4,510 research outputs found

### KATRIN Sensitivity to Sterile Neutrino Mass in the Shadow of Lightest Neutrino Mass

The presence of light sterile neutrinos would strongly modify the energy
spectrum of the Tritium \beta-electrons. We perform an analysis of the KATRIN
experiment's sensitivity by scanning almost all the allowed region of neutrino
mass-squared difference and mixing angles of the 3+1 scenario. We consider the
effect of the unknown absolute mass scale of active neutrinos on the
sensitivity of KATRIN to the sterile neutrino mass. We show that after 3 years
of data-taking, the KATRIN experiment can be sensitive to mixing angles as
small as sin^2 (2\theta_s) ~ 10^-2. Particularly we show that for small mixing
angles, sin^2 (2\theta_s) < 0.1, the KATRIN experiment can gives the strongest
limit on active-sterile mass-squared difference.Comment: 4 pages, 2 figures, matches the published versio

### A torsional completion of gravity for Dirac matter fields and its applications to neutrino oscillations

In this paper, we consider the torsional completion of gravitation for an
underlying background filled with Dirac fields, applying it to the problem of
neutrino oscillations: we discuss the effects of the induced torsional
interactions as corrections to the neutrino oscillation mechanism.Comment: 4 page

### Lepton flavour violation in The Little Higgs model

Little Higgs models with T-parity have a new source of lepton flavour
violation. In this paper we consider the anomalous magnetic moment of the muon
\gmtwo and the lepton flavour violating decays \mutoeg and \tautomug in Little
Higgs model with T-parity \cite{Goyal:2006vq}. Our results shows that present
experimental constraints of \mutoeg is much more useful to constrain the new
sources of flavour violation which are present in T-parity models.Comment: LaTeX file with 13 eps figures (included

### Testability of Type I Seesaw at the CERN LHC: Revealing the Existence of the B-L Symmetry

We study the possibility to test the Type I seesaw mechanism for neutrino
masses at the CERN Large Hadron Collider. The inclusion of three generations of
right-handed neutrinos (N_i) provides an attractive option of gauging the B-L
accidental symmetry in the Standard Model (as well as an extended symmetry
X=Y-5(B-L)/4). The production mechanisms for the right-handed neutrinos through
the Z' gauge boson in the U(1)_{B-L} and U(1)_X extensions of the Standard
Model are studied. We discuss the flavor combinations of the charged leptons
from the decays of N_i in the Delta L=2 channels. We find that the clean
channels with dilepton plus jets and possible secondary vertices of the N decay
could provide conclusive signals at the LHC in connection with the hierarchical
pattern of the light neutrino masses and mixing properties within the Type I
seesaw mechanism.Comment: 40 pages, 27 figures, several modifications made and accepted for
publication in Phys. Rev.

### Relations between Neutrino and Charged Fermion Masses

We find an intriguing relation between neutrino and charged fermion masses,
$|m_{\nu_3^{}}^2- m_{\nu_1^{}}^2| : (m_{\nu_2^{}}^2- m_{\nu_1^{}}^2):: V_{tb}^4
m_\tau^2 m_b^2/m_t^2 : V_{cs}^4 m_\mu^2 m_s^2/m_c^2$. We further indicate this
relation can be predicted by a left-right symmetric model.Comment: 4 pages, 1 figure. Model is slightly corrected. Title is changed.
Journal versio

### Neutrino Mixing and Quark-Lepton Complementarity

As a result of identification of the solution to the solar neutrino problem,
a rather precise relation theta_{sun} + theta_C = pi/4 between the leptonic 1-2
mixing angle theta_{sun} and the Cabibbo angle has emerged. It would mean that
the lepton and the quark mixing angles add up to the maximal, suggesting a deep
structure by which quarks and leptons are interrelated. We refer the relation
``quark-lepton complementarity'' (QLC) in this paper. We formulate general
conditions under which the QLC relation is realized. We then present several
scenarios which lead to the relation and elaborate on phenomenological
consequences which can be tested by the future experiments. We also discuss
implications of the QLC relation for the quark-lepton symmetry and the
mechanism of neutrino mass generation.Comment: 22 pages, version to be published in Phys. Rev.

