3,320 research outputs found
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
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
Determining the squark mass at the LHC
We propose a new way to determine the squark mass based on the shape of
di-jet invariant mass distribution of supersymmetry (SUSY) di-jet events at the
Large Hadron Collider (LHC). Our algorithm, which is based on event kinematics,
requires that the branching ratio is
substantial for at least some types of squarks, and that
. We select di-jet events with no
isolated leptons, and impose cuts on the total jet transverse energy,
, on , and on the
azimuthal angle between the two jets to reduce SM backgrounds. The shape of the
resulting di-jet mass distribution depends sensitively on the squark mass,
especially if the integrated luminosity is sufficient to allow a hard enough
cut on and yet leave a large enough signal to obtain the
distribution. We simulate the signal and Standard Model (SM) backgrounds for
100 fb integrated luminosity at 14 TeV requiring GeV.
We show that it should be possible to extract to within about
3% at 95% CL --- similar to the precision obtained using --- from the
di-jet mass distribution if GeV, or to within % if TeV.Comment: 20 pages, 9 figures. Footnote added, updated reference
Matter profile effect in neutrino factory
We point out that the matter profile effect --- the effect of matter density
fluctuation on the baseline --- is very important to estimate the parameters in
a neutrino factory with a very long baseline. To make it clear, we propose the
method of the Fourier series expansion of the matter profile. By using this
method, we can take account of both the matter profile effect and its
ambiguity. For very long baseline experiment, such as L=7332km, in the analysis
of the oscillation phenomena we need to introduce a new parameter ---
the Fourier coefficient of the matter profile --- as a theoretical parameter to
deal with the matter profile effects.Comment: 21 pages, 15 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
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
Systematic Exploration of the Neutrino Factory Parameter Space including Errors and Correlations
We discuss in a systematic way the extraction of neutrino masses, mixing
angles and leptonic CP violation at neutrino factories. Compared to previous
studies we put a special emphasis on improved statistical methods and on the
multidimensional nature of the combined fits of the nu_e -> nu_mu, \bar nu_e ->
\bar nu_mu appearance and nu_mu -> nu_mu, \bar nu_mu -> \bar nu_mu
disappearance channels. Uncertainties of all involved parameters and
statistical errors are included. We find previously ignored correlations in the
multidimensional parameter space, leading to modifications in the physics
reach, which amount in some cases to one order of magnitude. Including proper
statistical errors we determine for all parameters the improved sensitivity
limits for various baselines, beam energies, neutrino fluxes and detector
masses. Our results allow a comparison of the physics potential for different
choices of baseline and beam energy with regard to all involved parameters. In
addition we discuss in more detail the problem of parameter degeneracies in
measurements of delta_CP.Comment: 29 pages, 14 fugure
- …