194 research outputs found
A Three-Flavor, Lorentz-Violating Solution to the LSND Anomaly
We investigate whether postulating the existence of Lorentz-violating,
CPT-conserving interactions allows three-neutrino solutions to the LSND anomaly
that are also consistent with all other neutrino data. We show that
Lorentz-violating interactions that couple only to one of the active neutrinos
have the right properties to explain all the data. The details of the data make
this solution unattractive. We find, for example, that a highly non-trivial
energy dependence of the Lorentz-violating interactions is required.Comment: 15 pages, two eps figures. V2 - Minor modification
Theoretical Aspects of Neutrino Oscillation
I review some aspects concerning the physics of neutrino mixing and
oscillations. I discuss in some detail the physical neutrino oscillations
parameter space in the case of two and three family mixing, and briefly
describe the current knowledge of neutrino mixing parameters according to the
present solar, atmospheric, and reactor neutrino data. I also briefly comment
on the possibility of solving the LNSD anomaly together with the solar and
atmospheric ones. I conclude by emphasising that that even though in five to
ten years time a lot will be learnt from the next round of neutrino
experiments, a great deal about neutrino masses and neutrino mixing will remain
unknown.Comment: Invited Plenary Talk at the NUFACT'01 Conference, 14 pages, 2 figure
Addressing the Majorana vs. Dirac Question with Neutrino Decays
The Majorana versus Dirac nature of neutrinos remains an open question. This
is due, in part, to the fact that virtually all the experimentally accessible
neutrinos are ultra-relativistic. Noting that Majorana neutrinos can behave
quite differently from Dirac ones when they are non-relativistic, we show that,
at leading order, the angular distribution of the daughters in the decay of a
heavy neutrino into a lighter one and a self-conjugate boson is isotropic in
the parent's rest frame if the neutrinos are Majorana, independent of the
parent's polarization. If the neutrinos are Dirac fermions, this is, in
general, not the case. This result follows from CPT invariance and is
independent of the details of the physics responsible for the decay. We explore
the feasibility of using these angular distributions -- or, equivalently, the
energy distributions of the daughters in the laboratory frame -- in order to
address the Majorana versus Dirac nature of neutrinos if a fourth, heavier
neutrino mass eigenstate reveals itself in the current or next-generation of
high-energy colliders, intense meson facilities, or neutrino beam experiments.Comment: 11 pages, 3 figure
The Dark Side of the Solar Neutrino Parameter Space
Results of neutrino oscillation experiments have always been presented on the
(sin^2 2theta, Delta m^2) parameter space for the case of two-flavor
oscillations. We point out, however, that this parameterization misses the half
of the parameter space pi/4 < theta <= pi/2 (``the dark side''), which is
physically inequivalent to the region 0 <= theta <= pi/4 (``the light side'')
in the presence of matter effects. The MSW solutions to the solar neutrino
problem can extend to the dark side, especially if we take the conservative
attitude to allow higher confidence levels, ignore some of the experimental
results in the fits, or relax theoretical predictions. Furthermore even the
so-called ``vacuum oscillation'' solution distinguishes the dark and the light
sides. We urge experimental collaborations to present their results on the
entire parameter space.Comment: 4 pages, 3 figures, uses psfig. Fixed typos in Eq. (3). An imprecise
comment in the footnote remove
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