95 research outputs found
Testable constraint on near-tribimaximal neutrino mixing
General lowest order perturbations to hermitian squared mass matrices of
leptons are considered away from the tribimaximal (TBM) limit in which a weak
flavor basis with mass diagonal charged leptons is chosen. The three measurable
TBM deviants are expressed linearly in terms of perturbation induced
dimensionless coefficients appearing in the charged lepton and neutrino flavor
eigenstates. With unnatural cancellations assumed to be absent and the charged
lepton perturbation contributions to their flavor eigenstates argued to be
small, we analytically derive the following result. Within lowest order
perturbations, a deviation from maximal atmospheric neutrino mixing and the
amount of CP violation in neutrino oscillations cannot both be large (i.e.
-), posing the challenge of verification to forthcoming experiments
at the intensity frontier.Comment: published version: JHEP 02 (2015) 13
Kinetic mixing and symmetry breaking dependent interactions of the dark photon
We examine spontaneous symmetry breaking of a renormalisable U(1) x U(1)
gauge theory coupled to fermions when kinetic mixing is present. We do not
assume that the kinetic mixing parameter is small. A rotation plus scaling is
used to remove the mixing and put the gauge kinetic terms in the canonical
form. Fermion currents are also rotated in a non-orthogonal way by this basis
transformation. Through suitable redefinitions the interaction is cast into a
diagonal form. This framework, where mixing is absent, is used for subsequent
analysis. The symmetry breaking determines the fermionic current which couples
to the massless gauge boson. The strength of this coupling as well as the
couplings of the massive gauge boson are extracted. This formulation is used to
consider a gauged model for dark matter by identifying the massless gauge boson
with the photon and the massive state to its dark counterpart. Matching the
coupling of the residual symmetry with that of the photon sets a lower bound on
the kinetic mixing parameter. We present analytical formulae of the couplings
of the dark photon in this model and indicate some physics consequences.Comment: Latex, Nuclear Physics B (to appear
Gauge unification in 5-D SU(5) model with orbifold breaking of GUT symmetry
We consider a 5-dimensional SU(5) model wherein the symmetry is broken to the
4-dimensional Standard Model by compactification of the 5th dimension on an
S^1/(Z_2 \times Z^\prime_2) orbifold. We identify the members of all SU(5)
representations upto 75 which have zero modes. We examine how these light
scalars affect gauge coupling unification assuming a single intermediate scale
and present several acceptable solutions. The 5-D compactification scale
coincides with the unification scale of gauge couplings and is determined via
this renormalization group analysis. When SO(10) is considered as the GUT group
there are only two solutions, so long as a few low dimensional scalar
multiplets upto 126 are included.Comment: Latex, 1 eps figur
Neutrinoless Double Beta Decay with Negligible Neutrino Mass
If the electron neutrino has an effective nonzero Majorana mass, then
neutrinoless double beta decay will occur. However, the latter is possible also
with a negligible neutrino mass. We show how this may happen in a simple model
of scalar diquarks and dileptons. This possibility allows neutrino masses to be
small and hierarchical, without conflicting with the possible experimental
evidence of neutrinoless double beta decay.Comment: 9 pages, including 1 figur
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