265 research outputs found
Yukawa Coupling Unification in SO(10) Supersymmetric Grand Unified Theories
We report on a preferred region of supersymmetric parameter space by t, b,
tau Yukawa unification. We find a narrow region survives for mu > 0 (suggested
by b --> s gamma and the anomalous magnetic moment of the muon) with A_0 \sim -
2 m_{16}, m_{16} > 1200 GeV, mu, M_{1/2} << m_{16} and tan \beta \sim 50 \pm 2.
Demanding Yukawa unification thus makes definite predictions for Higgs and
sparticle masses.Comment: 4 pages, Talk given at the 9th International Conference on
Supersymmetry and Unification of Fundamental Interactions SUSY'01, June
11--17, Dubna, Russi
The Higgs Penguin and its Applications : An overview
We review the effective Lagrangian of the Higgs penguin in the Standard Model
and its minimal supersymmetric extension (MSSM). As a master application of the
Higgs penguin, we discuss in some detail the B-meson decays into a
lepton-antilepton pair. Furthermore, we explain how this can probe the Higgs
sector of the MSSM provided that some of these decays are seen at Tevatron Run
II and B-factories. Finally, we present a complete list of observables where
the Higgs penguin could be strongly involved.Comment: 22 pages, 6 figures, Invited review article to appear in Mod. Phys.
Lett. A, v2: Table 1 updated, comments and references adde
Supersymmetric Higgs Singlet Effects on B-Meson FCNC Observables at Large tan(beta)
Higgs singlet superfields are usually present in most extensions of the
Minimal Supersymmetric Standard Model (MSSM) that address the mu-problem, such
as the Next-to-Minimal Supersymmetric Standard Model (NMSSM) and the Minimal
Nonminimal Supersymmetric Standard Model (MNSSM). Employing a gauge- and
flavour-covariant effective Lagrangian formalism, we show how the singlet Higgs
bosons of such theories can have significant contributions to B-meson
flavour-changing neutral current (FCNC) observables for large values of
at the 1-loop level. Illustrative results
are presented including effects on the B_s and B_d mass differences and on the
rare decay . In particular, we find that depending on the
actual value of the lightest singlet pseudoscalar mass in the NMSSM, the
branching ratio for can be enhanced or even suppressed with
respect to the Standard Model prediction by more than one order of magnitude.Comment: 28 pages, 8 figures, LaTeX. Minor updates. Version to be published in
PR
Viable models with non-universal gaugino mediated supersymmetry breaking
Recently, extra dimensional SUSY GUT models have been proposed in which
compactification of the extra dimension(s) leads to a breakdown of the gauge
symmetry and/or supersymmetry. We examine a particular class of
higher-dimensional models exhibiting supersymmetry and SU(5) or SO(10) GUT
symmetry. SUSY breaking occurs on a hidden brane, and is communicated to the
visible brane via gaugino mediation. Non-universal gaugino masses are developed
at the compactification scale as a consequence of a restricted gauge symmetry
on the hidden brane. In this case, the compactification scale is at or slightly
below the GUT scale. We examine the parameter space of such models where
gaugino masses are related due to a Pati-Salam symmetry on the hidden brane. We
find limited but significant regions of model parameter space where a viable
spectra of SUSY matter is generated. Our results are extended to the more
general case of three independent gaugino masses; here we find that large
parameter space regions open up for large values of the U(1) gaugino mass M_1.
We also find the relic density of neutralinos for these models to be generally
below expectations from cosmological observations, thus leaving room for hidden
sector states to make up the bulk of cold dark matter. Finally, we evaluate the
branching fraction BF(b -> s gamma) and muon anomalous magnetic moment a_\mu.Comment: 21 pages, 9 figure
New decay modes of heavy Higgs bosons in a two Higgs doublet model with vectorlike leptons
Naturalness and Fine Tuning in the NMSSM: Implications of Early LHC Results
We study the fine tuning in the parameter space of the semi-constrained
NMSSM, where most soft Susy breaking parameters are universal at the GUT scale.
We discuss the dependence of the fine tuning on the soft Susy breaking
parameters M_1/2 and m0, and on the Higgs masses in NMSSM specific scenarios
involving large singlet-doublet Higgs mixing or dominant Higgs-to-Higgs decays.
Whereas these latter scenarios allow a priori for considerably less fine tuning
than the constrained MSSM, the early LHC results rule out a large part of the
parameter space of the semi-constrained NMSSM corresponding to low values of
the fine tuning.Comment: 19 pages, 10 figures, bounds from Susy searches with ~1/fb include
Bi-large Neutrino Mixing and CP violation in an SO(10) SUSY GUT for Fermion Masses
We construct a simple SO(10) SUSY GUT with family symmetry and low
energy R parity. The model describes fermion mass matrices with 14 parameters
and gives excellent fits to 20 observable masses and mixing angles in both
quark and lepton sectors, giving 6 predictions. Bi-large neutrino mixing is
obtained with hierarchical quark and lepton Yukawa matrices; thus avoiding the
possibility of large lepton flavor violation. The model naturally predicts
small 1-3 neutrino mixing, , and a CP violating
phase close to . Among other interesting predictions is a tiny
effective Majorana mass for neutrinoless double-beta decay. Leptogenesis is
also possible with the decay of the lightest right-handed neutrino giving an
acceptable CP violating asymmetry of order , {\em and
with the correct sign for the resultant baryon asymmetry}. We also show how
similar models with the non-abelian symmetry groups SU(2) or , instead of
, can be constructed.Comment: 16 pages, resubmitted as a PLB letter, appendices were remove
Global fits of the Non-Universal Higgs Model
We carry out global fits to the Non-Universal Higgs Model (NUHM), applying
all relevant present-day constraints. We present global probability maps for
the NUHM parameters and observables (including collider signatures, direct and
indirect detection quantities), both in terms of posterior probabilities and in
terms of profile likelihood maps. We identify regions of the parameter space
where the neutralino dark matter in the model is either bino-like, or else
higgsino-like with mass close to 1 TeV and spin-independent scattering cross
section ~ 10^{-9}-10^{-8} pb. We trace the occurrence of the higgsino-like
region to be a consequence of a mild focusing effect in the running of one of
the Higgs masses, the existence of which in the NUHM we identify in our
analysis. Although the usual bino-like neutralino is more prominent,
higgsino-like dark matter cannot be excluded, however its significance strongly
depends on the prior and statistics used to assess it. We note that, despite
experimental constraints often favoring different regions of parameter space to
the Constrained MSSM, most observational consequences appear fairly similar,
which will make it challenging to distinguish the two models experimentallyComment: Major revision following referee comments. Now includes profile
likelihood results. Matches PRD accepted versio
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