4,957 research outputs found
Energy and Momentum of Oscillating Neutrinos
It is shown that Lorentz invariance implies that in general flavor neutrinos
in oscillation experiments are superpositions of massive neutrinos with
different energies and different momenta. It is also shown that for each
process in which neutrinos are produced there is either a Lorentz frame in
which all massive neutrinos have the same energy or a Lorentz frame in which
all massive neutrinos have the same momentum. In the case of neutrinos produced
in two-body decay processes, there is a Lorentz frame in which all massive
neutrinos have the same energy.Comment: 6 pages, no figure
Neutrinoless double-beta decay. A brief review
In this brief review we discuss the generation of Majorana neutrino masses
through the see-saw mechanism, the theory of neutrinoless double-beta decay,
the implications of neutrino oscillation data for the effective Majorana mass,
taking into account the recent Daya Bay measurement of theta_13, and the
interpretation of the results of neutrinoless double-beta decay experiments.Comment: 22 page
Hyperkähler cones and instantons on quaternionic Kähler manifolds
We present a novel approach to the study of Yang-Mills instantons on quaternionic Kähler manifolds, based on an extension of the harmonic space method of constructing instantons on hyperk\"ahler manifolds. Our results establish a bijection between local equivalence classes of instantons on quaternionic Kähler manifolds M and equivalence classes of certain holomorphic maps on an appropriate SL_2(C)-bundle over the Swann bundle of M
Intermediate Symmetries in the Spontaneous Breaking of Supersymmetric SO(10)
We study the supersymmetric spontaneous symmetry breaking of SO(10) into
SU(3)xSU(2)xU(1) for the most physically interesting cases of SU(5) or flipped
SU(5)xU(1) intermediate symmetries. The first case is more easily realized
while the second one requires a fine-tuning condition on the parameters of the
superpotential. This is because in the case of SU(5) symmetry there is at most
one singlet of the residual symmetry in each SO(10) irreducible representation.
We also point out on more general grounds in supersymmetric GUT's that some
intermediate symmetries can be exactly realized and others can only be
approximated by fine-tuning. In the first category, there could occur some
tunneling between the vacua with exact and approximate intermediate symmetry.
The flipped SU(5)xU(1) symmetry improves the unification of gauge couplings if
(B-L) is broken by (B-L)=1 scalars yielding right handed neutrino masses below
10^{14} GeV}.Comment: LaTex, 9 page
Relating Neutrino Masses by dilepton modes of Doubly Charged Scalars
We study a model with Majorana neutrino masses generated through doubly
charged scalars at two-loop level. We give explicit relationships between the
neutrino masses and the same sign dilepton decays of the doubly charged
scalars. In particular, we demonstrate that at the tribimaximal limit of the
neutrino mixings, the absolute neutrino masses and Majorana phases can be
extracted through the measurements of the dilepton modes at colliders.Comment: 14 pages, 8 figures, references added, version to be published in PR
Possible tests for sterile neutrinos
It is shown that the future SNO and Super-Kamiokande experiments, in which
high energy neutrinos will be detected through the observation
of CC, NC and -- elastic scattering processes, could allow to reveal in
a model independent way the presence of sterile neutrinos in the flux of solar
neutrinos on the earth.Comment: Latex file, 6 pages including 1 figure. The postscript file of text
and figures is available at http://www.to.infn.it/teorici/giunti/papers.html
or ftp://ftp.to.infn.it/pub/giunti/1995/dftt-84-95/dftt-84-95.p
Neutrino Physics
The basic concepts of neutrino physics are presented at a level appropriate
for integration into elementary courses on quantum mechanics and/or modern
physics.Comment: Prepared for the American Journal of Physics; 50 pages; 11 figures
(10 included); late
Patterns in the Fermion Mixing Matrix, a bottom-up approach
We first obtain the most general and compact parametrization of the unitary
transformation diagonalizing any 3 by 3 hermitian matrix H, as a function of
its elements and eigenvalues. We then study a special class of fermion mass
matrices, defined by the requirement that all of the diagonalizing unitary
matrices (in the up, down, charged lepton and neutrino sectors) contain at
least one mixing angle much smaller than the other two. Our new parametrization
allows us to quickly extract information on the patterns and predictions
emerging from this scheme. In particular we find that the phase difference
between two elements of the two mass matrices (of the sector in question)
controls the generic size of one of the observable fermion mixing angles: i.e.
just fixing that particular phase difference will "predict" the generic value
of one of the mixing angles, irrespective of the value of anything else.Comment: 29 pages, 3 figures, references added, to appear in PR
Left-right symmetric model with symmetry
We analyze the leptonic sector in the left-right symmetric model dressed with
a discrete symmetry which realizes, after weak spontaneous
breaking, a small broken \mu\lra\tau symmetry that is suggested to explain
observable neutrino oscillation data. \mu\lra\tau symmetry is broken at tree
level in the effective neutrino mass matrix due to the mass difference
in the diagonal Dirac mass
terms, whereas all lepton mixings arise from a Majorana mass matrix. In the
limit of a small breaking we determined , and the deviation from
the maximal value of , in terms of the light neutrino hierarchy
scale, , and a single free parameter of the model.Comment: 9 pages, 4 figures. Title changed and we have added one new section:
CP phase contribution. Minor corrections and references updated. Published
versio
Parametric resonance for antineutrino conversions using LSND best-fit results with a 3+1 flavor scheme
An analytical solution to a parametric resonance effect for antineutrinos in
a 3+1 flavor (active+sterile) scheme using multiple non-adiabatic density
shifts is presented. We derive the conditions for a full flavor conversion for
antineutrino oscillations
under the assumption that LSND best-fits for the mixing
parameters are valid in a short-baseline accelerator experiment. We show that
the parametric resonance effect can be exploited to increase the effective
antineutrino oscillation length by a factor of 10-40, thus sustaining a high
oscillation probability for a much longer period of time than in the vacuum
scenario. We propose a realistic experimental setup that could probe for this
effect which leaves a signature in terms of a specific oscillation probability
profile. Moreover, since the parametric resonance effect is valid in any 2 or
1+1 flavor approximation, our results could be suggestive for future
short-baseline accelerator neutrino detection experiments.Comment: 6 pages, 4 figure
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