123 research outputs found
Corrigendum to "An alternative method of determining the neutrino mass ordering in reactor neutrino experiments" [Phys. Lett. B 772 (2017) 179–183]
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Lepton Numbers in the framework of Neutrino Mixing
In this short review we discuss the notion of lepton numbers. The strong
evidence in favor of neutrino oscillations obtained recently in the
Super-Kamiokande atmospheric neutrino experiment and in solar neutrino
experiments imply that the law of conservation of family lepton numbers L_e,
L_mu and L_tau is strongly violated. We consider the states of flavor neutrinos
nu_e, nu_mu and nu_tau and we discuss the evolution of these states in space
and time in the case of non-conservation of family lepton numbers due to the
mixing of light neutrinos. We discuss and compare different flavor neutrino
discovery experiments. We stress that experiments on the search for
nu_mu->nu_tau and nu_e->nu_tau oscillations demonstrated that the flavor
neutrino nu_tau is a new type of neutrino, different from nu_e and nu_mu. In
the case of neutrino mixing, the lepton number (only one) is connected with the
nature of massive neutrinos. Such conserved lepton number exist if massive
neutrinos are Dirac particles. We review possibilities to check in future
experiments whether the conserved lepton number exists.Comment: 20 page
Present Status of Neutrino Mixing
A short review of the status of neutrino mixing and neutrino oscillations is
given. The basics of neutrino mixing and oscillations is discussed. The latest
evidences of neutrino oscillations obtained in the Super-Kamiokande and the SNO
solar neutrino experiments and in the Super-Kamiokande atmospheric neutrino
experiment are considered. The results of solar and atmospheric neutrino
experiments are discussed from the point of view of the three-neutrino mixing.Comment: 20 pages, Proceedings of the Advanced Study Institute "Symmetries and
Spin", Praha-Spin-2001, Czech Republic, July 15-28, 200
CP-violating Majorana phases, lepton-conserving processes and final state interactions
The CP-violating phases associated with Majorana neutrinos can give rise to
CP-violating effects even in processes that conserve total Lepton number, such
as \mu -> eee+, \mu + e -> e + e and others. After explaining the reasons that
make this happen, we consider the calculation of the rates for the process of
the form \ell_a + \ell_b -> \ell_a + \ell_c, and its conjugate \bar\ell_a +
\bar\ell_b -> \bar\ell_a + \bar\ell_c, where \ell_a, \ell_b and \ell_c denote
charged leptons of different flavors. In the context of the Standard Model with
Majorana neutrinos, we show that the difference in the rates depends on such
phases. Our calculations illustrate in detail the mechanics that operate behind
the scene, and set the stage for carrying out the analogous, more complicated
(as we explain), calculations for other processes such as \mu -> eee+ and its
conjugate.Comment: Latex, axodraw, 24 page
The Interplay Between the "Low" and "High" Energy CP-Violation in Leptogenesis
We analyse within the "flavoured" leptogenesis scenario of baryon asymmetry
generation, the interplay of the "low energy" CP-violation, originating from
the PMNS neutrino mixing matrix , and the "high energy" CP-violation which
can be present in the matrix of neutrino Yukawa couplings, , and can
manifest itself only in "high" energy scale processes. The type I see-saw model
with three heavy right-handed Majorana neutrinos having hierarchical spectrum
is considered. The "orthogonal" parametrisation of the matrix of neutrino
Yukawa couplings, which involves a complex orthogonal matrix , is employed.
In this approach the matrix is the source of "high energy" CP-violation.
Results for normal hierarchical (NH) and inverted hierarchical (IH) light
neutrino mass spectrum are derived in the case of decoupling of the heaviest RH
Majorana neutrino. It is shown that taking into account the contribution to
due to the CP-violating phases in the neutrino mixing matrix can
change drastically the predictions for , obtained assuming only "high
energy" CP-violation from the -matrix is operative in leptogenesis. In the
case of IH spectrum, in particular, there exist significant regions in the
corresponding parameter space where the purely "high energy" contribution in
plays a subdominant role in the production of baryon asymmetry compatible
with the observations.Comment: Results unchanged; comments and references added; version to be
puplished in Eur.Phys.J.
