221 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
High-energy neutrino conversion into electron-W pair in magnetic field and its contribution to neutrino absorption
We calculate the conversion rate of high-energy neutrinos propagating in
constant magnetic field into an electron-W pair (nu -> W + e) from the
imaginary part of the neutrino self-energy. Using the exact propagators in
constant magnetic field, the neutrino self-energy has been calculated to all
order in the field within the Weinberg-Salam model. We obtain a compact formula
in the limit of B << Bcr = m^2/e. We find that above the process threshold Eth
\~ 2.2 10^16 (Bcr / B) eV this contribution to the absorption of neutrinos
yields an asymptotic absorption length ~ 1.1 (Bcr / B)^2 (10^{16} eV / E)
meters.Comment: 10 pages in RevTeX, 2 figures; published version: two typos
corrected, one reference adde
Photon-Neutrino Interactions in Magnetic Field through Neutrino Magnetic Moment
We study the neutrino-photon processes like in
the presence of uniform external magnetic field for the case when neutrinos can
couple to the electromagnetic field directly through their dipole magnetic
moment and obtain the stellar energy loss. The process would be of special
relevance in astrophysical situations where standard left-handed neutrinos are
trapped and the right handed neutrinos produced through the spin flip
interaction induced by neutrino magnetic moment alone can freely stream out.Comment: LaTex2e file, 9 page
Neutrino emission via the plasma process in a magnetized plasma
Neutrino emission via the plasma process using the vertex formalism for QED
in a strongly magnetized plasma is considered. A new vertex function is
introduced to include the axial vector part of the weak interaction. Our
results are compared with previous calculations, and the effect of the axial
vector coupling on neutrino emission is discussed. The contribution from the
axial vector coupling can be of the same order as or greater than the vector
vector coupling under certain plasma conditions.Comment: 20 pages, 3 figure
The Amplitude in an External Homogeneous Electromagnetic Field
Neutrino-photon interactions in the presence of an external homogeneous
constant electromagnetic field are studied. The amplitude is
calculated in an electromagnetic field of the general type, when the two field
invariants are nonzero.Comment: 7 pages, 1 figur
Earthquake Forecast via Neutrino Tomography
We discuss the possibility of forecasting earthquakes by means of
(anti)neutrino tomography. Antineutrinos emitted from reactors are used as a
probe. As the antineutrinos traverse through a region prone to earthquakes,
observable variations in the matter effect on the antineutrino oscillation
would provide a tomography of the vicinity of the region. In this preliminary
work, we adopt a simplified model for the geometrical profile and matter
density in a fault zone. We calculate the survival probability of electron
antineutrinos for cases without and with an anomalous accumulation of electrons
which can be considered as a clear signal of the coming earthquake, at the
geological region with a fault zone, and find that the variation may reach as
much as 3% for emitted from a reactor. The case for a beam
from a neutrino factory is also investigated, and it is noted that, because of
the typically high energy associated with such neutrinos, the oscillation
length is too large and the resultant variation is not practically observable.
Our conclusion is that with the present reactor facilities and detection
techniques, it is still a difficult task to make an earthquake forecast using
such a scheme, though it seems to be possible from a theoretical point of view
while ignoring some uncertainties. However, with the development of the
geology, especially the knowledge about the fault zone, and with the
improvement of the detection techniques, etc., there is hope that a medium-term
earthquake forecast would be feasible.Comment: 6 pages, 4 figures, 1 tabl
Light Sterile Neutrino from extra dimensions and Four-Neutrino Solutions to Neutrino Anomalies
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. It applies the idea that extra compact
dimensions, probed only by gravity and possibly gauge-singlet fields, can lower
the fundamental scales such as the Planck, string or unification scales. Our
fourth light neutrino ( for sterile) is identified with the zero
mode of the Kaluza-Klein states. To first approximation \nu_sterile combines
with the nu_mu in order to form a Dirac neutrino with mass in the eV range
leaving the other two neutrinos massless. The smallness of this mass scale
(suitable for LSND and Hot Dark Matter) arises without appealing neither to a
see-saw mechanism nor to a radiative mechanism, but from the volume factor
associated with the canonical normalization of the wave-function of the bulk
field in the compactified dimensions. % On the other hand the splitting between
\nm and \nu_sterile (atmospheric scale) as well as the mass of the two other
neutrinos (solar mass scale) arise from the violation of the fermion number on
distant branes. We also discuss alternative scenarios involving
flavour-changing interactions. In one of them \ne can be in the electron-volt
range and therefore be probed in beta decay studies.Comment: 12 pages, latex, no figures, title changed, final version to be
published in Phys Rev
Neutrino anomalies and large extra dimensions
Theories with large extra dimensions can generate small neutrino masses when
the standard model neutrinos are coupled to singlet fermions propagating in
higher dimensions. The couplings can also generate mass splittings and mixings
among the flavour neutrinos in the brane. We systematically study the minimal
scenario involving only one singlet bulk fermion coupling weakly to the flavour
neutrinos. We explore the neutrino mass structures in the brane that can
potentially account for the atmospheric, solar and LSND anomalies
simultaneously in a natural way. We demonstrate that in the absence of a priori
mixings among the SM neutrinos, it is not possible to reconcile all these
anomalies. The presence of some structure in the mass matrix of the SM
neutrinos can solve this problem. This is exemplified by the Zee model, which
when embedded in extra dimensions in a minimal way can account for all the
neutrino anomalies.Comment: 23 Revtex pages with 2 eps figure
Bulk neutrinos and core collapse supernovae
We discuss the phenomenology of neutrino mixing with bulk fermions in the
context of supernova physics. The constraints on the parameter space following
from the usual energy loss argument can be relaxed by four orders of magnitude
due to a feedback mechanism that takes place in a broad region of the parameter
space. Such a mechanism also affects the protoneutron star evolution through a
non trivial interplay with neutrino diffusion. The consistency with the SN
1987A signal is discussed, as well as the implications for deleptonization,
cooling, composition of the neutrino flux and the delayed explosion scenario.Comment: 23 pages, 5 eps figures; v2: minor comments and references added,
version to appear on Phys.Rev.
Ultraviolet sensitivity of rare decays in nonuniversal extra dimensional models
We consider a nonuniversal five dimensional model in which fermions are
localised on a four dimensional brane, while gauge bosons and a scalar doublet
can travel in the bulk. As a result of KK number non-conservation at the
brane-bulk intersection, the ultraviolet divergence does not cancel out in some
physical observables. For example, the decay amplitude is
linearly divergent, while -- mixing amplitude is log divergent. We
attempt to identify the exact source of this nonrenormalizability. We compare
and contrast our results with those obtained in the universal five dimensional
model where all particles travel in the extra dimension.Comment: Latex, 11 pages, uses axodraw.st
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