10 research outputs found
Phenomenological implications of sterile neutrinos in the SSM and dark matter
We analyze the role of sterile neutrinos in the framework of the SSM,
where the presence of right-handed neutrinos provides a simultaneous solution
to - and -problems in supersymmetry. We adopt a minimalistic
approach, reproducing light neutrino masses and mixing angles at tree level
using just two right-handed neutrinos as part of the seesaw mechanism. A third
right-handed neutrino does not contribute significantly to the mass of the
three active ones, behaving as a sterile neutrino with a mass in the range
keVMeV. Furthermore, a sterile neutrino of about keV can be a good
candidate for dark matter with a lifetime larger than the age of the Universe.
In particular, the three-body decay to active neutrinos gives the dominant
contribution to its lifetime. The one-loop decay to gamma and active neutrino
is subdominant, but relevant for observations such as astrophysical X-rays. We
find regions of the parameter space of the SSM, with different values
of the sterile neutrino mass, fulfilling not only these constraints but also
collider constraints from the Higgs sector.Comment: Version published in Astroparticle Physics. Discussion improved
including one figure. 24 pages, 7 figures, 2 table
Hunting physics beyond the standard model with unusual and decays
Nonstandard on-shell decays of and bosons are possible within the
framework of extended supersymmetric models, i.e., with singlet states and/or
new couplings compared to the minimal supersymmetric standard model. These
modes are typically encountered in regions of the parameter space with light
singlet-like scalars, pseudoscalars, and neutralinos. In this letter we
emphasize how these states can lead to novel signals at colliders from - or
-boson decays with prompt or displaced multileptons/tau
jets/jets/photons in the final states. These new modes would give distinct
evidence of new physics even when direct searches remain unsuccessful. We
discuss the possibilities of probing these new signals using the existing LHC
run-I data set. We also address the same in the context of the LHC run-II, as
well as for the future colliders. We exemplify our observations with the "
from " supersymmetric standard model, where three generations of
right-handed neutrino superfields are used to solve shortcomings of the minimal
supersymmetric standard model. We also extend our discussion for other variants
of supersymmetric models that can accommodate similar signatures.Comment: New discussions and references added, 8 pages, 1 figure, matches with
the published version in Phys. Rev.
Probing the " from " supersymmetric standard model with displaced multileptons from the decay of a Higgs boson at the LHC
The " from " supersymmetric standard model (SSM) cures the
-problem and concurrently reproduces measured neutrino data by using a set
of usual right-handed neutrino superfields. Recently, the LHC has revealed the
first scalar boson which naturally makes it tempting to test SSM in the
light of this new discovery. We show that this new scalar while decaying to a
pair of unstable long-lived neutralinos, can lead to a distinct signal with
non-prompt multileptons. With concomitant collider analysis we show that this
signal provides an unmistakable signature of the model, pronounced with light
neutralinos. Evidence of this signal is well envisaged with sophisticated
displaced vertex analysis, which deserves experimental attention.Comment: 5 pages, 3 figures, title, text, abstract and references modifie
Looking for the left sneutrino LSP with displaced-vertex searches
We analyze a displaced dilepton signal expected at the LHC for a tau left
sneutrino as the lightest supersymmetric particle with a mass in the range
- GeV. The sneutrinos are pair produced via a virtual , or
in the channel and, given the large value of the tau Yukawa
coupling, their decays into two dileptons or a dilepton plus missing transverse
energy from neutrinos can be significant. The discussion is carried out in the
SSM, where the presence of -parity violating couplings involving
right-handed neutrinos solves the problem and can reproduce the neutrino
data. To probe the tau left sneutrinos we compare the predictions of the SSM with the ATLAS search for long-lived particles using displaced lepton
pairs in collisions at TeV, allowing us to constrain the
parameter space of the model. We also consider an optimization of the trigger
requirements used in existing displaced-vertex searches by means of a High
Level Trigger that exploits tracker information. This optimization is
generically useful for a light metastable particle decaying into soft charged
leptons. The constraints on the sneutrino turn out to be more stringent. We
finally discuss the prospects for the TeV LHC searches as well as further
potential optimizations.Comment: Version published in PRD, discussions expanded, references added, LEP
and LHC constraints discussed in more detail, 29 pages, 9 figures, 9 table
Dark matter candidates in the NMSSM with RH neutrino superfields
R-parity conserving supersymmetric models with right-handed (RH) neutrinos
are very appealing since they could naturally explain neutrino physics and also
provide a good dark matter (DM) candidate such as the lightest supersymmetric
particle (LSP). In this work we consider the next-to-minimal supersymmetric
standard model (NMSSM) plus RH neutrino superfields, with effective Majorana
masses dynamically generated at the electroweak scale (EW). We perform a scan
of the relevant parameter space and study both possible DM candidates: RH
sneutrino and neutralino. Especially for the case of RH sneutrino DM we analyse
the intimate relation between both candidates to obtain the correct amount of
relic density. Besides the well-known resonances, annihilations through scalar
quartic couplings and coannihilation mechanisms with all kind of neutralinos,
are crucial. Finally, we present the impact of current and future direct and
indirect detection experiments on both DM candidates.Comment: Version published in JCAP, 40 pages, 8 figures, 6 table
Probing the SSM with light scalars, pseudoscalars and neutralinos from the decay of a SM-like Higgs boson at the LHC
The " from " supersymmetric standard model (SSM) can
accommodate the newly discovered Higgs-like scalar boson with a mass around 125
GeV. This model provides a solution to the -problem and simultaneously
reproduces correct neutrino physics by the simple use of right-handed neutrino
superfields. These new superfields together with the introduced -parity
violation can produce novel and characteristic signatures of the SSM at
the LHC. We explore the signatures produced through two-body Higgs decays into
the new states, provided that these states lie below in the mass spectrum. For
example, a pair produced light neutralinos depending on the associated decay
length can give rise to displaced multi-leptons/taus/jets/photons with
small/moderate missing transverse energy. In the same spirit, a Higgs-like
scalar decaying to a pair of scalars/pseudoscalars can produce final states
with prompt multi-leptons/taus/jets/photons.Comment: 58 pages, 3 figures, three new references added, matches with the
published version in JHE
Right-handed sneutrino and gravitino multicomponent dark matter in light of neutrino detectors
We investigate the possibility that right-handed (RH) sneutrinos and
gravitinos can coexist and explain the dark matter (DM) problem. We compare
extensions of the minimal supersymmetric standard model (MSSM) and the
next-to-MSSM (NMSSM) adding RH neutrinos superfields, with special emphasis on
the latter. If the gravitino is the lightest supersymmetric particle (LSP) and
the RH sneutrino the next-to-LSP (NLSP), the heavier particle decays to the
former plus left-handed (LH) neutrinos through the mixing between the scalar
partners of the LH and RH neutrinos. However, the interaction is suppressed by
the Planck mass, and if the LH-RH sneutrino mixing parameter is small, , a long-lived RH sneutrino NLSP is possible even surpassing the age
of the Universe. As a byproduct, the NLSP to LSP decay produces monochromatic
neutrinos in the ballpark of current and planned neutrino telescopes like
Super-Kamiokande, IceCube and Antares that we use to set constraints and show
prospects of detection. In the NMSSM+RHN, assuming a gluino mass parameter TeV we found the following lower limits for the gravitino mass GeV and the reheating temperature GeV, for GeV. If we take TeV,
then the limits on are relaxed by one order of magnitude.Comment: 30 pages, 7 figures, 1 tabl