3,979 research outputs found
The Higgs Boson Mass as a Probe of the Minimal Supersymmetric Standard Model
Recently, the LEP collaborations have reported a lower bound on a Standard
Model-like Higgs boson of order 89 GeV. We discuss the implications of this
bound for the minimal supersymmetric extension of the Standard Model (MSSM). In
particular, we show that the lower bound on , which can be obtained
from the presently allowed Higgs boson mass value, becomes stronger than the
one set by the requirement of perturbative consistency of the theory up to
scales of order (associated with the infrared fixed-point solution of
the top quark Yukawa coupling) in a large fraction of the allowed parameter
space. The potentiality of future LEP2 searches to further probe the MSSM
parameter space is also discussed.Comment: 15 pages, 5 figures, LateX, psfi
A 125 GeV SM-like Higgs in the MSSM and the rate
We consider the possibility of a Standard Model (SM)-like Higgs in the
context of the Minimal Supersymmetric Standard Model (MSSM), with a mass of
about 125 GeV and with a production times decay rate into two photons which is
similar or somewhat larger than the SM one. The relatively large value of the
SM-like Higgs mass demands stops in the several hundred GeV mass range with
somewhat large mixing, or a large hierarchy between the two stop masses in the
case that one of the two stops is light. We find that, in general, if the
heaviest stop mass is smaller than a few TeV, the rate of gluon fusion
production of Higgs bosons decaying into two photons tends to be somewhat
suppressed with respect to the SM one in this region of parameters. However, we
show that an enhancement of the photon decay rate may be obtained for light
third generation sleptons with large mixing, which can be naturally obtained
for large values of and sizable values of the Higgsino mass
parameter.Comment: 14 pages, 4 figures. Corrected small typos and added reference
Large mass splittings between charged and neutral Higgs bosons in the MSSM
We show that large ( GeV) mass splittings between the charged Higgs
boson () and the neutral Higgs bosons ( and ) are possible in
the Minimal Supersymmetric Standard Model (MSSM). Such splittings occur when
the parameter is considerably larger than the common SUSY scale,
, and have significant consequences for MSSM Higgs searches at future
colliders.Comment: 11 pages, LaTex, 5 figures, version to appear in Phys. Lett.
Do electroweak precision data and Higgs-mass constraints rule out a scalar bottom quark with mass of O(5 GeV)?
We investigate the phenomenological implications of a light scalar bottom
quark, with a mass of about the bottom quark mass, within the minimal
supersymmetric standard model. The study of such a scenario is of theoretical
interest, since, depending on their production and decay modes, light sbottoms
may have escaped experimental detection up to now and, in addition, may
naturally appear for large values of \tan\beta. In this article we show that
such a light sbottom cannot be ruled out by the constraints from the
electroweak precision data and the present bound on the lightest CP-even Higgs
boson mass at LEP. It is inferred that a light sbottom scenario requires in
general a relatively light scalar top quark whose mass is typically about the
top-quark mass. It is also shown that under these conditions the lightest
CP-even Higgs boson decays predominantly into scalar bottom quarks in most of
the parameter space and that its mass is restricted to m_h ~< 123 GeV.Comment: 7 pages, 2 figures, LateX. Discussion about fine tuning and
low-energy experiments enlarged. Version to appear in Phys. Rev. Let
Constraints on split-UED from Electroweak Precision Tests
We present strongly improved electroweak precision constraints on the
split-UED model. We find that the dominating effect arises from contributions
to the muon decay rate by the exchange of even-numbered W-boson Kaluza-Klein
modes at tree-level, which so far have not been discussed in the context of UED
models. The constraints on the split-UED parameter space are translated into
bounds on the mass difference of the first Kaluza-Klein mode of fermions and
the lightest Kaluza-Klein mode, which will be tested is the LHC.Comment: 4 pages, 2 figure
Photon Signatures for Low Energy Supersymmetry Breaking and Broken R-parity
The possible phenomenological consequences of R-parity violating interactions
in the framework of low energy supersymmetry breaking are studied. It is
pointed out that even very weak R-parity violation would completely overshadow
one of the basic signatures of low energy supersymmetry breaking models, that
is, the decay of the next to lightest supersymmetric particle into a photon
(lepton) and missing energy. Thus, the observation of these decays would put
very strong limits on R-parity violating couplings. Vice-versa, if R-parity
