909 research outputs found
Large - Oscillations from High-Dimensional Lepton Number Violating Operator
It is usually believed that the observation of the neutrino-antineutrino
(-) oscillations is almost impossible since the oscillation
probabilities are expected to be greatly suppressed by the square of tiny ratio
of neutrino masses to energies. Such an argument is applicable to most models
for neutrino mass generation based on the Weinberg operator, including the
seesaw models. However, in the present paper, we shall give a counterexample to
this argument, and show that large - oscillation probabilities
can be obtained in a class of models in which both neutrino masses and
neutrinoless double beta () decays are induced by the
high-dimensional lepton number violating operator with and representing the first two
generations of quarks. In particular, we find that the predicted
decay rates have already placed interesting constraints on the
oscillation. Moreover, we provide an
UV-complete model to realize this scenario, in which a dark matter candidate
naturally appears due to the new symmetry.Comment: 21 pages, 6 figure
Flavors and Phases in Unparticle Physics
Inspired by the recent Georgi's unparticle proposal, we study the flavor
structures of the standard model (SM) particles when they couple to
unparticles. At a very high energy scale, we introduce \BZ charges for the SM
particles, which are universal for each generation and allow \BZ fields to
distinguish flavor generations. At the \Lambda_{\UP} scale, \BZ operators
and charges are matched onto unparticle operators and charges, respectively. In
this scenario, we find that tree flavor changing neutral currents (FCNCs) can
be induced by the rediagonalizations of the SM fermions. As an illustration, we
employ the Fritzsch ansatz to the SM fermion mass matrices and we find that the
FCNC effects could be simplified to be associated with the mass ratios denoted
by , where is the mass of the heaviest
particle in each type of fermion generations and are the flavor indices.
In addition, we show that there is no new CP violating phase beside the unique
one in the CKM matrix. We use as examples to
display the new FCNC effects. In particular, we demonstrate that the direct CP
asymmetries in the decays can be due to the peculiar CP conserving
phase in the unparticle propagator.Comment: 1+14 pages, 2 figures, version to appear in Phys. Lett.
- …