663 research outputs found
Exploring Neutrino Oscillations with Superbeams
We consider the medium- and long-baseline oscillation physics capabilities of
intense muon-neutrino and muon-antineutrino beams produced using future
upgraded megawatt-scale high-energy proton beams. In particular we consider the
potential of these conventional neutrino ``superbeams'' for observing
\nu_\mu\to\nu_e oscillations, determining the hierarchy of neutrino mass
eigenstates, and measuring CP-violation in the lepton sector. The physics
capabilities of superbeams are explored as a function of the beam energy,
baseline, and the detector parameters. The trade-offs between very large
detectors with poor background rejection and smaller detectors with excellent
background rejection are illustrated. We find that it may be possible to
observe \nu_\mu\to\nu_e oscillations with a superbeam provided that the
amplitude parameter \sin^2 2\theta_{13} is larger than a few \times 10^{-3}. If
\sin^2 2\theta_{13} is of order 10^{-2} or larger, then the neutrino mass
hierarchy can be determined in long-baseline experiments, and if in addition
the large mixing angle MSW solution describes the solar neutrino deficit then
there is a small region of parameter space within which maximal CP-violation in
the lepton sector would be observable in a low-energy medium-baseline
experiment. We explicitly consider massive water Cherenkov and liquid argon
detectors at superbeams with neutrino energies ranging from 1 GeV to 15 GeV,
and baselines from 295 km to 9300 km. Finally, we compare the oscillation
physics prospects at superbeams with the corresponding prospects at neutrino
factories. The sensitivity at a neutrino factory to CP violation and the
neutrino mass hierarchy extends to values of the amplitude parameter \sin^2
2\theta_{13} that are one to two orders of magnitude lower than at a superbeam.Comment: Revtex (singlespaced), 41 pages, uses epsf.sty, 12 postscript
figures. Minor corrections and notation changes, expanded discussions, x-axis
numbers added to Fig.9(a),(c). To be published in Phys. Rev.
Unknowns after the SNO Charged-Current Measurement
We perform a model-independent analysis of solar neutrino flux rates
including the recent charged-current measurement at the Sudbury Neutrino
Observatory (SNO). We derive a universal sum rule involving SNO and
SuperKamiokande rates, and show that the SNO neutral-current measurement can
not fix the fraction of solar oscillating to sterile neutrinos. The
large uncertainty in the SSM B flux impedes a determination of the sterile
neutrino fraction.Comment: Version to appear in PRL; includes analysis with anticipated SNO NC
measuremen
Unitarity And Anomalous Top-Quark Yukawa Couplings
Unitarity constraints on anomalous top-Higgs couplings are examined. We also
compare the unitarity constraints with the constraints from electroweak
baryogenesis and electric dipole moments derived earlier.Comment: Iowa State University Preprint, AMES-HET 94-11, (Tex file) 10 pages,
one Figure available by reques
Maximal atmospheric neutrino mixing and the small ratio of muon to tau mass
We discuss the problem of the small ratio of muon mass to tau mass in a class
of seesaw models where maximal atmospheric neutrino mixing is enforced through
a -- interchange symmetry. We introduce into those models an
additional symmetry such that in the case of exact
invariance. The symmetry may be softly broken in the Higgs potential, and
one thus achieves in a technically natural way. We speculate
on a wider applicability of this mechanism.Comment: 10 pages, plain LaTeX, no figures, minor changes, final version for
J. Phys.
Single Top Quark Production via FCNC Couplings at Hadron Colliders
We calculate single top-quark production at hadron colliders via the
chromo-magnetic flavor-changing neutral current couplings and . We find that the strength for the anomalous ()
coupling may be probed to () at the Tevatron with of data and
() at the LHC with of data. The two couplings may be
distinguished by a comparision of the single top signal with the direct top and
top decay signals for these couplings.Comment: 18 pages, 6 figures, 3 table
Limits on Non-Standard Top Quark Couplings from Electroweak Measurements
We calculate the typical size of loop corrections to electroweak observables
arising from non-standard and vertices. We use an
effective Lagrangian formalism based on the electroweak gauge group
. Limits on the non-standard model
top quark couplings from electroweak observables are presented and compared
with previously obtained limits.Comment: 9 pages, uses epsf.st
Phenomenology of a non-standard top quark Yukawa coupling
There are theoretical speculations that the top quark may have different
properties from that predicted by the standard model. We use an effective
Lagrangian technique to model such a non-standard top quark scenario and study
its effects on the electroweak baryogenesis, low and high energy physics.Comment: (TeX file, Figures available by request) AMES-HET 94-05, June 199
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