22 research outputs found
Comment on 'Time-energy uncertainty relations for neutrino oscillations and the Mossbauer neutrino experiment'
We discuss the implications of the time-energy uncertainty relation to
recoillessly emitted and captured neutrinos (Mossbauer neutrinos) and show that
it does not preclude oscillations of these neutrinos, contrary to a recent
claim (J. Phys. G35 (2008) 095003, arXiv:0803.0527).Comment: LaTeX, 6 pages, no figures; v2 has been extended compared to v1 and
matches the published version; title changed in journa
A Yukawa coupling parameterization for type I+ II seesaw formula and applications to lepton flavor violation and leptogenesis
In the type I + II seesaw formula the mass matrix of light neutrinos m_nu
receives contributions from the exchanges of both heavy Majorana neutrinos and
SU(2)_L-triplet Higgs bosons. We propose a new parameterization for the
Dirac-type Yukawa coupling matrix of neutrinos in this case, which generalizes
the well known Casas-Ibarra parameterization to type I + II seesaw and is
useful when the triplet term in m_nu is known. Neutrino masses and mixing,
lepton flavor violation in decays like mu -> e \gamma within mSUGRA models and
leptogenesis can then be studied within this framework. We illustrate the
usefulness of our new parameterization using a number of simple examples.Comment: 22 pages, 5 figure
Neutrino oscillograms of the Earth: effects of 1-2 mixing and CP-violation
We develop a comprehensive description of three flavor neutrino oscillations
inside the Earth in terms of neutrino oscillograms in the whole range of nadir
angles and for energies above 0.1 GeV. The effects of the 1-2 mass splitting
and mixing as well the interference of the 1-2 and 1-3 modes of oscillations
are quantified. The 1-2 mass splitting and mixing lead to the appearance, apart
from the resonance MSW peaks, of the parametric resonance peak for
core-crossing trajectories at E_nu ~= 0.2 GeV. We show that the interference
effects, in particular CP violation, have a domain structure with borders
determined by the solar and atmospheric magic lines and the lines of the
interference phase condition. The dependence of the oscillograms on the Dirac
CP-violating phase is studied. We show that for sin^2(2 theta13) < 0.1 the
strongest dependence of the oscillograms on delta is in the 1-2 and 1-3
resonance regions.Comment: 49 pages, LaTeX file using JHEP style, 13 figures included. Final
version to appear in JHE
A simple analytic three-flavour description of the day night effect in the solar neutrino flux
In the 3-flavour framework we derive a simple approximate analytic expression for the day-night difference of the flux of solar νe at terrestrial detectors which is valid for an arbitrary Earth density profile. Our formula has the accuracy of a few per cent and reproduces all the known analytic expressions for the Earth matter effects on the solar neutrino oscillations obtained under simplifying assumptions about the Earth's density profile (matter of constant density, 3 layers of constant densities, and adiabatic approximation). It can also be used for studying the Earth matter effects on the oscillations of supernova neutrinos. We also discuss the possibility of probing the leptonic mixing angle θ13 through day--night asymmetry measurements at future water Cherenkov solar neutrino detectors. We show that, depending on the measured value of the asymmetry, the current upper bound on θ13 may be improved, or even a lower bound on this mixing parameter may be obtained
Quantum field theoretic approach to neutrino oscillations in matter
We consider neutrino oscillations in non-uniform matter in a quantum field
theoretic (QFT) approach, in which neutrino production, propagation and
detection are considered as a single process. We find the conditions under
which the oscillation probability can be sensibly defined and demonstrate how
the properly normalized oscillation probability can be obtained in the QFT
framework. We derive the evolution equation for the oscillation amplitude and
discuss the conditions under which it reduces to the standard
Schr\"odinger-like evolution equation. It is shown that, contrary to the common
usage, the Schr\"odinger-like evolution equation is not applicable in certain
cases, such as oscillations of neutrinos produced in decays of free pions
provided that sterile neutrinos with eV exist.Comment: LaTeX, 24 pages + 16 pages of appendices, 1 figure. V2: typos
correcte
Neutrino oscillations: Quantum mechanics vs. quantum field theory
A consistent description of neutrino oscillations requires either the
quantum-mechanical (QM) wave packet approach or a quantum field theoretic (QFT)
treatment. We compare these two approaches to neutrino oscillations and discuss
the correspondence between them. In particular, we derive expressions for the
QM neutrino wave packets from QFT and relate the free parameters of the QM
framework, in particular the effective momentum uncertainty of the neutrino
state, to the more fundamental parameters of the QFT approach. We include in
our discussion the possibilities that some of the neutrino's interaction
partners are not detected, that the neutrino is produced in the decay of an
unstable parent particle, and that the overlap of the wave packets of the
particles involved in the neutrino production (or detection) process is not
maximal. Finally, we demonstrate how the properly normalized oscillation
probabilities can be obtained in the QFT framework without an ad hoc
normalization procedure employed in the QM approach.Comment: LaTeX, 42 pages, 1 figure; v2: minor clarifications, matches
published version; v3: Corrected the discussion of the conditions under which
an oscillation probability can be sensibly defined in the QFT approach (sec.
