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 $2\times 2$ 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 $L/E$, 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 51^{51}Cr Source Experiment

The recent result from the chromium source experiment carried out by the GALLEX collaboration implies interesting limits on the parameters $\Delta m^2$ and $\sin^22\theta$ describing neutrino oscillations. Values of $\Delta m^2~>~0.17$ eV$^2$ for maximal mixing and of $\sin^22\theta > 0.38$ for $\Delta m^2 > 1$~eV$^2$ are ruled out at 90\% C.L. This result improves by more than an order of magnitude previous limits on $\Delta m^2$ 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 $10^{-2}$, 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

Associated Charm Production in Neutrino-Nucleus Interactions

In this paper a search for associated charm production both in neutral and charged current $\nu$-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 $\nu$ 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 0.18$\pm$0.05. The relative rate of the associated charm cross-section in deep inelastic $\nu$ interactions, $\sigma(c\bar{c}\nu)/\sigma_\mathrm{NC}^\mathrm{DIS}= (3.62^{+2.95}_{-2.42}({stat})\pm 0.54({syst}))\times 10^{-3}$ has been measured. One event with two charm decays has been observed in charged-current $\nu_\mu$ interactions with an estimated background of 0.18$\pm$0.06 and the upper limit on associated charm production in charged-current interactions at 90% C.L. has been found to be $\sigma (c\bar{c} \mu^-)/\sigma_\mathrm{CC} < 9.69 \times 10^{-4}$.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 ${\cal O}(10^{4\sim 6})$ 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