770 research outputs found
Natural emergence of neutrino masses and dark matter from -symmetry
We propose a supersymmetric extension of the Standard Model (SM) with a
continuous global symmetry. The -charges of the SM fields are
identified with that of their lepton numbers. As a result, both bilinear and
trilinear `-parity violating' (RPV) terms could be present at the
superpotential. However, -symmetry is not an exact symmetry as it is broken
by supergravity effects. Hence, sneutrinos acquire a small vacuum expectation
value in this framework. However, a suitable choice of basis ensures that the
bilinear RPV terms can be completely rotated away from the superpotential and
the scalar potential. On the other hand, the trilinear terms play a very
crucial role in generating neutrino masses and mixing at the tree level. This
is noticeably different from the typical -parity violating Minimal
Supersymmetric Standard Model. Also, gravitino mass turns out to be the order
parameter of -breaking and is directly related to the neutrino mass. We show
that such a gravitino, within the mass range can be an excellent dark matter candidate.
Finally, we looked into the collider implications of our framework.Comment: 23 pages, one figure (added), title changed, discussion added on
sneutrino vev basis, accepted for publication in JHE
Higgs boson mass, neutrino masses and mixing and keV dark matter in an lepton number model
We discuss neutrino masses and mixing in the framework of a supersymmetric
model with an symmetry, consisting of a single right handed neutrino
superfield with an appropriate R charge. The lepton number () of the
standard model fermions are identified with the negative of their R-charges. As
a result, a subset of leptonic R-parity violating operators can be present and
are consistent with the symmetry. This model can produce one light
Dirac neutrino mass at the tree level without the need of introducing a very
small neutrino Yukawa coupling. We analyze the scalar sector of this model in
detail paying special attention to the mass of the lightest Higgs boson. One of
the sneutrinos might acquire a substantial vacuum expectation value leading to
interesting phenomenological consequences. Different sum rules involving the
physical scalar masses are obtained and we show that the lightest Higgs boson
mass receives a contribution proportional to the square of the neutrino Yukawa
coupling . This allows for a 125 GeV Higgs boson at the tree level for and still having a small tree level mass for the active
neutrino. In order to fit the experimental results involving neutrino masses
and mixing angles we introduce a small breaking of symmetry, in the
context of anomaly mediated supersymmetry breaking. In the presence of this
small R-symmetry breaking, light neutrino masses receive contributions at the
one-loop level involving the R-parity violating interactions. We also identify
the right handed sterile neutrino as a warm dark matter candidate in our model.
In the case of R-symmetry breaking, the large case is characterized by a
few hundred MeV lightest neutralino as an unstable lightest supersymmetric
particle (LSP) and we briefly discuss the cosmological implications of such a
scenario.Comment: Minor corrections in the text, figure 9.6 and 9.7 modified, eq. (66)
added, matches with the published version in JHE
Constraining compressed versions of MUED and MSSM using soft tracks at the LHC
A compressed spectrum is an anticipated hideout for many beyond standard
model scenarios. Such a spectrum naturally arises in the minimal universal
extra dimension framework and also in supersymmetric scenarios. Low
leptons and jets are characteristic features of such situations. Hence, a
monojet with has been the conventional signal at the Large Hadron
Collider (LHC). However, we stress that inclusion of -binned track
observables from such soft objects provide very efficient discrimination of new
physics signals against various SM backgrounds. We consider two benchmark
points each for minimal universal extra dimension (MUED) and minimal
supersymmetric standard model (MSSM) scenarios. We perform a detailed cut-based
and multivariate analysis (MVA) to show that the new physics parameter space
can be probed in the ongoing run of LHC at 13 TeV center-of-mass energy with an
integrated luminosity 20-50 fb. When studied in conjunction with
the dark matter relic density constraint assuming standard cosmology, we find
that compressed MUED (with ) can be already excluded from the
existing data. Also, MVA turns out to be a better technique than regular
cut-based analysis since tracks provide uncorrelated observables which would
extract more information from an event.Comment: 26 pages, 7 figures. Minor modifications in the text, references
added, accepted for publication in JHE
Lepton flavour violating decay of 125 GeV Higgs boson to channel and excess in
A recent search for the lepton flavor violating (LFV) decays of the Higgs
boson, performed by CMS collaboration, reports an interesting deviation from
the standard model (SM). The search conducted in the channel and shows an excess of
signal events with 19.7 fb data at a center-of-mass energy
TeV. On the other hand, a search performed by CMS collaboration for
the SM Higgs boson produced in association with a top quark pair ()
also showed an excess in the same-sign di-muon final state. In this work we try
to find out if these two seemingly uncorrelated excesses are related or not.
Our analysis reveals that a lepton flavour violating Higgs decay
() can partially explain the excess in the same sign
di-muon final state in the search, infact brings down the excess
well within 2 error of the SM expectation. Probing such non-standard
Higgs boson decay is of interest and might contain hints of new physics at the
electroweak scale.Comment: 10 pages, 2 figures and 3 table
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
- …