11 research outputs found
Radiative corrections to neutrino mass matrix in the Standard Model and beyond
We study the effect of radiative corrections on the structure of neutrino
mass matrix. We analyze the renormalization of the matrix from the electroweak
scale to the scale at which the effective operator that gives
masses to neutrinos is generated. Apart from Standard Model and MSSM,
non-standard extensions of SM are considered at a scale intermediate
between and . We find that the dominant structure of the neutrino
mass matrix does not change. SM and MSSM corrections produce small (few
percents) independent renormalization of each matrix element. Non-standard
(flavor changing) corrections can modify strongly small (sub-dominant) matrix
elements, which are important for the low energy phenomenology. In particular,
we show that all sub-dominant elements can have purely radiative origin, being
zero at . The set of non-zero elements at can be formed by (i)
diagonal elements (unit matrix); (ii) and ; (iii)
and -block elements; (iv) -block elements. In the case of
unit matrix, both atmospheric and solar mixing angles and mass squared
differences are generated radiatively.Comment: 22 pages, 5 eps figures, JHEP3.cls, some clarifications and one
reference adde
Maximum likelihood analysis of the first KamLAND results
A maximum likelihood approach has been used to analize the first results from
KamLAND emphasizing the application of this method for low statistics samples.
The goodness of fit has been determined exploiting a simple Monte Carlo
approach in order to test two different null hytpotheses. It turns out that
with the present statistics the neutrino oscillation hypothesis has a
significance of about 90% (the best-fit for the oscillation parameters from
KamLAND are found to be: eV and
), while the no-oscillation hypothesis of
about 50%. Through the likelihood ratio the hypothesis of no disappearence is
rejected at about 99.9% C.L. with the present data from the positron spectrum.
A comparison with other analyses is presented.Comment: 14 pages, 5 figure
Supernova Neutrino Spectrum with Matter and Spin Flavor Precession Effects
We consider Majorana neutrino conversions inside supernovae by taking into
account both flavor mixing and the neutrino magnetic moment. We study the
adiabaticity of various possible transitions between the neutrino states for
both normal and inverted hierarchy within the various solar neutrino problem
solutions. From the final mass spectrum within diffrent scenarios, we infer the
consequences of the various conversion effects on the neutronization peak, the
nature of final spectra, and the possible Earth matter effect on the final
fluxes. This enable us to check the sensibility of the SN neutrino flux on
magnetic moment interaction, and narrow down possible scenarios which depend
on: the mass spectrum normal or inverted, the solution of the solar neutrino
problem; and the value of MuxB.Comment: 24pages, 7 figure
Future Precision Neutrino Oscillation Experiments and Theoretical Implications
Future neutrino oscillation experiments will lead to precision measurements
of neutrino mass splittings and mixings. The flavour structure of the lepton
sector will therefore at some point become better known than that of the quark
sector. This article discusses the potential of future oscillation experiments
on the basis of detailed simulations with an emphasis on experiments which can
be done in about ten years. In addition, some theoretical implications for
neutrino mass models will be briefly discussed.Comment: Talk given at Nobel Symposium 2004: Neutrino Physics, Haga Slott,
Enkoping, Sweden, 19-24 Aug 200
MSLED, Neutrino Oscillations and the Cosmological Constant
We explore the implications for neutrino masses and mixings within the
minimal version of the supersymmetric large-extra-dimensions scenario (MSLED).
This model was proposed in {\tt hep-ph/0404135} to extract the phenomenological
implications of the promising recent attempt (in {\tt hep-th/0304256}) to
address the cosmological constant problem. Remarkably, we find that the
simplest couplings between brane and bulk fermions within this approach can
lead to a phenomenologically-viable pattern of neutrino masses and mixings that
is also consistent with the supernova bounds which are usually the bane of
extra-dimensional neutrino models. Under certain circumstances the MSLED
scenario can lead to a lepton mixing (PMNS) matrix close to the so-called
bi-maximal or the tri-bimaximal forms (which are known to provide a good
description of the neutrino oscillation data). We discuss the implications of
MSLED models for neutrino phenomenology.Comment: 38 pages, 1 figure; Reposted with a few additional reference
On the search for neutrino oscillations using an artificial neutrino source
In this paper the possibility of searching for neutrino oscillations with an artificial neutrino source is discussed and a comparison with reactor experiments is carried out
Models of Neutrino Masses and Mixings
We review theoretical ideas, problems and implications of neutrino masses and
mixing angles. We give a general discussion of schemes with three light
neutrinos. Several specific examples are analyzed in some detail, particularly
those that can be embedded into grand unified theories.Comment: 44 pages, 2 figures, version accepted for publication on the Focus
Issue on 'Neutrino Physics' edited by F.Halzen, M.Lindner and A. Suzuki, to
be published in New Journal of Physics
Search for neutrinos in coincidence with gravitational wave events from the LIGOâVirgo O3a observing run with the Super-Kamiokande detector
The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGOâVirgo Collaboration (LVC). Both low-energy (7â100 MeV) and high-energy (0.1â105 GeV) samples were analyzed in order to cover a very wide neutrino spectrum. Follow-ups of 36 (out of 39) gravitational waves reported in the GWTC-2 catalog were examined; no significant excess above the background was observed, with 10 (24) observed neutrinos compared with 4.8 (25.0) expected events in the high-energy (low-energy) samples. A statistical approach was used to compute the significance of potential coincidences. For each observation, p-values were estimated using neutrino direction and LVC sky map; the most significant event (GW190602_175927) is associated with a post-trial p-value of 7.8% (1.4Ï). Additionally, flux limits were computed independently for each sample and by combining the samples. The energy emitted as neutrinos by the identified gravitational wave sources was constrained, both for given flavors and for all flavors assuming equipartition between the different flavors, independently for each trigger and by combining sources of the same nature