3,949 research outputs found
Which long-baseline neutrino experiments are preferable?
We discuss the physics of superbeam upgrades, where we focus on T2KK, a NuMI
beam line based experiment NOvA*, and a wide band beam (WBB) experiment
independent of the NuMI beam line. For T2KK, we find that the Japan-Korea
baseline helps resolve parameter degeneracies, but the improvement due to
correlated systematics between the two detectors (using identical detectors) is
only moderate. For an upgrade of NOvA with a liquid argon detector, we
demonstrate that the Ash River site is preferred compared to alternatives, such
as at the second oscillation maximum, and is the optimal site within the U.S.
For a WBB experiment, we find that high proton energies and long decay tunnels
are preferable. We compare water Cherenkov and liquid argon technologies, and
find the break-even point in detector cost at about 4:1. In order to compare
the physics potential of the different experimental configurations, we use the
concept of exposure to normalize the performance. We find that experiments with
WBBs are the best experimental concept. NOvA* could be competitive with
sufficient luminosity. If > 0.01, a WBB experiment can
perform better than a neutrino factory.Comment: 31 pages, 13 figures, 5 tables. Version to appear in PR
Neutrino Decay and Atmospheric Neutrinos
We reconsider neutrino decay as an explanation for atmospheric neutrino
observations. We show that if the mass-difference relevant to the two mixed
states \nu_\mu and \nu_\tau is very small (< 10^{-4} eV^2), then a very good
fit to the observations can be obtained with decay of a component of \nu_\mu to
a sterile neutrino and a Majoron. We discuss how the K2K and MINOS
long-baseline experiments can distinguish the decay and oscillation scenarios.Comment: 9 pages, Revtex, uses epsf.sty, 3 postscript figures. Additions and
corrections to references, minor changes in the text and to some number
Inverting a Supernova: Neutrino Mixing, Temperatures and Binding Energy
We show that the temperatures of the emergent non-electron neutrinos and the
binding energy released by a galactic Type II supernova are determinable,
assuming the Large Mixing Angle (LMA) solution is correct, from observations at
the Sudbury Neutrino Observatory (SNO) and at Super-Kamiokande (SK). If the
neutrino mass hierarchy is inverted, either a lower or upper bound can be
placed on the neutrino mixing angle , and the hierarchy can be
deduced for adiabatic transitions. For the normal hierarchy, neither can
be constrained nor can the hierarchy be determined. Our
conclusions are qualitatively unchanged for the proposed Hyper-Kamiokande
detector.Comment: Following astro-ph/0208035, we adopt electron and non-electron
neutrino spectra with very small differences. Conclusions change
General Issues in the Evolution of Fermion Masses and Mixings
General issues in the renormalization group evolution of fermion masses and
mixings is discussed. An effective fixed point in the top quark Yukawa coupling
can strongly constrain its value at the electroweak scale. Predictions
following from Yukawa coupling unification are affected by threshold
corrections at the grand unified scale. The Landau pole translates into an
upper limit on the strong gauge coupling . Given the hierarchy
in the fermion sector, the evolution of the Cabbibo-Kobayashi-Maskawa matrix
can be expressed in terms of a single scaling parameter . Using this scaling
factor and analogous scaling factors for the quark and lepton masses, we
outline a systematic strategy that readily yields electroweak predictions for
any GUT scale texture.}Comment: (Talk given at the SUSY93 Conference MSB), 9 pages + 3 PS figures not
included (available on request), MAD/PH/75
Testing neutrino instability with active galactic nuclei
Active galactic nuclei and gamma ray bursts at cosmological distances are
sources of high-energy electron and muon neutrinos and provide a unique test
bench for neutrino instability. The typical lifetime-to-mass ratio one can
reach there is s/eV. We study the rapid
decay channel , where is a massless or very light
scalar (possibly a Goldstone boson), and point out that one can test the
coupling strength of down to g_{ij}\lsim 10^{-8} eV/m by
measuring the relative fluxes of , and . This
is orders of magnitude more stringent bound than what one can obtain in other
phenomena, e.g. in neutrinoless double beta decay with scalar emission.Comment: 3 page
Neutrino Factories: Physics Potential
The physics potential of low-performance and high-performance neutrino
factories is briefly reviewed..Comment: Talk presented at NUFACT02, London, 1-6 July, 2002. 8 pages, 5
figure
Breaking Eight-fold Degeneracies in Neutrino CP Violation, Mixing, and Mass Hierarchy
We identify three independent two-fold parameter degeneracies (\delta,
\theta_{13}), sgn(\delta m^2_{31}) and (\theta_{23}, \pi/2-\theta_{23})
inherent in the usual three-neutrino analysis of long-baseline neutrino
experiments, which can lead to as much as an eight-fold degeneracy in the
determination of the oscillation parameters. We discuss the implications these
degeneracies have for detecting CP violation and present criteria for breaking
them. A superbeam facility with a baseline at least as long as the distance
between Fermilab and Homestake (1290 km) and a narrow band beam with energy
tuned so that the measurements are performed at the first oscillation peak can
resolve all the ambiguities other than the (\theta_{23}, \pi/2-\theta_{23})
ambiguity (which can be resolved at a neutrino factory) and a residual (\delta,
\pi-\delta) ambiguity. However, whether or not CP violation occurs in the
neutrino sector can be ascertained independently of the latter two ambiguities.
The (\delta,\pi-\delta) ambiguity can be eliminated by performing a second
measurement to which only the \cos\delta terms contribute. The hierarchy of
mass eigenstates can be determined at other oscillation peaks only in the most
optimistic conditions, making it necessary to use the first oscillation
maximum. We show that the degeneracies may severely compromise the ability of
the proposed SuperJHF-HyperKamiokande experiment to establish CP violation. In
our calculations we use approximate analytic expressions for oscillation
probabilitites that agree with numerical solutions with a realistic Earth
density profile.Comment: Revtex (singlespaced), 35 pages, 15 postscript figures, uses
psfig.st
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