5.2.4
Supernova prompt neutronization neutrinos and neutrino magnetic moments
It is shown that the combined action of spin-flavor conversions of supernova
neutrinos due to the interactions of their Majorana-type transition magnetic
moments with the supernova magnetic fields and flavor conversions due to the
mass mixing can lead to the transformation of \nu_e born in the neutronization
process into their antiparticles \bar{\nu}_e. Such an effect would have a clear
experimental signature and its observation would be a smoking gun evidence for
the neutrino transition magnetic moments. It would also signify the leptonic
mixing parameter |U_{e3}| in excess of 10^{-2}.Comment: LaTex, 25 pages, 3 figures. v4: Discussion section expanded,
references added. Matches the published versio
Geotomography with solar and supernova neutrinos
We show how by studying the Earth matter effect on oscillations of solar and
supernova neutrinos inside the Earth one can in principle reconstruct the
electron number density profile of the Earth. A direct inversion of the
oscillation problem is possible due to the existence of a very simple analytic
formula for the Earth matter effect on oscillations of solar and supernova
neutrinos. From the point of view of the Earth tomography, these oscillations
have a number of advantages over the oscillations of the accelerator or
atmospheric neutrinos, which stem from the fact that solar and supernova
neutrinos are coming to the Earth as mass eigenstates rather than flavour
eigenstates. In particular, this allows reconstruction of density profiles even
over relatively short neutrino path lengths in the Earth, and also of
asymmetric profiles. We study the requirements that future experiments must
meet to achieve a given accuracy of the tomography of the Earth.Comment: 35 pages, 7 figures; minor textual changes in section
Supernova neutrinos: difference of nu_mu - nu_tau fluxes and conversion effects
The formalism of flavor conversion of supernova neutrinos is generalized to
include possible differences in the fluxes of the muon and tau neutrinos
produced in the star. In this case the radiatively induced difference of the
nu_mu and nu_tau potentials in matter becomes important. The nu_mu and nu_tau
flux differences can manifest themselves in the effects of the Earth matter on
the observed nu_e (antinu_e) signal if: (i) the neutrino mass hierarchy is
normal (inverted); (ii) the solution of the solar neutrino problem is in the
LMA region; (iii) the mixing U_{e3} is relatively large: |U_{e3}|>10^{-3}. We
find that for differences in the nu_mu - nu_tau (antinu_mu - antinu_tau)
average energies and/or integrated luminosities < 20 %, the relative deviation
of the observed nu_e (antinu_e) energy spectrum at E > 50 MeV from that in the
case of the equal fluxes can reach 20 - 30 % (10 - 15 %) for neutrinos crossing
the Earth. It could be detected in future if large detectors sensitive to the
nu_e (antinu_e) energy spectrum become available. The study of this effect
would allow one to test the predictions of the nu_mu, nu_tau, antinu_mu,
antinu_tau fluxes from supernova models and therefore give an important insight
into the properties of matter at extreme conditions. It should be taken into
account in the reconstruction of the neutrino mass spectrum and mixing matrix
from the supernova neutrino observations. We show that even for unequal nu_mu
and nu_tau fluxes, effects of leptonic CP violation can not be studied in the
supernova neutrino experiments.Comment: LaTeX, 34 pages, 10 figures; minor changes to text and figures,
references and acknowledgements adde
Probing the seesaw mechanism with neutrino data and leptogenesis
In the framework of the seesaw mechanism with three heavy right-handed
Majorana neutrinos and no Higgs triplets we carry out a systematic study of the
structure of the right-handed neutrino sector. Using the current low-energy
neutrino data as an input and assuming hierarchical Dirac-type neutrino masses
, we calculate the masses and the mixing of the heavy neutrinos.
We confront the inferred properties of these neutrinos with the constraints
coming from the requirement of a successful baryogenesis via leptogenesis. In
the generic case the masses of the right-handed neutrinos are highly
hierarchical: ; the lightest mass is GeV and the generated baryon-to-photon ratio is
much smaller than the observed value. We find the special cases which
correspond to the level crossing points, with maximal mixing between two
quasi-degenerate right-handed neutrinos. Two level crossing conditions are
obtained: (1-2 crossing) and (2-3
crossing), where and are respectively the 11-entry and the
12-subdeterminant of the light neutrino mass matrix in the basis where the
neutrino Yukawa couplings are diagonal. We show that sufficient lepton
asymmetry can be produced only in the 1-2 crossing where GeV, GeV and .Comment: 30 pages, 2 eps figures, JHEP3.cls, typos corrected, note (and
references) added on non-thermal leptogenesi