80 research outputs found
Are light sneutrinos buried in LEP data?
Supersymmetry may resolve the disagreement between the precision electroweak
data and the direct limit on the higgs mass, if there are light sneutrinos in
the mass range 55 GeV < m_{\snu} < 80 GeV. Such sneutrinos should decay
invisibly with 100% branching ratio and contribute to the + missing
energy signal, investigated by all the LEP groups. It is shown that while the
data accumulated by a single group may not be adequate to reveal such
sneutrinos, a combined analysis of the data collected by all four groups will
be sensitive to m_{\snu} in the above range. If no signal is found a lower
bound on m_{\snu} stronger than that obtained from the -pole data may
emerge.Comment: 12 pages, LaTeX, 1 postscript figure included, uses epsfig.sty Minor
revisions in the discussion of future prospects, 1 ref adde
in lepton number model with a right-handed neutrino
We perform a detailed study of the signal rate of the lightest Higgs boson in
the diphoton channel (), recently analyzed by both the
ATLAS and CMS collaborations at the Large Hadron Collider, in the framework of
lepton number model with a right handed neutrino superfield. The
corresponding neutrino Yukawa coupling, `', plays a very important role in
the phenomenology of this model. A large value of provides
an additional tree level contribution to the lightest Higgs boson mass along
with a very light (mass a few hundred MeV) bino like neutralino and a
small tree level mass of one of the active neutrinos that is compatible with
various experimental results. In the presence of this light neutralino, the
invisible decay width of the Higgs boson can become important. We studied this
scenario in conjunction with the recent LHC results. The signal rate
obtained in this scenario is compatible with the recent
results from both the ATLAS and the CMS collaborations at 1 level. A
small value of `', on the other hand, is compatible with a sterile neutrino
acting as a 7 keV dark matter that can explain the observation of a
mono-energetic X-ray photon line by the XMM-Newton X-ray observatory. We also
study the impact of in this case.Comment: 45 pages, Corrected a sign error in the numerical code and included
the correct symmetry factor in Eq.(B.8). One figure removed, some
modifications in the text, conclusions partially changed. Erratum published
in JHE
Effects of SO(10) D-Terms on SUSY Signals at the Tevatron
We study signals for the production of superparticles at the Tevatron in
supergravity scenarios based on the Grand Unified group SO(10). The breaking of
this group introduces extra contributions to the masses of all scalars,
described by a single new parameter. We find that varying this parameter can
considerably change the size of various expected signals studied in the
literature, with different numbers of jets and/or charged leptons in the final
state. The ratios of these signal can thus serve as a diagnostic to detect or
constrain deviations from the much--studied scenario where all scalar masses
are universal at the GUT scale. Moreover, under favorable circumstances some of
these signals, and/or new signals involving hard jets, should be observable
at the next run of the Tevatron collider even if the average scalar mass lies
well above the gluino mass.Comment: 17 pages, LaTeX including 3 postscript figures, uses equation.st
Associated Higgs Production in CP-violating supersymmetry: probing the `open hole' at the Large Hadron Collider
A benchmark CP-violating supersymmetric scenario (known in the literature as
`CPX-scenario') is studied in the context of the Large Hadron Collider (LHC).
It is shown that the LHC, with low to moderate accumulated luminosity, will be
able to probe the existing `hole' in the - plane, which
cannot be ruled out by the Large Electron Positron Collider data. This can be
done through associated production of Higgs bosons with top quark and top
squark pairs leading to the signal \emph{dilepton + jets (including 3
b-jets) + missing }. Efficient discrimination of such a CP-violating
supersymmetric scenario from other contending ones is also possible at the LHC
with a moderate volume of data.Comment: LaTeX, 19 pages, 5 figures, added references for section 2, typos
correcte
LHC Signature of the Minimal SUGRA Model with a Large Soft Scalar Mass
Thanks to the focus point phenomenon, it is quite {\it natural} for the
minimal SUGRA model to have a large soft scalar mass m_0 > 1 TeV. A distinctive
feature of this model is an inverted hierarchy, where the lighter stop has a
significantly smaller mass than the other squarks and sleptons. Consequently,
the gluino is predicted to decay dominantly via stop exchange into a channel
containing 2b and 2W along with the LSP. We exploit this feature to construct a
robust signature for this model at the LHC in leptonic channels with 3-4 b-tags
and a large missing-E_T.Comment: Small clarifications added. Final version to appear in Phys. Lett.
Exploring viable vacua of the -symmetric NMSSM
We explore the vacua of the -symmetric Next-to-Minimal Supersymmetric
Standard Model (NMSSM) and their stability by going beyond the simplistic
paradigm that works with a tree-level neutral scalar potential and adheres to
some specific flat directions in the field space. Key effects are demonstrated
by first studying the profiles of this potential under various circumstances of
physical interest via a semi-analytical approach. The results thereof are
compared to the ones obtained from a dedicated package like \veva ~which
further incorporates the thermal effects to the potential. Regions of the
phenomenological NMSSM (pNMSSM) parameter space that render the desired
symmetry breaking (DSB) vacuum absolutely stable, long- or short-lived (in
relation to the age of the Universe) under quantum/thermal tunneling are
delineated. Regions that result in color and charge breaking (CCB) minima are
also presented. It is demonstrated that light singlet scalars along with a
light LSP (lightest supersymmetric particle) having an appreciable singlino
admixture are compatible with a viable DSB vacuum and are much relevant for the
collider experiments.Comment: 52 pages, 19 figures, 4 tables; matches with published versio
Testing Gauge-Gravitino Coupling in Gauge-Mediated Supersymmetry Breaking Through Single Photon Events
We show that the process missing energy, arising from
the pair production of neutralinos, can probe the \gamma-\tilde\gamma-
\gravitino as well as the Z-\tilde Z-\gravitino couplings in Gauge Mediated
Supersymmetry Breaking models. This enables one to study the mutual
relationship of the Goldstino couplings of the different gauginos, a feature
whose testability has not been emphasized so far. The Standard Model
backgrounds get suppresed with the use of a right polarized electron beam. The
energy and angular distribution of the emitted photon can distinguish such
models from the minimal supersymmetric theory and its variants.Comment: Revised version to be published in Physics Letters B. Some minor
changes were mad
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