Neutrino Factories and the "Magic" Baseline

We show that for a neutrino factory baseline of $L \sim 7300 km - 7 600 km$ a ``clean'' measurement of $\sin^2 2 \theta_{13}$ becomes possible, which is almost unaffected by parameter degeneracies. We call this baseline "magic" baseline, because its length only depends on the matter density profile. For a complete analysis, we demonstrate that the combination of the magic baseline with a baseline of 3000 km is the ideal solution to perform equally well for the $\sin^2 2 \theta_{13}$, sign of $\Delta m_{31}^2$, and CP violation sensitivities. Especially, this combination can very successfully resolve parameter degeneracies even below $\sin^2 2 \theta_{13} < 10^{-4}$.Comment: Minor changes, final version to appear in PRD, 4 pages, 3 figures, RevTe

Non-standard Hamiltonian effects on neutrino oscillations

We investigate non-standard Hamiltonian effects on neutrino oscillations, which are effective additional contributions to the vacuum or matter Hamiltonian. Since these effects can enter in either flavor or mass basis, we develop an understanding of the difference between these bases representing the underlying theoretical model. In particular, the simplest of these effects are classified as ``pure'' flavor or mass effects, where the appearance of such a ``pure'' effect can be quite plausible as a leading non-standard contribution from theoretical models. Compared to earlier studies investigating particular effects, we aim for a top-down classification of a possible ``new physics'' signature at future long-baseline neutrino oscillation precision experiments. We develop a general framework for such effects with two neutrino flavors and discuss the extension to three neutrino flavors, as well as we demonstrate the challenges for a neutrino factory to distinguish the theoretical origin of these effects with a numerical example. We find how the precision measurement of neutrino oscillation parameters can be altered by non-standard effects alone (not including non-standard interactions in the creation and detection processes) and that the non-standard effects on Hamiltonian level can be distinguished from other non-standard effects (such as neutrino decoherence and decay) if we consider specific imprint of the effects on the energy spectra of several different oscillation channels at a neutrino factory.Comment: 30 pages, 6 figures, LaTeX, final version, published in Eur.Phys.J.

Effects of new physics in neutrino oscillations in matter

A new flavor changing electron neutrino interaction with matter would always dominate the nu_e oscillation probability at sufficiently high neutrino energies. Being suppressed by theta_{13}, the energy scale at which the new effect starts to be relevant may be within the reach of realistic experiments, where the peculiar dependence of the signal with energy could give rise to a clear signature in the nu_e --> nu_tau channel. The latter could be observed by means of a coarse large magnetized detector by exploiting tau --> mu decays. We discuss the possibility of identifying or constraining such effects with a high energy neutrino factory. We also comment on the model independent limits on them.Comment: 11 pages, 5 figure

Reexamining nonstandard interaction effects on supernova neutrino flavor oscillations

Several extensions of the standard electroweak model allow new four-fermion interactions (nu_a nu_b * ff) with strength eps_ab*G_F, where (a,b) are flavor indices. We revisit their effects on flavor oscillations of massive (anti)neutrinos in supernovae, in order to achieve, in the region above the protoneutron star, an analytical treatment valid for generic values of the neutrino mixing angles (omega,phi,psi)=(theta_12,theta_13,theta_23). Assuming that eps_ab<<1, we find that the leading effects on the flavor transitions occurring at high (H) and low (L) density along the supernova matter profile can be simply embedded through the replacements phi-->phi+eps_H and omega-->omega+eps_L, respectively, where eps_H and eps_L are specific linear combinations of the eps_ab's. Similar replacements hold for eventual oscillations in the Earth matter. From a phenomenological point of view, the most relevant consequence is a possible uncontrolled bias (phi-->phi+eps_H) in the value of the mixing angle phi inferred by inversion of supernova neutrino data. Such a drawback, however, does not preclude the discrimination of the neutrino mass spectrum hierarchy (direct or inverse) through supernova neutrino oscillations.Comment: Text clarified, one figure added. To appear in PR

The role of matter density uncertainties in the analysis of future neutrino factory experiments

Matter density uncertainties can affect the measurements of the neutrino oscillation parameters at future neutrino factory experiments, such as the measurements of the mixing parameters $\theta_{13}$ and \deltacp. We compare different matter density uncertainty models and discuss the possibility to include the matter density uncertainties in a complete statistical analysis. Furthermore, we systematically study in which measurements and where in the parameter space matter density uncertainties are most relevant. We illustrate this discussion with examples that show the effects as functions of different magnitudes of the matter density uncertainties. We find that matter density uncertainties are especially relevant for large \stheta \gtrsim 10^{-3}. Within the KamLAND-allowed range, they are most relevant for the precision measurements of \stheta and \deltacp, but less relevant for ``binary'' measurements, such as for the sign of \ldm, the sensitivity to \stheta, or the sensitivity to maximal CP violation. In addition, we demonstrate that knowing the matter density along a specific baseline better than to about 1% precision means that all measurements will become almost independent of the matter density uncertainties.Comment: 21 pages, 7 figures, LaTeX. Final version to be published in Phys. Rev.

