262 research outputs found
Constraining neutrino magnetic moment with solar and reactor neutrino data
We use solar neutrino data to derive stringent bounds on Majorana neutrino
transition moments (TMs). Such moments, if present, would contribute to the
neutrino-electron scattering cross section and hence alter the signal observed
in Super-Kamiokande. Using the latest solar neutrino data, combined with the
results of the reactor experiment KamLAND, we perform a simultaneous fit of the
oscillation parameters and TMs. Furthermore, we include data from the reactor
experiments Rovno, TEXONO and MUNU in our analysis, improving significantly the
current constraints on TMs. A comparison with previous works shows that our
bounds are the strongest and most general results presented up to now. Finally,
we perform a simulation of the future Borexino experiment and show that it will
improve the bounds from today's data by order of magnitude.Comment: 12 pages, LaTeX file using JHEP3, 4 figures and 1 table included.
Talk presented at the International Workshop on Astroparticle and High Energy
Physics (AHEP-2003), Valencia, Spain, 14-18 October 200
Status of three-neutrino oscillations after the SNO-salt data
We perform a global analysis of neutrino oscillation data in the framework of
three neutrinos, including the recent improved measurement of the neutral
current events at SNO. In addition to all current solar neutrino data we take
into account the reactor neutrino data from KamLAND and CHOOZ, the atmospheric
neutrino data from Super-Kamiokande and MACRO, as well as the first spectral
data from the K2K long baseline accelerator experiment. The up-to-date best fit
values and allowed ranges of the three-flavour oscillation parameters are
determined from these data. Furthermore, we discuss in detail the status of the
small parameters alpha = Delta_m^2_Sol / Delta_m^2_Atm and sin^2(theta_13),
which fix the possible strength of CP violating effects in neutrino
oscillations.Comment: 16 pages, LaTeX file using RevTEX4, 10 figures and 1 table included.
The conclusions reached in version 1 regarding the restriction on
sin^2(theta_13) are now corrected, the solar bound is weaker than that from
reactors even after the inclusion of the SNO salt data. In addition the full
data set has now been reanalized using the pull method instead of the
standard chi-square approach. A few references have also been adde
Status of neutrino oscillations 2018: first hint for normal mass ordering and improved CP sensitivity
We present a new global fit of neutrino oscillation parameters within the
simplest three-neutrino picture, including new data which appeared since our
previous analysis~\cite{Forero:2014bxa}. In this update we include new
long-baseline neutrino data involving the antineutrino channel in T2K, as well
as new data in the neutrino channel, data from NOA, as well as new reactor
data, such as the Daya Bay 1230 days electron antineutrino disappearance
spectrum data and the 1500 live days prompt spectrum from RENO, as well as new
Double Chooz data. We also include atmospheric neutrino data from the IceCube
DeepCore and ANTARES neutrino telescopes and from Super-Kamiokande. Finally, we
also update our solar oscillation analysis by including the 2055-day day/night
spectrum from the fourth phase of the Super-Kamiokande experiment. With the new
data we find a preference for the atmospheric angle in the upper octant for
both neutrino mass orderings, with maximal mixing allowed at for normal (inverted) ordering. We also obtain a strong
preference for values of the CP phase in the range ,
excluding values close to at more than 4. More remarkably, our
global analysis shows for the first time hints in favour of the normal mass
ordering over the inverted one at more than 3. We discuss in detail the
origin of the mass ordering, CP violation and octant sensitivities, analyzing
the interplay among the different neutrino data samples.Comment: Updated neutrino oscillation analysis using the most recent results
from T2K, NOA, RENO and Super-Kamiokande. 17 pages, 8 figures, 1 tabl
Non-standard neutrino oscillations: perspective from unitarity triangles
We formulate an alternative approach based on unitarity triangles to describe
neutrino oscillations in presence of non-standard interactions (NSI). Using
perturbation theory, we derive the expression for the oscillation probability
in case of NSI and cast it in terms of the three independent parameters of the
leptonic unitarity triangle (LUT). The form invariance of the probability
expression (even in presence of new physics scenario as long as the mixing
matrix is unitary) facilitates a neat geometric view of neutrino oscillations
in terms of LUT. We examine the regime of validity of perturbative expansions
in the NSI case and make comparisons with approximate expressions existing in
literature. We uncover some interesting dependencies on NSI terms while
studying the evolution of LUT parameters and the Jarlskog invariant.
Interestingly, the geometric approach based on LUT allows us to express the
oscillation probabilities for a given pair of neutrino flavours in terms of
only three (and not four) degrees of freedom which are related to the geometric
properties (sides and angles) of the triangle. Moreover, the LUT parameters are
invariant under rephasing transformations and independent of the
parameterization adopted.Comment: 21 pages, 7 figure
Probing Low Energy Neutrino Backgrounds with Neutrino Capture on Beta Decaying Nuclei
We study the interaction of low energy neutrinos on nuclei that spontaneously
undergo beta decay showing that the product of the cross section times neutrino
velocity takes values as high as 10^{-42} cm^2 c for some specific nuclei that
decay via allowed transitions. The absence of energy threshold and the value of
the cross section single out these processes as a promising though very
demanding approach for future experiments aimed at a direct detection of low
energy neutrino backgrounds such as the cosmological relic neutrinos.Comment: Includes a discussion of local relic neutrino density effect on
neutrino capture rate. Accepted for publication in JCA
Sterile neutrinos with altered dispersion relations revisited
In this paper we investigate neutrino oscillations with altered dispersion
relations in the presence of sterile neutrinos. Modified dispersion relations
represent an agnostic way to parameterize new physics. Models of this type have
been suggested to explain global neutrino oscillation data, including
deviations from the standard three-neutrino paradigm as observed by a few
experiments. We show that, unfortunately, in this type of models new tensions
arise turning them incompatible with global data.Comment: 22 pages, 7 figures, 2 tables. Version 2, matches published versio
Solar neutrino-electron scattering as background limitation for double beta decay
The background on double beta decay searches due to elastic electron
scattering of solar neutrinos of all double beta emitters with Q-value larger
than 2 MeV is calculated, taking into account survival probability and flux
uncertainties of solar neutrinos. This work determines the background level to
be [1-2]E-7 counts /keV/kg/yr, depending on the precise Q-value of the double
beta emitter. It is also shown that the background level increases dramatically
if going to lower Q-values. Furthermore, studies are done for various detector
systems under consideration for next generation experiments. It was found that
experiments based on loaded liquid scintillator have to expect a higher
background. Within the given nuclear matrix element uncertainties any approach
exploring the normal hierarchy has to face this irreducible background, which
is a limitation on the minimal achievable background for purely calorimetric
approaches. Large scale liquid scintillator experiments might encounter this
problem already while exploring the inverted hierarchy. Potential caveats by
using more sophisticated experimental setups are also discussed
Neutrino-less Double Beta Decay and Particle Physics
We review the particle physics aspects of neutrino-less double beta decay.
This process can be mediated by light massive Majorana neutrinos (standard
interpretation) or by something else (non-standard interpretations). The
physics potential of both interpretations is summarized and the consequences of
future measurements or improved limits on the half-life of neutrino-less double
beta decay are discussed. We try to cover all proposed alternative realizations
of the decay, including light sterile neutrinos, supersymmetric or left-right
symmetric theories, Majorons, and other exotic possibilities. Ways to
distinguish the mechanisms from one another are discussed. Experimental and
nuclear physics aspects are also briefly touched, alternative processes to
double beta decay are discussed, and an extensive list of references is
provided.Comment: 96 pages, 38 figures. Published versio
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