arXiv subjects

E. Fernandez-Martinez

Publications and source records attributed to E. Fernandez-Martinez.

27 records · Page 2Linked to original sources

arXiv2007

Neutrino hierarchy from CP-blind observables with high density magnetized detectors

High density magnetized detectors are well suited to exploit the outstanding purity and intensities of novel neutrino sources like Neutrino Factories and Beta Beams. They can also provide independent measurements of leptonic mixing parameters through the observation of atmospheric muon-neutrinos. In this paper, we discuss the combination of these observables from a multi-kton iron detector and a high energy Beta Beam; in particular, we demonstrate that even with moderate detector granularities the neutrino mass hierarchy can be determined for $θ_{13}$ values greater than 4$^\circ$.

hep-ph↗

arXiv2007

CP-violation from non-unitary leptonic mixing

A low-energy non-unitary leptonic mixing matrix is a generic effect of a large class of theories accounting for neutrino masses. It is shown how the extra CP-odd phases of a general non-unitary matrix allow for sizeable CP-asymmetries in channels other than those dominant in the standard unitary case. The $ν_μ\to ν_τ$ channel turns out to be an excellent tool to further constrain moduli and phases. Furthermore, we clarify the relationship between our approach and the so-called "non-standard neutrino interactions" schemes: the sensitivities explored here apply as well to such constructions.

hep-ph↗

arXiv2007

Unitarity of the Leptonic Mixing Matrix

We determine the elements of the leptonic mixing matrix, without assuming unitarity, combining data from neutrino oscillation experiments and weak decays. To that end, we first develop a formalism for studying neutrino oscillations in vacuum and matter when the leptonic mixing matrix is not unitary. To be conservative, only three light neutrino species are considered, whose propagation is generically affected by non-unitary effects. Precision improvements within future facilities are discussed as well.

hep-ph↗

arXiv2006

Alternating ions in a $β$-beam to solve degeneracies

We study how the eightfold-degeneracy in the ($θ_{13},δ$) plane observed in $γ\sim 100$ $β$-beams can be reduced by periodically changing the ions in the storage ring. This ``ions cocktail'' allows to change the neutrino energy, at fixed $γ$, by choosing ions with different decay energies. We propose to combine the standard $^6$He and $^{18}$Ne beams with $^8$Li and $^8$B ones. These latter two ions have peaked $ν_e \to ν_μ$ oscillation probabilities for $γ= 100$ at a baseline $L \sim 700$ Km. At this distance and this $γ$ the oscillation probability of $^6$He and $^{18}$Ne neutrinos is at its second maximum. This setup is particularly suited for large enough values of $θ_{13}$ (within reach at T2K-I) and it allows solving most of the eightfold-degeneracy, measuring $θ_{13}, δ$ and the sign of the atmospheric mass difference for values of $θ_{13} \geq 5^\circ$.

hep-ph↗

arXiv2006

A Beta Beam complex based on the machine upgrades for the LHC

The Beta Beam CERN design is based on the present LHC injection complex and its physics reach is mainly limited by the maximum rigidity of the SPS. In fact, some of the scenarios for the machine upgrades of the LHC, particularly the construction of a fast cycling 1 TeV injector (``Super-SPS''), are very synergic with the construction of a higher $γ$ Beta Beam. At the energies that can be reached by this machine, we demonstrate that dense calorimeters can already be used for the detection of $ν$ at the far location. Even at moderate masses (40 kton) as the ones imposed by the use of existing underground halls at Gran Sasso, the CP reach is very large for any value of $θ_{13}$ that would provide evidence of $ν_e$ appearance at T2K or NO$ν$A ($θ_{13}\geq 3^\circ$). Exploitation of matter effects at the CERN to Gran Sasso distance provides sensitivity to the neutrino mass hierarchy in significant areas of the $θ_{13}-δ$ plane.

hep-ph↗

arXiv2006

$ν_μ$ disappearance at the SPL, T2K-I, NO$ν$A and the Neutrino Factory

We study the measurement of the atmospheric neutrino oscillation parameters, $θ_{23}$ and $Δm^2_{23}$, at the $ν_μ$ disappearance channel at three conventional beam facilities, the SPL, T2K-phase I and NO$ν$A. These two parameters have been shown to be of crucial importance in the measurement of two of the unknowns of the PMNS mixing matrix, $θ_{13}$ and the leptonic CP-violating phase $δ$. In our analyis, the effect of the two discrete ambiguities, ${\rm sign}(Δm^2_{23})$ and ${\rm sign}(\tan 2 θ_{23})$, is explicitly taken into account. We analyse also the $ν_μ$ disappearance channel at the Neutrino Factory, and combine it with the ``golden'' $ν_e \to ν_μ$ and ``silver'' $ν_e \to ν_τ$ appearance channels to study its impact on the measurement of $θ_{13}$ and $δ$. Eventually, we present the sensitivity of the four facilities to different observables: $θ_{13}$, $δ$, maximal $θ_{23}$, the sign of the atmospheric mass difference, $s_{atm}$, and the $θ_{23}$-octant, $s_{oct}$.

hep-ph↗

arXiv2005

$ν_μ$ disappearance at the SPL, T2K-I and the Neutrino Factory

We study the $ν_μ$ disappearance channel at T2K-phase I and the SPL and analyse the achievable reduction of present uncertainties in $θ_{23}$ and $Δm^2_{23}$. We analyse the impact of discrete ambiguities in sign($Δm^2{23}$) and sign($2 \tan θ_{23}$). We show how the disappearance channel at the Neutrino Factory is complementary to the ``golden'' and ``silver'' appearance channels and can be used to reduce the eightfold-ambiguity problem in ($θ_{13}-δ$).

hep-ph↗

arXiv2005

Appearance and disappearance signals at a beta-Beam and a Super-Beam facility

In this letter we present the study of the eightfold degeneracy in the $(θ_{13},δ)$ measurement including both appearance and disappearance channels. We analyse, for definiteness, the case of a standard low-$γ$ $β$-Beam and a 4 MWatt SPL Super-Beam facility, both aiming at a UNO-like Mton water Cerenkov detector located at the Frejus laboratory, $L = 130$ km. In the $β$-Beam case, the \nue disappearance channel does not improve the $(θ_{13},δ)$ measurement when a realistic (i.e. $\ge$ 2%) systematic error is included. In the Super-Beam case, the \numu disappearance channel could, instead, be quite useful in reducing the impact of the eightfold degeneracy in the $(θ_{13},δ)$ measurement, especially once the error on the atmospheric mass difference is fully taken into account in the fit.

hep-ph↗

arXiv2004

Study of the eightfold degeneracy with a standard $β$-Beam and a Super-Beam facility

The study of the eightfold degeneracy at a neutrino complex that includes a standard $β$-Beam and a Super-Beam facility is presented for the first time in this paper. The scenario where the neutrinos are sent toward a Megaton water Cerenkov detector located at the Fréjus laboratory (baseline 130 Km) is exploited. The performance in terms of sensitivity for measuring the continuous ($θ_{13}$ and $δ$) and discrete (${sign} [ Δm^2_{23} ]$ and ${sign} [\tan (2θ_{23}) ]$) oscillation parameters for the $β$-Beam and Super-Beam alone, and for their combination has been studied. A brief review of the present uncertainties on the neutrino and antineutrino cross-sections is also reported and their impact on the discovery potential discussed.

hep-ph↗