Solar neutrino oscillation parameters after first KamLAND results

We analyze the energy spectrum of reactor neutrino events recently observed in the Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) and combine them with solar and terrestrial neutrino data, in the context of two- and three-family active neutrino oscillations. In the 2-neutrino case, we find that the solution to the solar neutrino problem at large mixing angle (LMA) is basically split into two sub-regions, that we denote as LMA-I and LMA-II. The LMA-I solution, characterized by lower values of the squared neutrino mass gap, is favored by the global data fit. This picture is not significantly modified in the 3-neutrino mixing case. A brief discussion is given about the discrimination of the LMA-I and LMA-II solutions with future KamLAND data. In both the 2- and 3-neutrino cases, we present a detailed analysis of the post-KamLAND bounds on the oscillation parameters.Comment: Revised version. Two figures adde

Clone flow analysis for a theory inspired Neutrino Experiment planning

The presence of several clone solutions in the simultaneous measurement of ($\theta_{13},\delta$) has been widely discussed in literature. In this letter we write the analytical formulae of the clones location in the ($\theta_{13},\delta$) plane as a function of the physical input pair ($\bar\theta_{13},\bar\delta$). We show how the clones move with changing $\bar\theta_{13}$. The "clone flow" can be significantly different if computed (naively) from the oscillation probabilities or (exactly) from the probabilities integrated over the neutrino flux and cross-section. Using our complete computation we compare the clone flow of a set of possible future neutrino experiments: the CERN SuperBeam, BetaBeam and Neutrino Factory proposals. We show that the combination of these specific BetaBeam and SuperBeam does not help in solving the degeneracies. On the contrary, the combination of one of them with the Neutrino Factory Golden and Silver channel can be used, from a theoretical point of view, to solve completely the eightfold degeneracy.Comment: 23 pages, using epsfi

Precision Neutrino Oscillation Physics with an Intermediate Baseline Reactor Neutrino Experiment

We discuss the physics potential of intermediate $L \sim 20 \div 30$ km baseline experiments at reactor facilities, assuming that the solar neutrino oscillation parameters $\Delta m^2_{\odot}$ and $\theta_{\odot}$ lie in the high-LMA solution region. We show that such an intermediate baseline reactor experiment can determine both $\Delta m^2_{\odot}$ and $\theta_{\odot}$ with a remarkably high precision. We perform also a detailed study of the sensitivity of the indicated experiment to $\Delta m^2_{\rm atm}$, which drives the dominant atmospheric $\nu_{\mu}$ ($\bar{\nu}_{\mu}$) oscillations, and to $\theta$ - the neutrino mixing angle limited by the data from the CHOOZ and Palo Verde experiments. We find that this experiment can improve the bounds on $\sin^2\theta$. If the value of $\sin^2\theta$ is large enough, \sin^2\theta \gtap 0.02, the energy resolution of the detector is sufficiently good and if the statistics is relatively high, it can determine with extremely high precision the value of $\Delta m^2_{\rm atm}$. We also explore the potential of the intermediate baseline reactor neutrino experiment for determining the type of the neutrino mass spectrum, which can be with normal or inverted hierarchy. We show that the conditions under which the type of neutrino mass hierarchy can be determined are quite challenging, but are within the reach of the experiment under discussion.Comment: 25 page

Atmospheric Neutrino Oscillations and New Physics

We study the robustness of the determination of the neutrino masses and mixing from the analysis of atmospheric and K2K data under the presence of different forms of phenomenologically allowed new physics in the nu_mu--nu_tau sector. We focus on vector and tensor-like new physics interactions which allow us to treat, in a model independent way, effects due to the violation of the equivalence principle, violations of the Lorentz invariance both CPT conserving and CPT violating, non-universal couplings to a torsion field and non-standard neutrino interactions with matter. We perform a global analysis of the full atmospheric data from SKI together with long baseline K2K data in the presence of nu_mu -> nu_tau transitions driven by neutrino masses and mixing together with sub-dominant effects due to these forms of new physics. We show that within the present degree of experimental precision, the extracted values of masses and mixing are robust under those effects and we derive the upper bounds on the possible strength of these new interactions in the nu_mu--nu_tau sector.Comment: 22 pages, LaTeX file using RevTEX4, 5 figures and 4 tables include

A minimal Beta Beam with high-Q ions to address CP violation in the leptonic sector

In this paper we consider a Beta Beam setup that tries to leverage at most existing European facilities: i.e. a setup that takes advantage of facilities at CERN to boost high-Q ions (8Li and 8B) aiming at a far detector located at L = 732 Km in the Gran Sasso Underground Laboratory. The average neutrino energy for 8Li and 8B ions boosted at \gamma ~ 100 is in the range E_\nu = [1,2] GeV, high enough to use a large iron detector of the MINOS type at the far site. We perform, then, a study of the neutrino and antineutrino fluxes needed to measure a CP-violating phase delta in a significant part of the parameter space. In particular, for theta_13 > 3 deg, if an antineutrino flux of 3 10^19 useful 8Li decays per year is achievable, we find that delta can be measured in 60% of the parameter space with 6 10^18 useful 8B decays per year.Comment: 19 pages, 10 figures, added references and corrected typo