4,325 research outputs found
Implications of Non-universal Soft Masses on Gauge Coupling Unification
We study the gauge coupling unification of the minimal supersymmetric
standard model with non-universal soft scalar and gaugino masses. The
unification scale of the gauge couplings is estimated for non-universal cases.
It is sensitive to the non-universality. It turns out that these cases can be
combined with the assumption of string unification, which leads to a prediction
of and , the normalisation of the
generator. String unification predicts . These values have
non-trivial implications on string model building. Two-loop corrections are
also calculated. Some of these cases exhibit a large discrepancy between
experiment and string unification. We calculate string threshold corrections to
explain the discrepancy.Comment: 25 pages, Latex, 4 figures (not included
Probing SO(10) symmetry breaking patterns through sfermion mass relations
We consider supersymmetric SO(10) grand unification where the unified gauge
group can break to the Standard Model gauge group through different chains. The
breaking of SO(10) necessarily involves the reduction of the rank, and
consequent generation of non-universal supersymmetry breaking scalar mass
terms. We derive squark and slepton mass relations, taking into account these
non-universal contributions to the sfermion masses, which can help distinguish
between the different chains through which the SO(10) gauge group breaks to the
Standard Model gauge group. We then study some implications of these
non-universal supersymmetry breaking scalar masses for the low energy
phenomenology.Comment: 13 pages, latex using revtex4, contains 2 figures, replaced with
version accepted for publicatio
Implications of non-universality of soft terms in supersymmetric grand unified theories
Most discussions of supersymmetric grand unified theories assume universality
of the soft supersymmetry breaking terms at the grand scale. We point out that
the behaviour of these theories might change significantly in the presence of
non--universal soft terms. Particularly in SO(10)--like models with a large
value of tan we observe a decisive change of predictions, allowing the
presence of relatively light gauginos as well as small supersymmetric
corrections to the b--quark mass. Some results remain rather stable, including
the -- correlation. Models with small tan seem to be less
affected by non--universality which mainly leads to the new possibility of
small (i.e. the squark and slepton soft mass parameter), excluded in
the universal case.Comment: 15 pages (Latex) plus 5 figures (uuencoded postscript file). TUM-HEP
201/9
Crosschecks for Unification at the LHC
Experiments at the Large Hadron Collider (LHC) might test the picture of
supersymmetric Grand Unification in particle physics. We argue that the
identification of gaugino masses is the most promising step in this direction.
Mass predictions for gauginos are pretty robust and often related to the values
of the gauge couplings constants. They might allow a meaningful crosscheck for
grand unification, at least in simple schemes like gravity, anomaly or mirage
mediation.Comment: 23 pages, 8 figure
Sparticle Mass Spectrum in Grand Unified Theories
We carry out a detailed analysis of sparticle mass spectrum in supersymmetric
grand unified theories. We consider the spectroscopy of the squarks and
sleptons in SU(5) and SO(10) grand unified theories, and show how the
underlying supersymmetry breaking parameters of these theories can be
determined from a measurement of different sparticle masses. This analysis is
done analytically by integrating the one-loop renormalization group equations
with appropriate boundary conditions implied by the underlying grand unified
gauge group. We also consider the impact of non-universal gaugino masses on the
sparticle spectrum, especially the neutralino and chargino masses which arise
in supersymmetric grand unified theories with non-minimal gauge kinetic
function. In particular, we study the interrelationships between the squark and
slepton masses which arise in grand unified theories at the one-loop level,
which can be used to distinguish between the different underlying gauge groups
and their breaking pattern to the Standard Model gauge group. We also comment
on the corrections that can affect these one-loop results.Comment: 19 pages, 6 figure
Non-Universal Gaugino Masses in Supersymmetric SO(10)
We consider SUSY SO(10) models in which SUSY breaking occurs via an F-term
which does not transform as an SO(10) singlet. This results in non-universal
GUT-scale gaugino masses leading to a different pattern of sparticle masses
from what is expected in the minimal supergravity model (mSUGRA). We study
three breaking chains of SO(10) down to the standard model through
SU(4)\timesSU(2)\timesSU(2), SU(2)SO(7) and `flipped' SU(5) achieved
by the representations 54 and 210 which appear in the symmetric product of two
SO(10) adjoints. We examine the phenomenological implications of the different
boundary conditions corresponding to the different breaking chains and present
the sparticle spectrum.Comment: 23 pages, 3 figures, 2 tables, corrected typos, discussion and
references added, final version accepted for publication on NP
Supergravity Unified Models
The development of supergravity unified models and their implications for
current and future experiments are discussed.Comment: Latex, 21 pages, to appear in book "Perspectives on Supergravity",
World Scientific, Editor G. Kane; reference numbers and minor typos correcte
Prospects for the direct detection of neutralino dark matter in orbifold scenarios
We analyse the phenomenology of orbifold scenarios from the heterotic
superstring, and the resulting theoretical predictions for the direct detection
of neutralino dark matter. In particular, we study the parameter space of these
constructions, computing the low-energy spectrum and taking into account the
most recent experimental and astrophysical constraints, as well as imposing the
absence of dangerous charge and colour breaking minima. In the remaining
allowed regions the spin-independent part of the neutralino-proton cross
section is calculated and compared with the sensitivity of dark matter
detectors. In addition to the usual non universalities of the soft terms in
orbifold scenarios due to the modular weight dependence, we also consider
D-term contributions to scalar masses. These are generated by the presence of
an anomalous U(1), providing more flexibility in the resulting soft terms, and
are crucial in order to avoid charge and colour breaking minima. Thanks to the
D-term contribution, large neutralino detection cross sections can be found,
within the reach of projected dark matter detectors.Comment: 51 pages, 25 figure
Higgs and Supersymmetric Particle Signals at the Infrared Fixed Point of the Top Quark Mass
We study the properties of the Higgs and supersymmetric particle spectrum
associated with the infrared fixed point solution of the top quark mass in the
MSSM. We concentrate on the possible detection of these particles, analysing
the deviations from the Standard Model predictions for the leptonic and
hadronic variables measured at LEP and for the decay rate . We consider the low and moderate regime, and we study
both, the cases of universal and non--universal soft supersymmetry breaking
parameters at high energies. In the first case, for any given value of the top
quark mass, the Higgs and sparticle spectra are completely determined as a
function of two soft supersymmetry breaking parameters. In the case of
non--universality, instead, the strong correlations between the sparticle
masses are relaxed, allowing a richer structure for the precision data
variables. We show, however, that the requirement that the low energy theory
proceeds from a grand unified theory with a local symmetry group including
, strongly constrains the set of possible indirect experimental
signatures. As a general feature, whenever a significant deviation from the
Standard Model value of the precision data variables is predicted, a light
sparticle, visible at LEP2, appears in the spectrum.Comment: 42 pages, 16 figures (not included), CERN-TH.7393/9
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