409 research outputs found
Transition Radiation by Standard Model Neutrinos at an Interface
We discuss the transition radiation process at an
interface of two media. The medium fulfills the dual purpose of inducing an
effective neutrino-photon vertex and of modifying the photon dispersion
relation. The transition radiation occurs when at least one of those quantities
have different values in different media. We present a result for the
probability of the transition radiation which is both accurate and analytic.
For MeV neutrino crossing polyethylene-vacuum interface the
transition radiation probability is about and the energy intensity
(deposition) is about eV. At the surface of the neutron stars the
transition radiation probability may be . Our result on three
orders of magnitude is larger than the results of previous calculations.}Comment: invited talk, to appear in the proceedings of the XLVIth Rencontres
de Moriond EW 201
Phenomenology of neutrino physics in the Kaluza-Klein theories of low scale gravity
We discuss the phenomenological consequences of theories which describe
sterile neutrinos in large extra dimensions. We show that the Kaluza-Klein
tower of the singlet neutrinos, albeit tiny individual contribution in
electroweak processes, act cumulatively, giving rise to non-universality of the
weak interactions of the light neutrinos and to flavour-violating radiative
processes. Owing to these non-decoupling effects of th Kaluza--Klein neutrinos,
we derive strong constraints on the parameters of the theory that originates
from the non-observation of flavour-violating and universality-breaking
phenomena. In this theory we propose a four-neutrino model which can reconcile
the existing data coming from underground experiments in terms of neutrino
oscillations, together with the hint from the LSND experiment and a possible
neutrino contribution to the hot dark matter of the Universe.Comment: 5 pages, Talk given at the EuroConference on Frontiers in Particle
Astrophysics and Cosmology, San Feliu de Guixols, Spain, 30 September - 5
October, 200
Cumulative Non-Decoupling Effects of Kaluza-Klein Neutrinos in Electroweak Processes
In Kaluza-Klein theories of low-scale quantum gravity, gravitons and
isosinglet neutrinos may propagate in a higher-dimensional space with large
compact dimensions, whereas all particles of the Standard Model are confined on
a (1+3)-dimensional subspace. After compactification of the extra dimensions,
the resulting Yukawa couplings of the Kaluza-Klein neutrinos to the lepton
doublets become naturally very suppressed by a higher-dimensional volume
factor, in agreement with phenomenological observations. We show that one-loop
effects induced by Kaluza-Klein neutrinos, albeit tiny individually, act
cumulatively in electroweak processes, giving rise to a non-decoupling
behaviour for large values of the higher-dimensional Yukawa couplings. Owing to
the non-decoupling effects of Kaluza-Klein neutrinos, we can derive stronger
constraints on the parameters of the theory that originate from the
non-observation of flavour-violating and universality-breaking phenomena, which
involve the W and Z bosons, and the e, and leptons.Comment: 31 pages, LaTeX, to appear in Physical Review
Transition Radiation by Neutrinos
We calculate the transition radiation process at an
interface of two media. The neutrinos are taken to be with only standard-model
couplings. The medium fulfills the dual purpose of inducing an effective
neutrino-photon vertex and of modifying the photon dispersion relation. The
transition radiation occurs when at least one of those quantities have
different values in different media. The neutrino mass is ignored due to its
negligible contribution. We present a result for the probability of the
transition radiation which is both accurate and analytic. For MeV
neutrino crossing polyethylene-vacuum interface the transition radiation
probability is about and the energy intensity is about
eV. At the surface of the neutron stars the transition radiation probability
may be . Our result on three orders of magnitude is larger than
the results of previous calculations
Degenerate Neutrinos and CP Violation
We have studied mixing and masses of three left handed Majorana neutrinos in
the model, which assumes exactly degenerate neutrino masses at some "neutrino
unification" scale. Such a simple theoretical ansatz naturally leads to
quasidegenerate neutrinos. The neutrino mass splittings induced by
renormalization effects. In the model we found that the parameters of the
neutrino physics (neutrino mass spectrum, mixing angles and CP violation
phases) are strongly intercorrelated to each other. From these correlations we
got strong bounds on the parameters which could be checked in the oscillation
experiments.Comment: 5 pages, latex, presented at CAPP200
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