ν−K0\nu - K^0 Analogy, Dirac-Majorana Neutrino Duality and the Neutrino Oscillations

The intent of this paper is to convey a new primary physical idea of a Dirac-Majorana neutrino duality in relation to the topical problem of neutrino oscillations. In view of the new atmospheric, solar and the LSND neutrino oscillation data, the Pontecorvo $\nu - K^0$ oscillation analogy is generalized to the notion of neutrino duality with substantially different physical meaning ascribed to the long-baseline and the short-baseline neutrino oscillations. At the level of CP-invariance, the suggestion of dual neutrino properties defines the symmetric two-mixing-angle form of the widely discussed four-neutrino $(2+2)$-mixing scheme, as a result of the lepton charge conservation selection rule and a minimum of two Dirac neutrino fields. With neutrino duality, the two-doublet structure of the Majorana neutrino mass spectrum is a vestige of the two-Dirac-neutrino origin. The fine neutrino mass doublet structure is natural because it is produced by a lepton charge symmetry violating perturbation on a zero-approximation system of two twofold mass-degenerate Dirac neutrino-antineutrino pairs. A set of inferences related to the neutrino oscillation phenomenology in vacuum is considered.Comment: 13 pages, LaTeX. Minor modifications, new references adde

Probing the Planck Scale with Neutrino Oscillations

Quantum gravity "foam", among its various generic Lorentz non-invariant effects, would cause neutrino mixing. It is shown here that, if the foam is manifested as a nonrenormalizable effect at scale M, the oscillation length generically decreases with energy $E$ as (E/M)^(-2). Neutrino observatories and long-baseline experiments should have therefore already observed foam-induced oscillations, even if M is as high as the Planck energy scale. The null results, which can be further strengthened by better analysis of current data and future experiments, can be taken as experimental evidence that Lorentz invariance is fully preserved at the Planck scale, as is the case in critical string theory.Comment: 11 pages, 2 figures. Final version published in PRD. 1 figure, references, clarifications and explanations added. Results unchange

Renaissance of the ~1 TeV Fixed-Target Program

This document describes the physics potential of a new fixed-target program based on a ~1 TeV proton source. Two proton sources are potentially available in the future: the existing Tevatron at Fermilab, which can provide 800 GeV protons for fixed-target physics, and a possible upgrade to the SPS at CERN, called SPS+, which would produce 1 TeV protons on target. In this paper we use an example Tevatron fixed-target program to illustrate the high discovery potential possible in the charm and neutrino sectors. We highlight examples which are either unique to the program or difficult to accomplish at other venues.Comment: 31 pages, 11 figure

CP violation effect in long-baseline neutrino oscillation in the four-neutrino model

We investigate CP-violation effect in the long-baseline neutrino oscillation in the four-neutrino model with mass scheme of the two nearly degenerate pairs separated with the order of 1 eV, by using the data from the solar neutrino deficit, the atmospheric neutrino anomaly and the LSND experiments along with the other accelerator and reactor experiments. By use of the most general parametrization of the mixing matrix with six angles and six phases, we show that the genuine CP-violation effect could attain as large as 0.3 for $\Delta P(\nu_\mu\to\nu_\tau) \equiv P(\nu_\mu\to\nu_\tau) - P(\bar{\nu_\mu}\to\bar{\nu_\tau})$ and that the matter effect is negligibly small such as at most 0.01 for $\Delta P(\nu_\mu\to\nu_\tau)$ for $\Delta m^2 = (1-5)\times 10^{-3} {\rm eV}^2$, which is the mass-squared difference relevant to the long-baseline oscillation.Comment: 21 pages in LaTeX, 9 ps figures. Some changes in the Introduction and Reference

New physics searches at near detectors of neutrino oscillation experiments

We systematically investigate the prospects of testing new physics with tau sensitive near detectors at neutrino oscillation facilities. For neutrino beams from pion decay, from the decay of radiative ions, as well as from the decays of muons in a storage ring at a neutrino factory, we discuss which effective operators can lead to new physics effects. Furthermore, we discuss the present bounds on such operators set by other experimental data currently available. For operators with two leptons and two quarks we present the first complete analysis including all relevant operators simultaneously and performing a Markov Chain Monte Carlo fit to the data. We find that these effects can induce tau neutrino appearance probabilities as large as O(10^{-4}), which are within reach of forthcoming experiments. We highlight to which kind of new physics a tau sensitive near detector would be most sensitive.Comment: 20 pages, 2 figures, REVTeX