Charged Lepton Decays L_i to L_j + gamma, Leptogenesis CP-Violating Parameters and Majorana Phases
We analyse the dependence of the rates of the LFV charged lepton decays mu to
e + gamma, tau to e + gamma, tau to mu + gamma (l_i to l_j + gamma) and their
ratios, predicted in the class of SUSY theories with see-saw mechanism of
nu-mass generation and soft SUSY breaking with universal boundary conditions at
the GUT scale, on the Majorana CP-violation phases in the PMNS neutrino mixing
matrix and the ``leptogenesis'' CP-violating (CPV) parameters. The case of
quasi-degenerate in mass heavy Majorana neutrinos is considered. The analysis
is performed for normal hierarchical (NH), inverted hierarchical (IH) and
quasi-degenerate (QD) light neutrino mass spectra. We show, in particular, that
for NH and IH nu-mass spectrum and negligible lightest neutrino mass, all three
l_i to l_j + gamma decay branching ratios, BR(l_i to l_j + gamma), depend on
one Majorana phase, one leptogenesis CPV parameter and on the 3-neutrino
oscillation parameters; if the CHOOZ mixing angle theta_13 is sufficiently
large, they depend on the Dirac CPV phase in the PMNS matrix. The ``double
ratios'' R(21/31) sim BR(mu to e + gamma)/BR(tau to e + gamma) and R(21/32) sim
BR(mu to e + gamma)/BR(tau to mu + gamma) are determined by these parameters.
The same Majorana phase enters into the NH and IH expressions for the effective
Majorana mass in neutrinoless double beta decay, .Comment: 27 pages, 5 figures, version to be published in Physical Review
The mu - e Conversion in Nuclei, mu --> e gamma, mu --> 3e Decays and TeV Scale See-Saw Scenarios of Neutrino Mass Generation
We perform a detailed analysis of lepton flavour violation (LFV) within
minimal see-saw type extensions of the Standard Model (SM), which give a viable
mechanism of neutrino mass generation and provide new particle content at the
electroweak scale. We focus, mainly, on predictions and constraints set on each
scenario from mu --> e gamma, mu --> 3e and mu - e conversion in the nuclei. In
this class of models, the flavour structure of the Yukawa couplings between the
additional scalar and fermion representations and the SM leptons is highly
constrained by neutrino oscillation measurements. In particular, we show that
in some regions of the parameters space of type I and type II see-saw models,
the Dirac and Majorana phases of the neutrino mixing matrix, the ordering and
hierarchy of the active neutrino mass spectrum as well as the value of the
reactor mixing angle theta_{13} may considerably affect the size of the LFV
observables. The interplay of the latter clearly allows to discriminate among
the different low energy see-saw possibilities.Comment: Expressions for the factors |C_{me}|^2 and |C_{mu3e}|^2 in the mu-e
conversion and mu-->3e decay rates, eqs. (36) and (49), respectively,
corrected; results in subsections 2.2 and 2.3 quantitatively changed,
qualitatively remain the same; figures 2, 3, 4 and 5 replace
Analytical description of quasivacuum oscillations of solar neutrinos
We propose a simple prescription to calculate the solar neutrino survival
probability P_{ee} in the quasivacuum oscillation (QVO) regime. Such
prescription is obtained by matching perturbative and exact analytical results,
which effectively take into account the density distribution in the Sun as
provided by the standard solar model. The resulting analytical recipe for the
calculation of P_{ee} is shown to reach its highest accuracy |\Delta P_{ee}| <
2.6 x 10^{-2} in the whole QVO range) when the familiar prescription of
choosing the solar density scale parameter r_0 at the
Mikheyev-Smirnov-Wolfenstein (MSW) resonance point is replaced by a new one,
namely, when r_0 is chosen at the point of ``maximal violation of
adiabaticity'' (MVA) along the neutrino trajectory in the Sun. The MVA
prescription admits a smooth transition from the QVO regime to the MSW
transition one. We discuss in detail the phase acquired by neutrinos in the
Sun, and show that it might be of relevance for the studies of relatively short
timescale variations of the fluxes of the solar \nu lines in the future
real-time solar neutrino experiments. Finally, we elucidate the role of matter
effects in the convective zone of the Sun.Comment: 25 pages (RevTeX) + 11 figures (postscript
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