1,231 research outputs found
Last CPT-Invariant Hope for LSND Neutrino Oscillations
It is shown that the 99% confidence limits from the analyses of the data of
cosmological and neutrino experiments imply a small marginally allowed region
in the space of the neutrino oscillation parameters of 3+1 four-neutrino mixing
schemes. This region can be confirmed or falsified by experiments in the near
future.Comment: 6 pages, added predictions for neutrinoless double beta decay and
tritium experiment
Lepton Numbers in the framework of Neutrino Mixing
In this short review we discuss the notion of lepton numbers. The strong
evidence in favor of neutrino oscillations obtained recently in the
Super-Kamiokande atmospheric neutrino experiment and in solar neutrino
experiments imply that the law of conservation of family lepton numbers L_e,
L_mu and L_tau is strongly violated. We consider the states of flavor neutrinos
nu_e, nu_mu and nu_tau and we discuss the evolution of these states in space
and time in the case of non-conservation of family lepton numbers due to the
mixing of light neutrinos. We discuss and compare different flavor neutrino
discovery experiments. We stress that experiments on the search for
nu_mu->nu_tau and nu_e->nu_tau oscillations demonstrated that the flavor
neutrino nu_tau is a new type of neutrino, different from nu_e and nu_mu. In
the case of neutrino mixing, the lepton number (only one) is connected with the
nature of massive neutrinos. Such conserved lepton number exist if massive
neutrinos are Dirac particles. We review possibilities to check in future
experiments whether the conserved lepton number exists.Comment: 20 page
Light Sterile Neutrinos and Inflationary Freedom
We perform a cosmological analysis in which we allow the primordial power
spectrum of scalar perturbations to assume a shape that is different from the
usual power-law predicted by the simplest models of cosmological inflation. We
parameterize the free primordial power spectrum with a "piecewise cubic Hermite
interpolating polynomial" (PCHIP). We consider a 3+1 neutrino mixing model with
a sterile neutrino having a mass at the eV scale, which can explain the
anomalies observed in short-baseline neutrino oscillation experiments. We find
that the freedom of the primordial power spectrum allows to reconcile the
cosmological data with a fully thermalized sterile neutrino in the early
Universe. Moreover, the cosmological analysis gives us some information on the
shape of the primordial power spectrum, which presents a feature around the
wavenumber .Comment: 19 pages; corrected Fig.4 and added Ref.[35
Light Sterile Neutrinos in Cosmology and Short-Baseline Oscillation Experiments
We analyze the most recent cosmological data, including Planck, taking into
account the possible existence of a sterile neutrino with a mass at the eV
scale indicated by short-baseline neutrino oscillations data in the 3+1
framework. We show that the contribution of local measurements of the Hubble
constant induces an increase of the value of the effective number of
relativistic degrees of freedom above the Standard Model value, giving an
indication in favor of the existence of sterile neutrinos and their
contribution to dark radiation. Furthermore, the measurements of the local
galaxy cluster mass distribution favor the existence of sterile neutrinos with
eV-scale masses, in agreement with short-baseline neutrino oscillations data.
In this case there is no tension between cosmological and short-baseline
neutrino oscillations data, but the contribution of the sterile neutrino to the
effective number of relativistic degrees of freedom is likely to be smaller
than one. Considering the Dodelson-Widrow and thermal models for the
statistical cosmological distribution of sterile neutrinos, we found that in
the Dodelson-Widrow model there is a slightly better compatibility between
cosmological and short-baseline neutrino oscillations data and the required
suppression of the production of sterile neutrinos in the early Universe is
slightly smaller.Comment: 12 pages; final version published in JHEP 1311 (2013) 21
Light sterile neutrinos and inflationary freedom
We perform a cosmological analysis in which we allow the primordial power spectrum of scalar perturbations to assume a shape that is different from the usual power-law predicted by the simplest models of cosmological inflation. We parameterize the free primordial power spectrum with a ``piecewise cubic Hermite interpolating polynomial'' (PCHIP). We consider a 3+1 neutrino mixing model with a sterile neutrino having a mass at the eV scale, which can explain the anomalies observed in short-baseline neutrino oscillation experiments. We find that the freedom of the primordial power spectrum allows to reconcile the cosmological data with a fully thermalized sterile neutrino in the early Universe. Moreover, the cosmological analysis gives us some information on the shape of the primordial power spectrum, which presents a feature around the wavenumber k=0.002 Mpc 121
Dirac Spinors and Flavor Oscillations
In the standard treatment of particle oscillations the mass eigenstates are
implicitly assumed to be scalars and, consequently, the spinorial form of
neutrino wave functions is not included in the calculations. To analyze this
additional effect, we discuss the oscillation probability formula obtained by
using the Dirac equation as evolution equation for the neutrino mass
eigenstates. The initial localization of the spinor state also implies an
interference between positive and negative energy components of mass eigenstate
wave packets which modifies the standard oscillation probability.Comment: 14 pages, 1 figure, AMS-Te
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