Probing possible decoherence effects in atmospheric neutrino oscillations

It is shown that the results of the Super-Kamiokande atmospheric neutrino experiment, interpreted in terms of nu_munu_tau flavor transitions, can probe possible decoherence effects induced by new physics (e.g., by quantum gravity) with high sensitivity, supplementing current laboratory tests based on kaon oscillations and on neutron interferometry. By varying the (unknown) energy dependence of such effects, one can either obtain strong limits on their amplitude, or use them to find an unconventional solution to the atmospheric nu anomaly based solely on decoherence.Comment: Title changed; major changes in the text; includes the discussion of a new solution to the atmosheric neutrino anomaly, based on decoherence; a second figure and a note have been adde

Leading order analysis of neutrino induced dimuon events in the CHORUS experiment

We present a leading order QCD analysis of a sample of neutrino induced charged-current events with two muons in the final state originating in the lead-scintillating fibre calorimeter of the CHORUS detector. The results are based on a sample of 8910 neutrino and 430 antineutrino induced opposite-sign dimuon events collected during the exposure of the detector to the CERN Wide Band Neutrino Beam between 1995 and 1998. % with $E_{\mu 1},E_{\mu 2} > 5$ GeV and $Q^2 > 3$ GeV$^2$ collected %between 1995 and 1998. The analysis yields a value of the charm quark mass of \mc = (1.26\pm 0.16 \pm 0.09) \GeVcc and a value of the ratio of the strange to non-strange sea in the nucleon of $\kappa = 0.33 \pm 0.05 \pm 0.05$, improving the results obtained in similar analyses by previous experiments.Comment: Submitted to Nuclear Physics

Final NOMAD results on nu_mu->nu_tau and nu_e->nu_tau oscillations including a new search for nu_tau appearance using hadronic tau decays

Results from the nu_tau appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic tau decays, significantly improving the overall sensitivity of the experiment to oscillations. The "blind analysis" of all topologies yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90% C.L. allowed region in the sin^2(2theta)-Delta m^2 plane which includes sin^2(2theta)<3.3 x 10^{-4} at large Delta m^2 and Delta m^2 < 0.7 eV^2/c^4 at sin^2(2theta)=1. The corresponding contour in the nu_e->nu_tau oscillation hypothesis results in sin^2(2theta)<1.5 x 10^{-2} at large Delta m^2 and Delta m^2 < 5.9 eV^2/c^4 at sin^2(2theta)=1. We also derive limits on effective couplings of the tau lepton to nu_mu or nu_e.Comment: 46 pages, 16 figures, Latex, to appear on Nucl. Phys.

Confusing non-standard neutrino interactions with oscillations at a neutrino factory

Most neutrino mass theories contain non-standard interactions (NSI) of neutrinos which can be either non-universal (NU) or flavor-changing (FC). We study the impact of such interactions on the determination of neutrino mixing parameters at a neutrino factory using the so-called ``golden channels'' \pnu{e}\to\pnu{\mu} for the measurement of \theta_{13}. We show that a certain combination of FC interactions in neutrino source and earth matter can give exactly the same signal as oscillations arising due to \theta_{13}. This implies that information about \theta_{13} can only be obtained if bounds on NSI are available. Taking into account the existing bounds on FC interactions, this leads to a drastic loss in sensitivity in \theta_{13}, at least two orders of magnitude. A near detector at a neutrino factory offers the possibility to obtain stringent bounds on some NSI parameters. Such near site detector constitutes an essential ingredient of a neutrino factory and a necessary step towards the determination of \theta_{13} and subsequent study of leptonic CP violation.Comment: 23 pages, 5 figures, improved version, accepted for publication in Phs. Rev. D, references adde