Measuring CP violation and mass ordering in joint long baseline experiments with superbeams

We propose to measure the CP phase $\delta_{\rm CP}$, the magnitude of the neutrino mixing matrix element $|U_{e3}|$ and the sign of the atmopheric scale mass--squared difference $\Delta{\rm m}^2_{31}$ with a superbeam by the joint analysis of two different long baseline neutrino oscillation experiments. One is a long baseline experiment (LBL) at 300 km and the other is a very long baseline (VLBL) experiment at 2100 km. We take the neutrino source to be the approved high intensity proton synchrotron, HIPA. The neutrino beam for the LBL is the 2-degree off-axis superbeam and for the VLBL, a narrow band superbeam. Taking into account all possible errors, we evaluate the event rates required and the sensitivities that can be attained for the determination of $\delta_{\rm CP}$ and the sign of $\Delta m^2_{31}$. We arrive at a representative scenario for a reasonably precise probe of this part of the neutrino physics.Comment: 25 RevTEX pages, 16 PS figures, revised figure captions and references adde

Short-Baseline Neutrino Oscillations at a Neutrino Factory

Within the framework of three-neutrino and four-neutrino scenarios that can describe the results of the LSND experiment, we consider the capabilities of short baseline neutrino oscillation experiments at a neutrino factory. We find that, when short baseline (L \alt 100 km) neutrino factory measurements are used together with other accelerator-based oscillation results, the complete three-neutrino parameter space can best be determined by measuring the rate of $\nu_e \to \nu_\tau$ oscillations, and measuring CP violation with either $\nu_e \to \nu_\mu$ or $\nu_\mu \to \nu_\tau$ oscillations (including the corresponding antineutrino channels). With measurements of CP violation in both $\nu_e \to \nu_\mu$ and $\nu_\mu \to \nu_\tau$ it may be possible to distinguish between the three- and four-neutrino cases.Comment: 16 pages, Revtex (single-spaced), 8 postscript figures, uses epsf.st

Long Baseline Neutrino Physics with a Muon Storage Ring Neutrino Source

We examine the physics capabilities of known flavor neutrino beams from intense muon sources. We find that long-baseline neutrino experiments based on such beams can provide precise measurements of neutrino oscillation mass and mixing parameters. Furthermore, they can test whether the dominant atmospheric neutrino oscillations are \nu_\mu --> \nu_\tau and/or \nu_\mu --> \nu_s, determine the \nu_\mu --> \nu_e content of atmospheric neutrino oscillations, and measure \nu_e --> \nu_\tau appearance. Depending on the oscillation parameters, they may be able to detect Earth matter and CP violation effects and to determine the ordering of some of the mass eigenstates.Comment: 38 pages, Revtex with epsf.sty, 21 postscript figures. Minor text revisions, some new numbers in Tables II and II

Damping signatures in future neutrino oscillation experiments

We discuss the phenomenology of damping signatures in the neutrino oscillation probabilities, where either the oscillating terms or the probabilities can be damped. This approach is a possibility for tests of non-oscillation effects in future neutrino oscillation experiments, where we mainly focus on reactor and long-baseline experiments. We extensively motivate different damping signatures due to small corrections by neutrino decoherence, neutrino decay, oscillations into sterile neutrinos, or other mechanisms, and classify these signatures according to their energy (spectral) dependencies. We demonstrate, at the example of short baseline reactor experiments, that damping can severely alter the interpretation of results, e.g., it could fake a value of $\sin(2\theta_{13})$ smaller than the one provided by Nature. In addition, we demonstrate how a neutrino factory could constrain different damping models with emphasis on how these different models could be distinguished, i.e., how easily the actual non-oscillation effects could be identified. We find that the damping models cluster in different categories, which can be much better distinguished from each other than models within the same cluster.Comment: 33 pages, 5 figures, LaTeX. Final version published in JHE

