arXiv subjects

Olga Mena

Publications and source records attributed to Olga Mena.

170 records · Page 10Linked to original sources

arXiv2006

NOvA and T2K: The race for the neutrino mass hierarchy

The determination of the ordering of the neutrino masses (the hierarchy) is probably a crucial prerequisite to understand the origin of lepton masses and mixings and to establish their relationship to the analogous properties in the quark sector. Here, we follow an alternative strategy to the usual neutrino--antineutrino comparison in long baseline neutrino oscillation experiments: we exploit the combination of the neutrino-only data from the NOvA and the T2K experiments by performing these two off-axis experiments at different distances but at the same $ /L$, where $ $ is the mean neutrino energy and $L$ is the baseline. This would require a minor adjustment to the proposed off-axis angle for one or both of the proposed experiments.

hep-ph↗

arXiv2005

Constraining Inverse Curvature Gravity with Supernovae

We show that the current accelerated expansion of the Universe can be explained without resorting to dark energy. Models of generalized modified gravity, with inverse powers of the curvature can have late time accelerating attractors without conflicting with solar system experiments. We have solved the Friedman equations for the full dynamical range of the evolution of the Universe. This allows us to perform a detailed analysis of Supernovae data in the context of such models that results in an excellent fit. Hence, inverse curvature gravity models represent an example of phenomenologically viable models in which the current acceleration of the Universe is driven by curvature instead of dark energy. If we further include constraints on the current expansion rate of the Universe from the Hubble Space Telescope and on the age of the Universe from globular clusters, we obtain that the matter content of the Universe is 0.07 <= omega_m <= 0.21 (95% Confidence). Hence the inverse curvature gravity models considered can not explain the dynamics of the Universe just with a baryonic matter component.

astro-ph↗

arXiv2005

Determining the Neutrino Mass Hierarchy and CP Violation in NOvA with a Second Off-Axis Detector

We consider a Super-NOvA-like experimental configuration based on the use of two detectors in a long-baseline experiment as NOvA. We take the far detector as in the present NOvA proposal and add a second detector at a shorter baseline. The location of the second off-axis detector is chosen such that the ratio L/E is the same for both detectors, being L the baseline and E the neutrino energy. We consider liquid argon and water-Cherenkov techniques for the second off-axis detector and study, for different experimental setups, the detector mass required for the determination of the neutrino mass hierarchy, for different values of theta13. We also study the capabilities of such an experimental setup for determining CP violation in the neutrino sector. Our results show that by adding a second off-axis detector a remarkable enhancement on the capabilities of the current NOvA experiment could be achieved.

hep-ph↗

arXiv2005

Physics Potential of the Fermilab NuMI beamline

We explore the physics potential of the NuMI beamline with a detector located 10 km off-axis at a distant site (810 km). We study the sensitivity to $\sin^2 2 θ_{13}$ and to the CP-violating parameter $\sin δ$ as well as the determination of the neutrino mass hierarchy by exploiting the $ν_μ\to ν_e$ and $\barν_μ\to \barν_e$ appearance channels. The results are illustrated for three different experimental setups to quantify the benefits of increased detector sizes, proton luminosities and $ν_e$ detection efficiencies.

hep-ph↗

arXiv2005

Unveiling Neutrino Mixing and Leptonic CP Violation

We review the present understanding of neutrino masses and mixings, discussing what are the unknowns in the three family oscillation scenario. Despite the anticipated success coming from the planned long baseline neutrino experiments in unraveling the leptonic mixing sector, there are two important unknowns which may remain obscure: the mixing angle $θ_{13}$ and the CP-phase $δ$. The measurement of these two parameters has led us to consider the combination of superbeams and neutrino factories as the key to unveil the neutrino oscillation picture.

hep-ph↗

arXiv2004

Undulant Universe

If the equation of state for "dark energy" varies periodically, the expansion of the Universe may have undergone alternating eras of acceleration and deceleration. We examine a specific form that survives existing observational tests, does not single out the present state of the Universe as exceptional, and suggests a future much like the matter-dominated past: a smooth expansion without a final inflationary epoch.

astro-ph↗

arXiv2004

Untangling CP Violation and the Mass Hierarchy in Long Baseline Experiments

In the overlap region, for the normal and inverted hierarchies, of the neutrino-antineutrino bi-probability space for $ν_μ\to ν_e$ appearance, we derive a simple identity between the solutions in the ($\sin^2 2θ_{13}$, $\sin δ$) plane for the different hierarchies. The parameter $\sin^2 2θ_{13}$ sets the scale of the $ν_μ\to ν_e$ appearance probabilities at the atmospheric $δm^2_{atm} \approx 2.4 \times 10^{-3}$ eV$^2$ whereas $\sin δ$ controls the amount of CP violation in the lepton sector. The identity between the solutions is that the difference in the values of $\sin δ$ for the two hierarchies equals twice the value of $\sqrt{\sin^2 2θ_{13}}$ divided by the {\it critical} value of $\sqrt{\sin^2 2θ_{13}}$. We apply this identity to the two proposed long baseline experiments, T2K and NO$ν$A, and we show how it can be used to provide a simple understanding of when and why fake solutions are excluded when two or more experiments are combined. The identity demonstrates the true complimentarity of T2K and NO$ν$A.

hep-ph↗

arXiv2003

Unified Graphical Summary of Neutrino Mixing Parameters

The neutrino mixing parameters are presented in a number of different ways by the various experiments, e.g. SuperKamiokande, K2K, SNO, KamLAND and Chooz and also by the Particle Data Group. In this paper, we argue that presenting the data in terms of $\sin^2 θ$, where $θ$ is the mixing angle appropriate for a given experiment has a direct physical interpretation. For current atmospheric, solar and reactor neutrino experiments, the $\sin^2 θ$'s are effectively the probability of finding a given flavor in a particular neutrino mass eigenstate. The given flavor and particular mass eigenstate varies from experiment to experiment, however, the use of $\sin^2 θ$ provides a unified picture of all the data. Using this unified picture we present a graphical way to represent these neutrino mixing parameters which includes the uncertainties. All of this is performed in the context of the present experimental status of three neutrino oscillations.

hep-ph↗