Three-flavor analysis of long-baseline experiments

We compare the analysis of existing and future neutrino oscillation long-baseline experiments, where we point out that the analysis of future experiments actually implies a 12-dimensional parameter space. Within the three-flavor neutrino oscillation framework, six of these parameters are the fit parameters, and six are the simulated parameters. This high-dimensional parameter space requires the condensation of information and the definition of performance indicators for the purpose needed. As the most sophisticated example for such an indicator, we choose the precision of the leptonic CP phase, and discuss some of the complications of its computation and interpretation.Comment: Talk given at the 6th International Workshop on Neutrino Factories & Superbeams, July 26-Aug 1, 2004, Osaka, Japan. 3 page

Physics reach of β\beta-beams and ν\nu-factories: the problem of degeneracies

We discuss the physics reach of $\beta$-Beams and $\nu$-Factories from a theoretical perspective, having as a guideline the problem of degeneracies. The presence of degenerate solutions in the measure of the neutrino oscillation parameters $\theta_{13}$ and $\delta$ is, in fact, the main problem that have to be addressed in planning future neutrino oscillation experiments. If degeneracies are not (at least partially) solved, it will be almost impossible to perform, at any future facility, precise measurements of $\theta_{13}$ and/or $\delta$. After a pedagogical introduction on why degenerate solutions arise and how we can get rid of them, we analyze the physics reach of current $\beta$-beam and $\nu$-factory configurations. The physics reach of the "standard" \BB is severely affected by degeneracies while a better result can be obtained by higher-$\gamma$ setups. At the \NF the combination of Golden and Silver channels can solve the eightfold degeneracy down to $\sin^2\theta_{13} \le 10^{-3}$Comment: 5 pages, 6 epsfig; NUFACT'05, 21-26 June 2005, Frascat

CP, T and CPT violation in future long baseline experiments

I give a short overview about the possibilities and problems related to the measurement of CP violation in long baseline experiments. Special attention is paid to the issue of degeneracies and a method for their resolution is quantitatively discussed. The CP violation reach for different experiments is compared in dependence of $\sin^22\theta_{13}$ and \dm{21}. Furthermore a short comment about the possible effects of matter induced T violation is made. Finally the limits on CPT violation obtainable at a neutrino factory are shown.Comment: Talk presented at NUFACT02, London, 1-6 July, 2002. 3 pages, 2 figure

Neutrino Factory Superbeam

We discuss the optimization of a neutrino factory for large \sin^2 2 \theta_{13}, where we assume minimum effort on the accelerator side. This implies that we use low muon energies for the price of an optimized detection system. We demonstrate that such a neutrino factory performs excellent if combined with the electron neutrino appearance channel. Instead of the platinum channel operated with the muon neutrinos from the muon decays, we propose to use the initial superbeam from the decaying pions and kaons, which might be utilized at little extra effort. Since we assume out-of-phase bunches arriving at the same detector, we do not require electron charge identification. In addition, we can choose the proton energy such that we obtain a synergistic spectrum peaking at lower energies. We find that both the superbeam and the neutrino factory beam should used at the identical baseline to reduce matter density uncertainties, possibly with the same detector. This effectively makes the configuration a single experiment, which we call ``neutrino factory superbeam''. We demonstrate that this experiment outperforms a low-energy neutrino factory or a wide band beam alone beyond a simple addition of statistics.Comment: 7 pages, 5 figures, 1 tabl

Physics Reach with a Monochromatic Neutrino Beam from Electron Capture

Neutrino oscillation experiments from different sources have demonstrated non-vanishing neutrino masses and flavour mixings. The next experiments have to address the determination of the connecting mixing U(e3) and the existence of the CP violating phase. Whereas U(e3) measures the strength of the oscillation probability in appearance experiments, the CP phase acts as a phase-shift in the interference pattern. Here we propose to separate these two parameters by energy dependence, using the novel idea of a monochromatic neutrino beam facility based on the acceleration of ions that decay fast through electron capture. Fine tuning of the boosted neutrino energy allows precision measurements able to open a window for the discovery of CP violation, even for a mixing as small as 1 degree.Comment: 4 pages, 1 figure. Talk given at the International Europhysics Conference on High Energy Physics, HEP-EPS 2005, Lisbon, Portugal, July 21-27, 200

Perspectives in Neutrino Physics: Monochromatic Neutrino Beams

In the last few years spectacular results have been achieved with the demonstration of non vanishing neutrino masses and flavour mixing. The ultimate goal is the understanding of the origin of these properties from new physics. In this road, the last unknown mixing $[U_{e3}]$ must be determined. If it is proved to be non-zero, the possibility is open for Charge Conjugation-Parity (CP) violation in the lepton sector. This will require precision experiments with a very intense neutrino source. Here a novel method to create a monochromatic neutrino beam, an old dream for neutrino physics, is proposed based on the recent discovery of nuclei that decay fast through electron capture. Such nuclei will generate a monochromatic directional neutrino beam when decaying at high energy in a storage ring with long straight sections. We also show that the capacity of such a facility to discover new physics is impressive, so that fine tuning of the boosted neutrino energy allows precision measurements of the oscillation parameters even for a $[U_{e3}]$ mixing as small as 1 degree. We can thus open a window to the discovery of CP violation in neutrino oscillations.Comment: 15 pages, 7 figures. Contribution to the proceedings of GUSTAVOFEST - Symposium in Honour of Gustavo C. Branco: CP Violation and the Flavour Puzzle, Lisbon, Portugal, 19-20 July 200

Physics Potential of the SPL Super Beam

Performances of a neutrino beam generated by the CERN SPL proton driver are computed considering a 440 kton water Cerenkov detector at 130 km from the target. $\theta_{13}$ sensitivity down to $1.2^\circ$ and a $\delta$ sensitivity comparable to a Neutrino Factory, for $\theta_{13} \geq 3^\circ$, are within the reach of such a project.Comment: Invited talk at the Nufact02 Workshop, Imperial College of Science, Technology and Medicine, London, July 200

Summary of Working Group 1: Theory Part

I will summarize theoretical issues in Working Group 1 at Nufact'01. Although there may not be complete agreement yet on the exact optimum baseline $L$ and the muon energy $E_\mu$ for measurements of the CP phase at a neutrino factory, all the works done so far indicate that the optimum set ($L$, $E_\mu$) tends to be smaller than (3000km, 50GeV) if the uncertainty of the matter effect is assumed to be larger than $\pm$5% or the background fraction is much larger than $10^{-5}$.Comment: 9 pages, uses elsart.cls. Summary talk of theoretical part of WG1 at 3rd International Workshop on Neutrino Factory based on Muon Storage Rings (NuFACT'01), Tsukuba, Japan, 24-30 May 2001 . 1 references added slight modification adde

Geographical issues and physics applications of "very" long neutrino factory baselines

We discuss several potential applications of ``very'' long neutrino factory baselines, as well as potential detector locations for these applications.Comment: 2 pages, 2 figures; Talk given at the NuFact 05 workshop, June 21-26, Frascati, Ital