of future accelerator and future
underground experiments allow for strong experimental tests of this theory.Comment: 7 figures available upon request, CTP-TAMU-32/93, NUB-TH-3066/93 and
SSCL-Preprint-44
Accurate Cosmological Parmeters and Supersymmetric Particle Properties
Future sattelite, balloon and ground based experiments will give precision
determinations of the basic cosmological parameters and hence determine the
amount of cold dark matter accurately. We consider here two cosmological
models, the nuCDM model and the LambdaCDM model, and examine within the
framework of supergravity grand unification the effect this will have for these
models on supersymmetry searches at accelerators. In the former example the
gluino (neutralino) mass has an upper bound of about 720(100) GeV and gaps
(forbidden regions) may deveop at lower energies. In the latter case the upper
bound occurs at gluino (neutralino) mass of about 520(70) GeV with squarks and
selectron becoming light when gluino (neutralino) masses are greater than
420(55) GeV. Both models are sensitive to non-universal soft breaking masses,
and show a correlation between large (small) dark matter detector rates and low
(high) b -> s+ gamma branching ratio.Comment: RevTeX 10 pages, 4 figure
Constraints on the minimal supergravity model from the b->s+\gamma decay
The constraints on the minimal supergravity model from the b->s+\gamma decay
are studied. A large domain in the parameter space for the model satisfies the
CLEO bound, BR(b->s+\gamma)<5.4X10^{-4}. However, the allowed domain is
expected to diminish significantly with an improved bound on this decay. The
dependence of the b->s+\gamma branching ratio on various parameters is studied
in detail. It is found that, for A_t<0 and the top quark mass within the
vicinity of the center of the CDF value, m_t^{pole}=174\pm17 GeV, there exists
only a small allowed domain because the light stop is tachyonic for most of the
parameter space. A similar phenomenon exists for a lighter top and A_t negative
when the GUT coupling constant is slightly reduced. For A_t>0, however, the
branching ratio is much less sensitive to small changes in m_t, and \alpha_G.Comment: 12 pages, plain tex file, three figures avaliable upon request,
CTP-TAMU-03/94, NUB-TH.7316/94, and CERN-TH.3092/9
Landau Pole Effects and the Parameter Space of the Minimal Supergravity Model
It is shown that analyses at the electroweak scale can be significantly
affected due to Landau pole effects in certain regions of the parameter space.
This phenomenon arises due to a large magnification of errors of the input
parameters , which have currently a 10 percent uncertainty in
their determination. The influence of the Landau pole on the constraint that
the scalar SUSY spectrum be free of tachyons is also investigated.It is found
that this constraint is very strong and eliminates a large portion of the
parameter space.Under the above constraint the trilinear soft SUSY breaking
term at the electroweak scale is found to lie in a restricted domain.Comment: 24 pages,Tex, including 4 figures available on reques
\cl{\bf and Decays in String Models with \e6 Symmetry
A detailed analysis on the rare decay {\it via} \taumue and
\taumus in the string models with \e6 symmetry is reported. It is found
that \Gamma(\taumue)\sim(6-7)\Gamma(\taumus) and these rates are in general
about 1000 times less than that of . It is also
found that the out-going muon in \taumue is almost 100\% right-handed
polarized and the out-going electrons would be predominately parallel to each
other. These decay processes may be accessible at the SSC.Comment: 11 pages, (Plain Tex, four figures not included
Split supersymmetry and the role of a light fermion in a supergravity-based scenario
We investigate split supersymmetry (SUSY) within a supergravity framework,
where local SUSY is broken by the F-term of a hidden sector chiral superfield
X. With reasonably general assumptions, we show that the fermionic component of
X will always have mass within a Tev. Though its coupling to the observable
sector superfields is highly suppressed in Tev scale SUSY, we show that it can
be enhanced by many orders in split SUSY, leading to its likely participation
in accelerator phenomenology.We conclude with a specific example of such a
scenario in a string based supergravity model.Comment: 12 Pages, Latex, Title changed, version thoroughly revise
Non-Universal Soft SUSY Breaking and Dark Matter
An analysis is given of the effects of non-universal soft SUSY breaking
masses in the Higgs sector and in the third generation squark sector, and it is
shown that they are highly coupled. Analytic expressions are obtained for their
effects on the parameters and on the third generation squark masses.
Non-universality effects on dark matter event rates in neutralino-nucleus
scattering are analysed. It is found that the effects are maximal in the range
~GeV where the relic density is governed by the Z and
Higgs poles. In this range the minimum event rates can be increased or
decreased by factors of O(10) depending on the sign of non-universality. Above
this range Landau pole effects arising from the heavy top mass tend to suppress
the non-universality effects. The effect of more precise measurements of
cosmological parameters on event rates, which is expected to occur in the next
round of COBE like sattelite experiments, is also investigated. Implications
for the analysis for dark matter searches are discussed.Comment: 28 pages, latex, and 7 fig
Detecting Physics At The Post-GUT And String Scales By Linear Colliders
The ability of linear colliders to test physics at the post-GUT scale is
investigated. Using current estimates of measurements available at such
accelerators, it is seen that soft breaking masses can be measured with errors
of about (1-20)%. Three classes of models in the post-GUT region are examined:
models with universal soft breaking masses at the string scale, models with
horizontal symmetry, and string models with Calabi-Yau compactifications. In
each case, linear colliders would be able to test directly theoretical
assumptions made at energies beyond the GUT scale to a good accuracy,
distinguish between different models, and measure parameters that are expected
to be predictions of string models.Comment: Latex, 21 pages, no figure
WMAP Data and Recent Developments in Supersymmetric Dark Matter
A brief review is given of the recent developments in the analyses of
supersymmetric dark matter. Chief among these is the very accurate
determination of the amount of cold dark matter in the universe from analyses
using WMAP data. The implications of this data for the mSUGRA parameter space
are analyzed. It is shown that the data admits solutions on the hyperbolic
branch (HB) of the radiative breaking of the electroweak symmetry. A part of
the hyperbolic branch lies in the so called inversion region where the LSP
neutralino becomes essentially a pure Higgsino and degenerate with
the next to the lightest neutralino and the light chargino
. Thus some of the conventional signals for the observation of
supersymmetry at colliders (e.g., the missing energy signals) do not operate in
this region. On the other hand the inversion region contains a high degree of
degeneracy of , , leading to coannihilations
which allow for the satisfaction of the WMAP relic density constraints deep on
the hyperbolic branch. Further, an analysis of the neutralino-proton cross
sections in this region reveals that this region can still be accessible to
dark matter experiments in the future. Constraints from and from
are discussed. Future prospects are also discussed.Comment: 15 pages Latex. Invited talk at the IV International Conference on
Non-accelerator New Physics (NANP'03), Dubna, Russia, June 23-28, 200
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