296 research outputs found
Enhanced lepton flavour violation in the supersymmetric inverse seesaw model
We discuss a supersymmetric inverse seesaw model in which lepton flavour
violating decays can be enhanced either by flavour violating slepton
contributions or by the non-unitarity of the charged current mixing matrix. As
an example we calculate Br(mu -> e gamma) taking into account both heavy lepton
exchange as well as supersymmetric diagrams in a minimal supergravity
framework. We find that the for the same parameters the rate can be enhanced
with respect to seesaw model expectations, with or without supersymmetry.Comment: 16 pages with 2 figure
Neutrino Oscillations in a Supersymmetric SO(10) Model with Type-III See-Saw Mechanism
The neutrino oscillations are studied in the framework of the minimal
supersymmetric SO(10) model with Type-III see-saw mechanism by additionally
introducing a number of SO(10) singlet neutrinos. The light Majorana neutrino
mass matrix is given by a combination of those of the singlet neutrinos and the
active neutrinos. The minimal SO(10) model gives an unambiguous Dirac
neutrino mass matrix, which enables us to predict the masses and the other
parameters for the singlet neutrinos. These predicted masses take the values
accessible and testable by near future collider experiments under the
reasonable assumptions. More comprehensive calculations on these parameters are
also given.Comment: 14 pages, 5 figures; the version to appear in JHE
Determining Heavy Mass Parameters in Supersymmetric SO(10) Models
Extrapolations of soft scalar mass parameters in supersymmetric theories can
be used to explore elements of the physics scenario near the grand unification
scale. We investigate the potential of this method in the lepton sector of
SO(10) which incorporates right-handed neutrino superfields. The method is
exemplified in two models by exploring limits on the precision that can be
expected from coherent LHC and e+e- collider analyses in the reconstruction of
the fundamental scalar mass parameters at the unification scale and of the
D-terms related to the breaking of grand unification symmetries. In addition,
the mass of the third-generation right-handed neutrino can be estimated in
seesaw scenarios. Even though the models are simplified and not intended to
account for all aspects of a final comprehensive SO(10) theory, they provide
nevertheless a valid base for identifying essential elements that can be
inferred on the fundamental high-scale theory from high-energy experiments.Comment: 26 pp LaTeX; version published in Phys. Rev.
Minimal Supersymmetric Inverse Seesaw: Neutrino masses, lepton flavour violation and LHC phenomenology
We study neutrino masses in the framework of the supersymmetric inverse
seesaw model. Different from the non-supersymmetric version a minimal
realization with just one pair of singlets is sufficient to explain all
neutrino data. We compute the neutrino mass matrix up to 1-loop order and show
how neutrino data can be described in terms of the model parameters. We then
calculate rates for lepton flavour violating (LFV) processes, such as , and chargino decays to singlet scalar neutrinos. The latter decays
are potentially observable at the LHC and show a characteristic decay pattern
dictated by the same parameters which generate the observed large neutrino
angles.Comment: 26 pages, 4 figures; added explanatory comments, final version for
publicatio
Neutrinoless double beta decay in left-right symmetric models with a universal seesaw mechanism
CP violation in sbottom decays
We study CP asymmetries in two-body decays of bottom squarks into charginos
and tops. These asymmetries probe the SUSY CP phases of the sbottom and the
chargino sector in the Minimal Supersymmetric Standard Model. We identify the
MSSM parameter space where the CP asymmetries are sizeable, and analyze the
feasibility of their observation at the LHC. As a result, potentially
detectable CP asymmetries in sbottom decays are found, which motivates further
detailed experimental studies for probing the SUSY CP phases.Comment: 29 pages, 7 figure
Higgs production in CP-violating supersymmetric cascade decays: probing the `open hole' at the Large Hadron Collider
A benchmark CP-violating supersymmetric scenario (known as 'CPX-scenario' in
the literature) 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 LEP data. We explore the parameter space with
cascade decay of third generation squarks and gluino with CP-violating decay
branching fractions. We propose a multi-channel analysis to probe this
parameter space some of which are background free at an integrated luminosity
of 5-10 fb. Specially, multi-lepton final states (3\l,\, 4\l and like
sign di-lepton) are almost background free and have reach for the
corresponding signals with very early data of LHC for both 14 TeV and 7 TeV
center of mass energy.Comment: 24 pages, 9 figures, references added as in the journal versio
LHC and lepton flavour violation phenomenology of a left-right extension of the MSSM
We study the phenomenology of a supersymmetric left-right model, assuming
minimal supergravity boundary conditions. Both left-right and (B-L) symmetries
are broken at an energy scale close to, but significantly below the GUT scale.
Neutrino data is explained via a seesaw mechanism. We calculate the RGEs for
superpotential and soft parameters complete at 2-loop order. At low energies
lepton flavour violation (LFV) and small, but potentially measurable mass
splittings in the charged scalar lepton sector appear, due to the RGE running.
Different from the supersymmetric 'pure seesaw' models, both, LFV and slepton
mass splittings, occur not only in the left- but also in the right slepton
sector. Especially, ratios of LFV slepton decays, such as Br()/Br() are sensitive to the
ratio of (B-L) and left-right symmetry breaking scales. Also the model predicts
a polarization asymmetry of the outgoing positrons in the decay , A ~ [0,1], which differs from the pure seesaw 'prediction' A=1$.
Observation of any of these signals allows to distinguish this model from any
of the three standard, pure (mSugra) seesaw setups.Comment: 43 pages, 17 figure
Constraint on the heavy sterile neutrino mixing angles in the SO(10) model with double see-saw mechanism
Constraints on the heavy sterile neutrino mixing angles are studied in the
framework of a minimal supersymmetric model with {\it double
see-saw mechanism}. A new singlet matter in addition to the right-handed
neutrinos is introduced to realize the double see-saw mechanism. The minimal
model gives an unambiguous Dirac neutrino mass matrix, which
enables us to predict the masses and the mixing angles in the enlarged neutrino mass matrix. Mixing angles between the light Majorana
neutrinos and the heavy sterile neutrinos are shown to be within the LEP
experimental bound on all ranges of the Majorana phases.Comment: 16 pages, 4 figures; the version to be published in Eur. Phys. J.
Relations among neutrino observables in the light of a large theta_13 angle
The recent T2K and MINOS indications for a "large" theta_13 neutrino mixing
angle can be accommodated in principle by an infinite number of Yukawa flavour
structures in the seesaw model. Without considering any explicit flavour
symmetry, there is an instructive exercise one can do: to determine the
simplest flavour structures which can account for the data with a minimum
number of parameters, simply assuming these parameters to be uncorrelated. This
approach points towards a limited number of simple structures which show the
minimum complexity a neutrino mass model must generally involve to account for
the data. These basic structures essentially lead to only 4 relations between
the neutrino observables. We emphasize that 2 of these relations, |sin
theta_13|=(tan theta_23/cos delta)*(1-tan theta_12)/(1+tan theta_12) and |sin
theta_13| = sin theta_12 R^1/4, with R= Delta m^2_21/Delta m^2_32, have several
distinctive properties. First, they hold not only with a minimum number of
parameters, but also for complete classes of more general models. Second, any
value of theta_13 within the T2K and MINOS ranges can be obtained from these
relations by taking into account small perturbations. Third, they turn out to
be the pivot relations of models with approximate conservation of lepton
number, which allow the seesaw interactions to induce observable flavour
violating processes, such as mu -> e gamma and tau -> mu gamma. Finally, in
specific cases of this kind, these structures have the rather unique property
to allow a full reconstruction of the seesaw Lagrangian from low energy data.Comment: 13 pages, 3 figure
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