735 research outputs found
Radiative corrections to the decay H==>hh in the Minimal Supersymmetric Standard Model
We set up a suitable renormalization programme for the one-loop computation
of the decay rate Gamma(H==>hh) in the Minimal Supersymmetric extension of the
Standard Model. We then perform an explicit diagrammatic calculation, including
the full contributions from top, bottom, stop and sbottom loops. We find that,
for tan(beta) close to 1, and m_H greater than or approximately equal to 2 m_t,
the results can significantly differ from those previously obtained in the
effective potential approach. However, the latter method remains a good
approximation in the region of parameter space which is most relevant for H
searches at large hadron colliders.Comment: 11 A4-pages, 3 figures not included, CERN-TH.6603/9
Strings at the Intermediate Scale, or is the Fermi Scale Dual to the Planck Scale?
We show that if the string scale is identifed with the intermediate scale,
GeV, then the notorious hierarchy,
, can be explained using only as small input parameters, where is the
compactification scale. This is possible for weakly-coupled Type-I open-string
vacua if the observed world is assumed to live in an N=1 supersymmetric 3-brane
sector coupled to a separate, hidden, 3-brane world which breaks supersymmetry,
because for such a model . We
discuss some of the phenomenological issues presented by such an
intermediate-scale string, showing that its benefits include:
(i) the possibility of logarithmic gauge-coupling unification of the SM
couplings at ;
(ii) a natural axionic solution to the strong-CP problem with a
phenomenologically-acceptable Peccei-Quinn scale;
(iii) experimentally-interesting neutrino masses, and more.Comment: 16 pages, LaTeX, no figure
On the two-loop sbottom corrections to the neutral Higgs boson masses in the MSSM
We compute the O(ab*as) two-loop corrections to the neutral Higgs boson
masses in the Minimal Supersymmetric Standard Model, using the effective
potential approach. Such corrections can be important in the region of
parameter space corresponding to tan(beta)>>1 and sizeable mu. In spite of the
formal analogy with the O(at*as) corrections, there are important differences,
since the dominant effects are controlled by the sbottom-Higgs scalar
couplings. We propose a convenient renormalization scheme that avoids
unphysically large threshold effects associated with the bottom mass, and
absorbs the bulk of the O(ab*as + ab*at) corrections into the one-loop
expression. We give general explicit formulae for the O(ab*as) corrections to
the neutral Higgs boson mass matrix. We also discuss the importance of the
O(ab^2) corrections and derive a formula for their contribution to mh in a
simple limiting case.Comment: 14 pages, 4 figures. Version to appear in Nucl. Phys.
The decays gluino -> stop_1 b-quark W and gluino -> stop_1 c-quark and phenomenological implications in supersymmetric theories
We show that the decay gluino -> stop_1 b-quark W is important and can even
be dominant in the region of parameter space where it is kinematically allowed.
We discuss phenomenological implications within the Minimal Supersymmetric
Standard Model and models with broken R-parity. We consider the flavour
diagonal case as well as a possible mixing between squarks of different
generations. In the latter case also the decay gluino -> stop_1 c-quark is
potentially important. We show that the decay gluino -> stop_1 b-quark W is
sensitive to the stop mixing angle. Furthermore we demonstrate that in
scenarios with a higgsino--like LSP the gluino decays mainly into final states
containing top quarks or a light stop if allowed by kinematics.Comment: LaTex, 15 pages, 8 figures, uses JHEP3.cls (included), v2, improved
discussion of gluino -> stop_1 c-quark, conclusions unchanged, version to
appear in JHE
Chargino Production at LEP2 in a Supergravity Model
In the framework of a particular supergravity model which provides a natural
solution to the --problem we show how the discovery of a chargino at LEP2
and the measurement of its mass and production cross--section, together with
the measurement of the mass of the lightest neutralino, would determine the
entire Higgs and SUSY spectrum. We give detailed predictions for the Higgs and
SUSY spectrum as a function of the chargino production cross--section, for
constant values of the lightest chargino and gluino masses.Comment: 11 pages, latex, 4 figures uufile
Detecting and Studying in the MSSM: Implications of Supersymmetric Decays and Discriminating GUT Scenarios
We demonstrate that supersymmetric decays, as typified by the predictions of
several GUT-scale boundary condition choices, do not prevent detection of , at a TeV or collider operating
at anticipated luminosity. For much of parameter space the relative branching
ratios for various SUSY and non-SUSY decays can be measured with sufficient
accuracy that different GUT-scale boundary condition choices can be
distinguished from one another at a very high confidence level.Comment: 54 pages, full postscript file also available via anonymous ftp at
ftp://ucdhep.ucdavis.edu/gunion/pair.p
Phenomenological implications of light stop and higgsinos
We examine the phenomenological implications of light and
higgsinos in the Minimal Supersymmetric Standard Model, assuming and heavy and gauginos. In this simplified setting,
we study the contributions to , , , , , and their interplay.Comment: plain LATEX, 6 figures, 23 A4 page
The MSSM invisible Higgs in the light of dark matter and g-2
Giving up the assumption of the gaugino mass unification at the GUT scale,
the latest LEP and Tevatron data still allow the lightest supersymmetric Higgs
to have a large branching fraction into invisible neutralinos. Such a Higgs may
be difficult to discover at the LHC and is practically unreachable at the
Tevatron. We argue that, for some of these models to be compatible with the
relic density, light sleptons with masses not far above the current limits are
needed. There are however models that allow for larger sleptons masses without
being in conflict with the relic density constraint. This is possible because
these neutralinos can annihilate efficiently through a Z-pole. We also find
that many of these models can nicely account, at the 2\sigma level, for the
discrepancy in the latest g-2 measurement. However, requiring consistency with
the g-2 at the 1\sigma level, excludes models that lead to the largest Higgs
branching fraction into LSP's. In all cases one expects that even though the
Higgs might escape detection, one would have a rich SUSY phenomenology even at
the Tevatron, through the production of charginos and neutralinos.Comment: 16 pages and 5 figures. New references added, text and figures
unchange
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