884 research outputs found
Random magnetic fields inducing solar neutrino spin-flavor precession in a three generation context
We study the effect of random magnetic fields in the spin-flavor precession
of solar neutrinos in a three generation context, when a non-vanishing
transition magnetic moment is assumed. While this kind of precession is
strongly constrained when the magnetic moment involves the first family, such
constraints do not apply if we suppose a transition magnetic moment between the
second and third families. In this scenario we can have a large non-electron
anti-neutrino flux arriving on Earth, which can lead to some interesting
phenomenological consequences, as, for instance, the suppression of day-night
asymmetry. We have analyzed the high energy solar neutrino data and the KamLAND
experiment to constrain the solar mixing angle, and solar mass difference, and
we have found a larger shift of allowed values.Comment: 10 pages, 3 figure
Bilarge neutrino mixing from supersymmetry with high-scale nonrenormalizable interactions
We suggest a supersymmetric (SUSY) explanation of neutrino masses and mixing,
where nonrenormalizable interactions in the hidden sector generate lepton
number violating Majorana mass terms for both right-chiral sneutrinos and
neutrinos. It is found necessary to start with a superpotential including an
array of gauge singlet chiral superfields. This leads to nondiagonal mass terms and almost diagonal SUSY breaking -terms. As a result, the
observed pattern of bilarge mixing can be naturally explained by the
simultaneous existence of the seesaw mechanism and radiatively induced masses.
Allowed ranges of parameters in the gauge singlet sector are delineated,
corresponding to each of the cases of normal hierarchy, inverted hierarchy and
degenerate neutrinos.Comment: 19 pages, 5 figures. Minor modifications are made in the title and
the text, some new references are added. To appear in this form in Physical
Review
Masses and Mixings from Neutrino Beams pointing to Neutrino Telescopes
We discuss the potential to determine leading oscillation parameters, the
value and the sign of \Delta m^2_{31}, as well as the magnitude of \sin^2
2\theta_{13} using a conventional wide band neutrino beam pointing to water or
ice Cherenkov neutrino detectors known as ``Neutrino Telescopes''. We find that
precision measurements of \Delta m^2_{31} and \theta_{23} are possible and
that, even though it is not possible to discriminate between charges in the
detector, there is a remarkably good sensitivity to the mixing angle
\theta_{13} and the sign of \Delta m^2_{31}.Comment: 9 pages, 4 figure
Flavor Evolution of the Neutronization Neutrino Burst from an O-Ne-Mg Core-Collapse Supernova
We present results of 3-neutrino flavor evolution simulations for the
neutronization burst from an O-Ne-Mg core-collapse supernova. We find that
nonlinear neutrino self-coupling engineers a single spectral feature of
stepwise conversion in the inverted neutrino mass hierarchy case and in the
normal mass hierarchy case, a superposition of two such features corresponding
to the vacuum neutrino mass-squared differences associated with solar and
atmospheric neutrino oscillations. These neutrino spectral features offer a
unique potential probe of the conditions in the supernova environment and may
allow us to distinguish between O-Ne-Mg and Fe core-collapse supernovae.Comment: 4 pages, 2 figures. Version accepted by PR
Neutrino Mass Hierarchy and Stepwise Spectral Swapping of Supernova Neutrino Flavors
We examine a phenomenon recently predicted by numerical simulations of
supernova neutrino flavor evolution: the swapping of supernova and
energy spectra below (above) energy \EC for the normal
(inverted) neutrino mass hierarchy. We present the results of large-scale
numerical calculations which show that in the normal neutrino mass hierarchy
case, \EC decreases as the assumed
effective vacuum mixing angle () is decreased.
However, these calculations also indicate that \EC is essentially independent
of the vacuum mixing angle in the inverted neutrino mass hierarchy case. With a
good neutrino signal from a future Galactic supernova, the above results could
be used to determine the neutrino mass hierarchy even if is too
small to be detected in terrestrial neutrino oscillation experiments.Comment: 4 pages, 2 figures. Version accepted by PR
Construction and analysis of a simplified many-body neutrino model
In dense neutrino systems, such as found in the early Universe, or near a
supernova core, neutrino flavor evolution is affected by coherent
neutrino-neutrino scattering. It has been recently suggested that many-particle
quantum entanglement effects may play an essential role in these systems,
potentially invalidating the traditional description in terms of a set of
single-particle evolution equations. We model the neutrino system by a system
of interacting spins, following an earlier work which showed that such a spin
system can in some cases be solved exactly. We extend this work by constructing
an exact analytical solution to a more general spin system, including initial
states with asymmetric spin distribution and, moreover, not necessarily aligned
along the same axis. Our solution exhibits a rich set of behaviors, including
coherent oscillations and dephasing and a transition from the classical to
quantum regimes. We argue that the classical evolution of the spin system
captures the entire coherent behavior of the neutrino system, while the quantum
effects in the spin system capture some, but not all, of the neutrino
incoherent evolution. By comparing the spin and neutrino systems, we find no
evidence for the violation of the accepted one-body description, though the
argument involves some subtleties not appreciated before. The analysis in this
paper may apply to other two-state systems beyond the neutrino field.Comment: 22 pages, 7 figure
Approximative two-flavor framework for neutrino oscillations with nonstandard interactions
In this paper, we develop approximative two-flavor neutrino oscillation
formulas including subleading nonstandard interaction effects. Especially, the
limit when the small mass-squared difference approaches zero is investigated.
