5,075 research outputs found
Finding the Leptonic Decay Mode of a Heavy Higgs Boson
We reanalyze the extraction of the heavy Higgs boson signal from the
Standard Model background at hadron supercolliders, taking into account revised
estimates of the top quark background. With new acceptance criteria the
detection of the signal remains viable. Requiring a forward jet-tag, a central
jet-veto, and a large relative transverse momentum of the two charged leptons
yields for one year of running at the SSC or LHC.Comment: LaTex(Revtex), 9 pages, 6 figures (available upon request),
MAD/PH/75
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 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
Rise of Kp Total Cross Section and Universality
The increase of the measured hadronic total cross sections at the highest
energies is empirically described by squared log of center-of-mass energy sqrt
s as sigma(tot)= B (log s)2, consistent with the energy dependence of the
Froissart unitarity bound. The coefficient B is argued to have a universal
value, but this is not proved directly from QCD. In the previous tests of this
universality, the p(pbar)p, pi p, and K p forward scatterings were analyzed
independently and found to be consistent with B(pp) = B(pip) = B(Kp), although
the determined value of B(Kp) had large uncertainty. In the present work, we
have further analyzed forward Kp scattering to obtain a more exact value of
B(Kp). Making use of continuous moment sum rules(CMSR) we have fully exploited
the information of low-energy scattering data to predict the high-energy
behavior of the amplitude hrough duality. The estimation of B(Kp) is improved
remarkably, and our result strongly supports the universality of B.Comment: 12 pages, 3 figure
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
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
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
- …