345 research outputs found
Immittance Matching for Multi-dimensional Open-system Photonic Crystals
An electromagnetic (EM) Bloch wave propagating in a photonic crystal (PC) is
characterized by the immittance (impedance and admittance) of the wave. The
immittance is used to investigate transmission and reflection at a surface or
an interface of the PC. In particular, the general properties of immittance are
useful for clarifying the wave propagation characteristics. We give a general
proof that the immittance of EM Bloch waves on a plane in infinite one- and
two-dimensional (2D) PCs is real when the plane is a reflection plane of the PC
and the Bloch wavevector is perpendicular to the plane. We also show that the
pure-real feature of immittance on a reflection plane for an infinite
three-dimensional PC is good approximation based on the numerical calculations.
The analytical proof indicates that the method used for immittance matching is
extremely simplified since only the real part of the immittance function is
needed for analysis without numerical verification. As an application of the
proof, we describe a method based on immittance matching for qualitatively
evaluating the reflection at the surface of a semi-infinite 2D PC, at the
interface between a semi-infinite slab waveguide (WG) and a semi-infinite 2D PC
line-defect WG, and at the interface between a semi-infinite channel WG and a
semi-infinite 2D PC slab line-defect WG.Comment: 8 pages, 6 figure
A Quasi-maximal mixing ansatz for neutrino oscillations
Inspired by the atmospheric multi-GeV neutrino data, we consider neutrino
flavor mixing matrices which are maximal in a subsector. This
condition is a strong restriction: the full matrix including complex phases
depends essentially on one parameter. The survival probability is an universal
function of , independent of generation, in the region of interest for the
accelerator and atmospheric experiments. It is possible with the solar neutrino
data alone to recover completely the mixing matrix suggested by the atmospheric
data. The results are not essentially modified by the MSW effect in the solar
data. Consequences for future experiments are considered.Comment: 12 latex pages, 2 fig in 2 ps files (uuencoded). full ps avalaible at
http://www-itp.unibe.ch/~torrente/pap6.ps In this revised version: some
mistakes corrected, new subcases (quasi-maximal mixing e-\mu, e-\tau) studie
Limits on Electron-Neutrino Oscillations from the GALLEX Cr Source Experiment
The recent result from the chromium source experiment carried out by the
GALLEX collaboration implies interesting limits on the parameters
and describing neutrino oscillations. Values of eV for maximal mixing and of for ~eV are ruled out at 90\% C.L. This result improves by more than an
order of magnitude previous limits on derived from
electron-neutrino oscillation experiments at accelerators.Comment: 6 pages (REVTEX) + one figure (postscript), all in uuencoded forma
Experimental Constraints on the Neutrino Oscillations and a Simple Model of Three Flavour Mixing
A simple model of the neutrino mixing is considered, which contains only one
right-handed neutrino field, coupled via the mass term to the three usual
left-handed fields. This is a simplest model that allows for three-flavour
neutrino oscillations. The existing experimental limits on the neutrino
oscillations are used to obtain constraints on the two free mixing parameters
of the model. A specific sum rule relating the oscillation probabilities of
different flavours is derived.Comment: 10 pages, 3 figures in post script, Latex, IFT 2/9
Is CP Violation Observable in Long Baseline Neutrino Oscillation Experiments ?
We have studied CP violation originated by the phase of the neutrino mixing
matrix in the long baseline neutrino oscillation experiments. The direct
measurements of CP violation is the difference of the transition probabilities
between CP-conjugate channels. In those experiments, the CP violating effect is
not suppressed if the highest neutrino mass scale is taken to be 1\sim 5 \eV,
which is appropriate for the cosmological hot dark matter. Assuming the
hierarchy for the neutrino masses, the upper bounds of CP violation have been
caluculated for three cases, in which mixings are constrained by the recent
short baseline ones. The calculated upper bounds are larger than ,
which will be observable in the long baseline accelerator experiments. The
matter effect, which is not CP invariant, has been also estimated in those
experiments.Comment: 28 pages, LaTex file, 6 figures included using epsfig Matter effect
is estimated(Figs.3(a) (b)). Physical parameters are change
Muon-anti-neutrino <---> electron-anti-neutrino mixing: analysis of recent indications and implications for neutrino oscillation phenomenology
We reanalyze the recent data from the Liquid Scintillator Neutrino Detector
(LSND) experiment, that might indicate anti-nu_muanti-nu_e mixing. This
indication is not completely excluded by the negative results of established
accelerator and reactor neutrino oscillation searches. We quantify the region
of compatibility by means of a thorough statistical analysis of all the
available data, assuming both two-flavor and three-flavor neutrino
oscillations. The implications for various theoretical scenarios and for future
oscillation searches are studied. The relaxation of the LSND constraints under
different assumptions in the statistical analysis is also investigated.Comment: 17 pages (RevTeX) + 9 figures (Postscript) included with epsfig.st
Embedding technology in translation teaching:evaluative considerations for courseware integration
Associated Charm Production in Neutrino-Nucleus Interactions
In this paper a search for associated charm production both in neutral and
charged current -nucleus interactions is presented. The improvement of
automatic scanning systems in the {CHORUS} experiment allows an efficient
search to be performed in emulsion for short-lived particles. Hence a search
for rare processes, like the associated charm production, becomes possible
through the observation of the double charm-decay topology with a very low
background. About 130,000 interactions located in the emulsion target
have been analysed. Three events with two charm decays have been observed in
the neutral-current sample with an estimated background of 0.180.05. The
relative rate of the associated charm cross-section in deep inelastic
interactions, has been
measured. One event with two charm decays has been observed in charged-current
interactions with an estimated background of 0.180.06 and the
upper limit on associated charm production in charged-current interactions at
90% C.L. has been found to be .Comment: 10 pages, 4 figure
Accelerator and Reactor Neutrino Oscillation Experiments in a Simple Three-Generation Framework
We present a new approach to the analysis of neutrino oscillation
experiments, in the one mass-scale limit of the three-generation scheme. In
this framework we reanalyze and recombine the most constraining accelerator and
reactor data, in order to draw precise bounds in the new parameter space. We
consider our graphical representations as particularly suited to show the
interplay among the different oscillation channels. Within the same framework,
the discovery potential of future short and long baseline experiments is also
investigated, in the light of both the recent signal from the LSND experiment
and the atmospheric neutrino anomaly.Comment: uuencoded compressed tar file. Figures (13) available by ftp to
ftp://eku.sns.ias.edu/pub/lisi/ (192.16.204.30). Submitted to Physical Review
Natural Neutrino Mass Matrix
Naturalness of the neutrino mass hierarchy and mixing is studied. First we
select among 12 neutrino mixing patterns a few patterns, which could form the
natural neutrino mass matrix. Further we show that if the Dirac neutrino mass
matrix is taken as the natural one in the quark sector, then only two mixing
patterns without the large mixing lead to the natural right-handed Majorana
mass matrix. The rest of the chosen patterns with three degenerate mass
solution lead to the unnatural right-handed Majorana mass matrix in the see-saw
mechanism. Notice however, that for the chosen two natural patterns there could
be a huge mass hierarchy such as in order to reproduce
the inverse mass hierarchy of the light neutrinos.Comment: 31 pages, LaTex file, no figures, arguments made more clear, main
conclusions unchanged, version accepted for publication in PRD Reort-no:
Lund-Mph-97/14 Revise
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