14,715 research outputs found
Invisible decays of ultra-high energy neutrinos
Gamma-ray bursts (GRBs) are expected to provide a source of ultra high energy
cosmic rays, accompanied with potentially detectable neutrinos at neutrino
telescopes. Recently, IceCube has set an upper bound on this neutrino flux well
below theoretical expectation. We investigate whether this mismatch between
expectation and observation can be due to neutrino decay. We demosntrate the
phenomenological consistency and theoretical plausibility of the neutrino decay
hypothesis. A potential implication is the observability of majoron-emitting
neutrinoless double beta decay.Comment: 11 pages, 3 figures. To appear in Frontiers High Energy Physic
Global constraints on muon-neutrino non-standard interactions
The search for new interactions of neutrinos beyond those of the Standard
Model may help to elucidate the mechanism responsible for neutrino masses. Here
we combine existing accelerator neutrino data with restrictions coming from a
recent atmospheric neutrino data analysis in order to lift parameter
degeneracies and improve limits on new interactions of muon neutrinos with
quarks. In particular we re-consider the results of the NuTeV experiment in
view of a new evaluation of its systematic uncertainties. We find that,
although constraints for muon neutrinos are better than those applicable to tau
or electron neutrinos, they lie at the few level, not as
strong as previously believed. We briefly discuss prospects for further
improvement.Comment: 10 pages, 5 figures, 2 table
Calculable inverse-seesaw neutrino masses in supersymmetry
We provide a scenario where naturally small and calculable neutrino masses
arise from a supersymmetry breaking renormalization-group-induced vacuum
expectation value. We adopt a minimal supergravity scenario without ad hoc
supersymmetric mass parameters. The lightest supersymmetric particle can be an
isosinglet scalar neutrino state, potentially viable as WIMP dark matter
through its Higgs new boson coupling. The scenario leads to a plethora of new
phenomenological implications at accelerators including the Large Hadron
Collider.Comment: LaTeX, 5 pages, 4 figures. Comments and references added. Final
version to appear in PR
Effective penetration length and interstitial vortex pinning in superconducting films with regular arrays of defects
In order to compare magnetic and non-magnetic pinning we have nanostructured
two superconducting films with regular arrays of pinning centers: Cu
(non-magnetic) dots in one case, and Py (magnetic) dots in the other. For low
applied magnetic fields, when all the vortices are pinned in the artificial
inclusions, magnetic dots prove to be better pinning centers, as has been
generally accepted. Unexpectedly, when the magnetic field is increased and
interstitial vortices appear, the results are very different: we show how the
stray field generated by the magnetic dots can produce an effective reduction
of the penetration length. This results in strong consequences in the transport
properties, which, depending on the dot separation, can lead to an enhancement
or worsening of the transport characteristics. Therefore, the election of the
magnetic or non-magnetic character of the pinning sites for an effective
reduction of dissipation will depend on the range of the applied magnetic
field.Comment: 10 pages, 3 figure
Probing neutrino transition magnetic moments with coherent elastic neutrino-nucleus scattering
We explore the potential of current and next generation of coherent elastic
neutrino-nucleus scattering (CENS) experiments in probing neutrino
electromagnetic interactions. On the basis of a thorough statistical analysis,
we determine the sensitivities on each component of the Majorana neutrino
transition magnetic moment (TMM), , that
follow from low-energy neutrino-nucleus experiments. We derive the sensitivity
to neutrino TMM from the first CENS measurement by the COHERENT
experiment, at the Spallation Neutron Source. We also present results for the
next phases of COHERENT using HPGe, LAr and NaI[Tl] detectors and for reactor
neutrino experiments such as CONUS, CONNIE, MINER, TEXONO and RED100. The role
of the CP violating phases in each case is also briefly discussed. We conclude
that future CENS experiments with low-threshold capabilities can improve
current TMM limits obtained from Borexino data.Comment: 25 pages, 8 figures, 2 tables, analysis updated; conclusions
unchanged; references added; matches published versio
On the description of non-unitary neutrino mixing
Neutrino oscillations are well established and the relevant parameters
determined with good precision, except for the CP phase, in terms of a unitary
lepton mixing matrix. Seesaw extensions of the Standard Model predict unitarity
deviations due to the admixture of heavy isosinglet neutrinos. We provide a
complete description of the unitarity and universality deviations in the light
neutrino sector. Neutrino oscillation experiments involving electron or muon
neutrinos and anti-neutrinos are fully described in terms of just three new
real parameters and a new CP phase, in addition to the ones describing
oscillations with unitary mixing. Using this formalism we describe the
implications of non-unitarity for neutrino oscillations and summarize the
model-independent constraints on heavy neutrino couplings that arise from
current experiments.Comment: 28 pages, 8 figures, typos corrected, modified bounds on
non-unitarity parameters, new figs 3 and
Inverse tri-bimaximal type-III seesaw and lepton flavor violation
We present a type-III version of inverse seesaw or, equivalently an inverse
version of type-III seesaw. Naturally small neutrino masses arise at low-scale
from the exchange of neutral fermions transforming as hyperchargeless SU(2)
triplets. In order to implement tri-bimaximal lepton mixing we supplement the
minimal SU(3)xSU(2)xU(1) gauge symmetry with an A4-based flavor symmetry. Our
scenario induces lepton flavour violating (LFV) three body decays that can
proceed at the tree level, while radiative li to lj gamma decays and mu-e
conversion in nuclei are also expected to be sizeable. LFV decays are related
by the underlying flavor symmetry and the new fermions are also expected to be
accessible for study at the Large Hadron Collider (LHC)
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