Oscillation enhanced search for new interaction with neutrinos

We discuss the measurement of new physics in long baseline neutrino oscillation experiments. Through the neutrino oscillation, the probability to detect the new physics effects such as flavor violation is enhanced by the interference with the weak interaction. We carefully explain the situations that the interference can take place. Assuming a neutrino factory and an upgraded conventional beam, we estimate the feasibility to observe new physics numerically and point out that we can search new interactions using some channels, for example $\nu_{\mu} \to \nu_{\mu}$, in these experiments. We also discuss several models which induce the effective interactions interfering with the weak interaction, and show that some new physics effects are large enough to be observed in the oscillation enhanced way.Comment: 25 pages, 20 figure

Supersymmetry and a rationale for small CP violating phases

We analyse the CP problem in the context of a supersymmetric extension of the standard model with universal strength of Yukawa couplings. A salient feature of these models is that the CP phases are constrained to be very small by the hierarchy of the quark masses, and the pattern of CKM mixing angles. This leads to a small amount of CP violation from the usual KM mechanism and a significant contribution from supersymmetry is required. Due to the large generation mixing in some of the supersymmetric interactions, the electric dipole moments impose severe constraints on the parameter space, forcing the trilinear couplings to be factorizable in matrix form. We find that the LL mass insertions give the dominant gluino contribution to saturate epsilon_K. The chargino contributions to epsilon'/epsilon are significant and can accommodate the experimental results. In this framework, the standard model gives a negligible contribution to the CP asymmetry in B-meson decay, a_{J/\psi K_s}. However, due to supersymmetric contributions to B_d-\bar{B}_d mixing, the recent large value of a_{J/\psi K_s} can be accommodated.Comment: 30 pages, 5 figures. Version to appear in Nucl. Phys.

Seesaw tau lepton mass and calculable neutrino masses in a 3-3-1 model

In a version of the 3-3-1 model proposed by Duong and Ma the introduction of the scalar sextet for giving mass to the charged leptons is avoided by adding a singlet charged lepton. We show that in this case the $\tau$ lepton gains mass through a seesaw--like mechanism. Besides we show how to generate neutrino masses at the tree and at the 1-loop level with the respective Maki-Nakagawa-Sakata leptonic mixing matrices.Comment: revtex, 5 pages and one eps figure. Published versio

Status of atmospheric neutrino(mu)<-->neutrino(tau) oscillations and decoherence after the first K2K spectral data

We review the status of nu_mu-->nu_tau flavor transitions of atmospheric neutrinos in the 92 kton-year data sample collected in the first phase of the Super-Kamiokande (SK) experiment, in combination with the recent spectral data from the KEK-to-Kamioka (K2K) accelerator experiment (including 29 single-ring muon events). We consider a theoretical framework which embeds flavor oscillations plus hypothetical decoherence effects, and where both standard oscillations and pure decoherence represent limiting cases. It is found that standard oscillations provide the best description of the SK+K2K data, and that the associated mass-mixing parameters are determined at 1 sigma (and d.o.f.=1) as: Delta m^2=(2.6 +- 0.4)x10^{-3} eV^2 and sin^2(2theta)=1.00+0.00-0.05. As compared with standard oscillations, the case of pure decoherence is disfavored, although it cannot be ruled out yet. In the general case, additional decoherence effects in the nu_mu-->nu_tau channel do not improve the fit to the SK and K2K data, and upper bounds can be placed on the associated decoherence parameter. Such indications, presently dominated by SK, could be strengthened by further K2K data, provided that the current spectral features are confirmed with higher statistics. A detailed description of the statistical analysis of SK and K2K data is also given, using the so-called ``pull'' approach to systematic uncertainties.Comment: 18 pages (RevTeX) + 12 figures (PostScript

Modeling realistic Earth matter density for CP violation in neutrino oscillation

We examine the effect of a more realistic Earth matter density model which takes into account of the local density variations along the baseline of a possi ble 2100 km very long baseline neutrino oscillation experiment. Its influence to the measurement of CP violation is investigated and a comparison with the commonly used global density models made. Significant differences are found in the comparison of the results of the different density models.Comment: 16 pages, 8 figure

CP violating neutrino oscillation and uncertainties in Earth matter density

We propose a statistical formulation to estimate possible errors in long baseline neutrino oscillation experiments caused by uncertainties in the Earth matter density. A quantitative investigation of the effect is made on the CP asymmetry in future neutrino factory experiments.Comment: Latex, 10 pages, 5 figure