violation is established experimentally, before a detailed knowledge of the
spectrum is obtained, it will be very difficult to distinguish gravity mediated
from low energy gauge mediated supersymmetry breaking. Those conclusions are
very model independent. We also comment on the possibility of mixing between
charged and neutral leptons with charginos and neutralinos, respectively, and
its phenomenological consequences for the photon (lepton) signatures, in
scenarios where this mixing is generated by the presence of bilinear or
trilinear R-parity violating terms in the superpotential.Comment: 12 pages, Late
The complementarity of LEP, the Tevatron and the LHC in the search for a light MSSM Higgs boson
We study the properties of the Higgs boson sector in the MSSM, putting
special emphasis on radiative effects which can affect the discovery potential
of the LHC, Tevatron and/or LEP colliders. We concentrate on the V b b-bar
channel, with V=Z or W, and on the channels with diphoton final states, which
are the dominant ones for the search for a light Standard Model Higgs boson at
LEP/Tevatron and LHC, respectively. By analyzing the regions of parameter space
for which the searches in at least one of these colliders can be particularly
difficult, we demonstrate the complementarity of these three colliders in the
search for a light Higgs boson which couples in a relevant way to the W and Z
gauge bosons (and hence plays a relevant role in the mechanism of electroweak
symmetry breaking).Comment: 35 pages, including 11 Postscript figures, using JHEP.cl
Properties of 125 GeV Higgs boson in non-decoupling MSSM scenarios
Tantalizing hints of the Higgs boson of mass around 125 GeV have been
reported at the LHC. We explore the MSSM parameter space in which the 125 GeV
state is identified as the heavier of the CP even Higgs bosons, and study two
scenarios where the two photon production rate can be significantly larger than
the standard model (SM). In one scenario, is
enhanced by a light stau contribution, while the () rate
stays around the SM rate. In the other scenario, is
suppressed and not only the but also the
() rates should be enhanced. The rate can be
significantly larger or smaller than the SM rate in both scenarios. Other
common features of the scenarios include top quark decays into charged Higgs
boson, single and pair production of all Higgs bosons in collisions at
GeV.Comment: 20 pages, 5 figures, accepted version for publication in JHE
Neutrino Masses, Mixing Angles and the Unification of Couplings in the MSSM
In the light of the gathering evidence for neutrino
oscillations, coming in particular from the Super-Kamiokande data on
atmospheric neutrinos, we re-analyze the unification of gauge and Yukawa
couplings within the minimal supersymmetric extension of the Standard Model
(MSSM). Guided by a range of different grand-unified models, we stress the
relevance of large mixing in the lepton sector for the question of bottom-tau
Yukawa coupling unification. We also discuss the dependence of the favoured
value of on the characteristics of the high-energy quark and lepton
mass matrices. In particular, we find that, in the presence of large lepton
mixing, Yukawa unification can be achieved for intermediate values of
that were previously disfavoured. The renormalization-group
sensitivity to the structures of different mass matrices may enable Yukawa
unification to serve as a useful probe of GUT models.Comment: 29 pages, latex, 5 figure
Radiative Electroweak Symmetry Breaking and the Infrared Fixed Point of the Top Quark Mass
The infrared quasi fixed point solution for the top quark mass in the Minimal
Supersymmetric Standard Model explains in a natural way large values of the top
quark mass and appears as a prediction in many interesting theoretical schemes.
Moreover, as has been recently pointed out, for moderate values of ,
in order to achieve gauge and bottom-tau Yukawa coupling unification, the top
quark mass must be within of its fixed point value. In this work we
show that the convergence of the top quark mass to its fixed point value has
relevant consequences for the (assumed) universal soft supersymmetry breaking
parameters at the grand unification scale. In particular, we show that the low
energy parameters do not depend on and but on the combination
. Hence, there is a reduction in the number of
independent parameters. Most interesting, the radiative
breaking condition implies strong correlations between the supersymmetric mass
parameter and the supersymmetry breaking parameters and
or . These correlations, which become stronger for , may have some fundamental origin, which would imply the need of a
reformulation of the naive fine tuning criteria.Comment: 17 pages, 5 figures, CERN-TH.7060/9
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