### Lepton number violating four-body tau lepton decays

We study the four-body tau^+- -> nu_tau l^+- l^+- X^-+ decays where l=e or mu
and X=pi, K, rho and K^* mesons. These decay processes violate the total lepton
number (|Delta L|=2) and can be induced by the exchange of Majorana neutrinos.
We consider an scenario where these decays are dominated by the exchange of
only one heavy neutrino which produces an enhancement of the decay amplitude
via the resonant mechanism. Searches for these novel decay channels with
branching fractions sensitivities of (10^-7) can provide constraints on the
parameter space of the Majorana neutrinos which are stronger than the ones
obtained from Delta L=2 decays of charged pseudoscalar mesons.Comment: REVTeX, 14 pages, 6 figures, four references added. Version accepted
for publication in PR

### Viewing Lepton Mixing through the Cabibbo Haze

We explore the hypothesis that the Cabibbo angle is an expansion parameter
for lepton as well as quark mixing. Cabibbo effects are deviations from zero
mixing for the quarks but are deviations from unknown mixings for the leptons,
such that lepton mixing is veiled by a Cabibbo haze. We present a systematic
classification of parametrizations and catalog the leading order Cabibbo
effects. We find that the size of the CHOOZ angle is not always correlated with
the observability of CP violation. This phenomenological approach has practical
merit both as a method for organizing top-down flavor models and as a guideline
for planning future experiments.Comment: References added, minor typos fixe

### On entanglement in neutrino mixing and oscillations

We report on recent results about entanglement in the context of particle
mixing and oscillations. We study in detail single-particle entanglement
arising in two-flavor neutrino mixing. The analysis is performed first in the
context of Quantum Mechanics, and then for the case of Quantum Field Theory.Comment: 14 pages, 2 figures. Presented at "Symmetries in Science Symposium -
Bregenz 2009"

### Testing Supersymmetry with Lepton Flavor Violating tau and mu decays

In this work the following lepton flavor violating $\tau$ and $\mu$ decays
are studied: $\tau^- \to \mu^- \mu^- \mu^+$, $\tau^- \to e^- e^- e^+$, $\mu^-
\to e^- e^- e^+$, $\tau^- \to \mu^- \gamma$, $\tau^- \to e^- \gamma$ and $\mu^-
\to e^- \gamma$. We work in a supersymmetric scenario consisting of the minimal
supersymmetric standard model particle content, extended by the addition of
three heavy right handed Majorana neutrinos and their supersymmetric partners,
and where the generation of neutrino masses is done via the seesaw mechanism.
Within this context, a significant lepton flavor mixing is generated in the
slepton sector due to the Yukawa neutrino couplings, which is transmited from
the high to the low energies via the renormalization group equations. This
slepton mixing then generates via loops of supersymmetric particles significant
contributions to the rates of $l_j \to 3 l_i$ and the correlated $l_j \to l_i
\gamma$ decays. We analize here in full detail these rates in terms of the
relevant input parameters, which are the usual minimal supergravity parameters
and the seesaw parameters. For the $l_j \to 3 l_i$ decays, a full one-loop
analytical computation of all the contributing supersymmetric loops is
presented. This completes and corrects previous computations in the literature.
In the numerical analysis compatibility with the most recent experimental upper
bounds on all these $\tau$ and $\mu$ decays, with the neutrino data, and with
the present lower bounds on the supersymmetric particle masses are required.
Two typical scenarios with degenerate and hierarchical heavy neutrinos are
considered. We will show here that the minimal supergravity and seesaw
parameters do get important restrictions from these $\tau$ and $\mu$ decays in
the hierarchical neutrino case.Comment: Version to appear in Physical Review

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