The approximate formulas are also tested against numerical simulations in order
to determine their accuracy and they will probably be most useful in the GeV
energy region, which is the energy region where most upcoming neutrino
oscillation experiments will be operating. Naturally, it is important to have
analytical formulas in order to interpret the physics behind the degeneracies
between standard and nonstandard parameters.Comment: 21 pages, 7 figures, REVTeX4. Final version published in Phys. Rev.
Earth Matter Effects in Detection of Supernova Neutrinos
We calculated the matter effect, including both the Earth and supernova, on
the detection of neutrinos from type II supernovae at the proposed Daya Bay
reactor neutrino experiment. It is found that apart from the dependence on the
flip probability P_H inside the supernova and the mass hierarchy of neutrinos,
the amount of the Earth matter effect depends on the direction of the incoming
supernova neutrinos, and reaches the biggest value when the incident angle of
neutrinos is around 93^\circ. In the reaction channel \bar{\nu}_e + p --> e^+ +
n the Earth matter effect can be as big as about 12%. For other detection
processes the amount of the Earth matter effect is a few per cent.Comment: 13 pages, 5 figure
Neutrino Oscillations in the Early Universe: A Real Time Formulation
Neutrino oscillations in the early Universe prior to the epoch of primordial
nucleosynthesis is studied by implementing real time non-equilibrium field
theory methods. We focus on two flavors of Dirac neutrinos, however, the
formulation is general. We obtain the equations of motion for neutrino
wavepackets of either chirality and helicity in the plasma allowing for CP
asymmetry. Contributions non-local in space-time to the self-energy dominate
over the asymmetry for if the lepton and neutrino
asymmetries are of the same order as the baryon asymmetry. We find a new
contribution which cannot be interpreted as the usual effective potential. The
mixing angles and dispersion relations in the medium depend on \emph{helicity}.
We find that resonant transitions are possible in the temperature range . Near a resonance in the mixing angle, the
oscillation time scale in the medium as compared to the vacuum is
\emph{slowed-down} substantially for small vacuum mixing angle. The time scale
of oscillations \emph{speeds-up} for off resonance high energy neutrinos for
which the mixing angle becomes vanishingly small. The equations of motion
reduce to the familiar oscillation formulae for negative helicity
ultrarelativistic neutrinos, but include consistently both the \emph{mixing
angle and the oscillation frequencies in the medium}. These equations of motion
also allow to study the dynamics of right handed as well as positive helicity
neutrinos.Comment: 31 pages 2 figures. Version to appear in Phys. Rev.
Density Fluctuation Effects on Collective Neutrino Oscillations in O-Ne-Mg Core-Collapse Supernovae
We investigate the effect of matter density fluctuations on supernova
collective neutrino flavor oscillations. In particular, we use full
multi-angle, 3-flavor, self-consistent simulations of the evolution of the
neutrino flavor field in the envelope of an O-Ne-Mg core collapse supernova at
shock break-out (neutrino neutronization burst) to study the effect of the
matter density "bump" left by the He-burning shell. We find a seemingly
counterintuitive increase in the overall electron neutrino survival probability
created by this matter density feature. We discuss this behavior in terms of
the interplay between the matter density profile and neutrino collective
effects. While our results give new insights into this interplay, they also
suggest an immediate consequence for supernova neutrino burst detection: it
will be difficult to use a burst signal to extract information on fossil
burning shells or other fluctuations of this scale in the matter density
profile. Consistent with previous studies, our results also show that the
interplay of neutrino self-coupling and matter fluctuation could cause a
significant increase in the electron neutrino survival probability at very low
energyComment: 12 pages, 11 figures. This is a pre-submission version of the pape
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