1,704 research outputs found
Regenerating a Symmetry in Asymmetric Dark Matter
Asymmetric dark matter theories generically allow for mass terms that lead to
particle-antiparticle mixing. Over the age of the Universe, dark matter can
thus oscillate from a purely asymmetric configuration into a symmetric mix of
particles and antiparticles, allowing for pair-annihilation processes.
Additionally, requiring efficient depletion of the primordial thermal
(symmetric) component generically entails large annihilation rates. We show
that unless some symmetry completely forbids dark matter particle-antiparticle
mixing, asymmetric dark matter is effectively ruled out for a large range of
masses, for almost any oscillation time-scale shorter than the age of the
Universe.Comment: 5 pages, 2 figure
Neutrino Mass Matrices with a Texture Zero and a Vanishing Minor
We study the implications of the simultaneous existence of a texture zero and
a vanishing minor in the neutrino mass matrix. There are thirty six possible
texture structures of this type, twenty one of which reduce to two texture zero
cases which have, already, been extensively studied. Of the remaining fifteen
textures only six are allowed by the current data. We examine the
phenomenological implications of the allowed texture structures for Majorana
type CP-violating phases, 1-3 mixing angle and Dirac type CP-violating phase.
All these possible textures can be generated through the seesaw mechanism and
realized in the framework of discrete abelian flavor symmetry. We present the
symmetry realization of these texture structures.Comment: To appear in Phys. Rev.
On CP Violation in Minimal Renormalizable SUSY SO(10) and Beyond
We investigate the role of CP phases within the renormalizable SUSY SO(10)
GUT with one 10_H, one 126bar_H one 126_H and one 210_H Higgs representations
and type II seesaw dominating the neutrino mass matrix. This framework is non
trivially predictive in the fermionic sector and connects in a natural way the
GUT unification of b and tau Yukawa couplings with the bi-large mixing scenario
for neutrinos. On the other hand, existing numerical analysis claim that
consistency with quark and charged lepton data prevents the minimal setup from
reproducing the observed CP violation via the Cabibbo-Kobayashi-Maskawa (CKM)
matrix. We re-examine the issue and find by inspection of the fermion mass sum
rules and a detailed numerical scan that, even though the CKM phase takes
preferentially values in the second quadrant, the agreement of the minimal
model with the data is actually obtained in a non negligible fraction of the
parameter space. We then consider a recently proposed renormalizable extension
of the minimal model, obtained by adding one chiral 120-dimensional Higgs
supermultiplet. We show that within such a setup the CKM phase falls naturally
in the observed range. We emphazise the robust predictivity of both models here
considered for neutrino parameters that are in the reach of ongoing and future
experiments.Comment: 9 pages, 6 figures. Two refs added, discussion expanded. To appear on
Phys. Rev.
Minimal Seesaw as an Ultraviolet Insensitive Cure for the Problems of Anomaly Mediation
We show that an intermediate scale supersymmetric left-right seesaw scenario
with automatic R-parity conservation can cure the problem of tachyonic slepton
masses that arises when supersymmetry is broken by anomaly mediation, while
preserving ultraviolet insensitivity. The reason for this is the existence of
light B - L = 2 higgses with yukawa couplings to the charged leptons. We find
these theories to have distinct predictions compared to the usual mSUGRA and
gauge mediated models as well as the minimal AMSB models. Such predictions
include a condensed gaugino mass spectrum and possibly a correspondingly
condensed sfermion spectrum.Comment: 19 pages, 1 figur
Constraints on leptogenesis from a symmetry viewpoint
It is shown that type I seesaw models based on the standard model Lagrangian
extended with three heavy Majorana right-handed fields do not have leptogenesis
in leading order, if the symmetries of mass matrices are also the residual
symmetry of the Lagrangian. In particular, flavor models that lead to a
mass-independent leptonic mixing have a vanishing leptogenesis CP asymmetry.
Based on symmetry arguments, we prove that in these models the Dirac-neutrino
Yukawa coupling combinations relevant for leptogenesis are diagonal in the
physical basis where the charged leptons and heavy Majorana neutrinos are
diagonal.Comment: 5 pages; a few comments added; final version to appear in Phys. Rev.
Gauge and Yukawa mediated supersymmetry breaking in the triplet seesaw scenario
We propose a novel supersymmetric unified scenario of the triplet seesaw
mechanism where the exchange of the heavy triplets generates both neutrino
masses and soft supersymmetry breaking terms. Our framework is very predictive
since it relates neutrino mass parameters, lepton flavour violation in the
slepton sector, sparticle and Higgs spectra and electroweak symmetry breakdown.
The phenomenological viability and experimental signatures in lepton flavor
violating processes are discussed.Comment: 11 pages, 3 eps figs. Comments and references added. Final version to
be published in Phys. Rev. Let
Neutrino Mass Textures with Maximal CP Violation
We have found three types of neutrino mass textures, which give maximal
CP-violation as well as maximal atmospheric neutrino mixing. These textures are
described by six real mass parameters: one specified by two complex flavor
neutrino masses and two constrained ones and the others specified by three
complex flavor neutrino masses. In each texture, we calculate mixing angles and
masses as well as Majorana CP phases.Comment: 10 pages, RevTex, no figures, references updated, version to appear
in Phys. Rev.
Electroweak Symmetry Breaking and Proton Decay in SO(10) SUSY-GUT with TeV W_R
In a recent paper, we proposed a new class of supersymmetric SO(10) models
for neutrino masses where the TeV scale electroweak symmetry is SU(2)_L\times
SU(2)_R\times U(1)_{B-L} making the associated gauge bosons W_R and Z'
accessible at the Large Hadron Collider. We showed that there exists a domain
of Yukawa coupling parameters and symmetry breaking patterns which give an
excellent fit to all fermion masses including neutrinos. In this sequel, we
discuss an alternative Yukawa pattern which also gives good fermion mass fit
and then study the predictions of both models for proton lifetime. Consistency
with current experimental lower limits on proton life time require the squark
masses of first two generations to be larger than ~ 1.2 TeV. We also discuss
how one can have simultaneous breaking of both SU(2)_R\times U(1)_{B-L} and
standard electroweak symmetries via radiative corrections.Comment: 31 pages, 5 figures, 4 tables
Seesaw Right Handed Neutrino as the Sterile Neutrino for LSND
We show that a double seesaw framework for neutrino masses with
exchange symmetry can lead to one of the righthanded seesaw partners of the
light neutrinos being massless. This can play the role of a light sterile
neutrino, giving a model that explains the LSND results. We get a very
economical scheme, which makes it possible to predict the full
neutrino mass matrix if CP is conserved. Once CP violation is included, effect
of the LSND mass range sterile neutrino is to eliminate the lower bound on
neutrinoless double beta decay rate which exists for the three neutrino case
with inverted mass hierarchy. The same strategy can also be used to generate a
natural model for LSND, which is also equally predictive for the CP
conserving case in the limit of exact symmetry.Comment: 13 pages and one figure; model extended to 3+2 cas
- …