Francesco Capozzi

Self-induced temporal instability from a neutrino antenna

It has been recently shown that the flavor composition of a self-interacting neutrino gas can spontaneously acquire a time-dependent pulsating component during its flavor evolution. In this work, we perform a more detailed study of this effect in a model where neutrinos are assumed to be emitted in a two-dimensional plane from an infinite line that acts as a neutrino antenna. We consider several examples with varying matter and neutrino densities and find that temporal instabilities with various frequencies are excited in a cascade. We compare the numerical calculations of the flavor evolution with the predictions of linearized stability analysis of the equations of motion. The results obtained with these two approaches are in good agreement in the linear regime, while a dramatic speed-up of the flavor conversions occurs in the non-linear regime due to the interactions among the different pulsating modes. We show that large flavor conversions can take place if some of the temporal modes are unstable for long enough, and that this can happen even if the matter and neutrino densities are changing, as long as they vary slowly.

Probing the neutrino mass ordering with KM3NeT-ORCA: Analysis and perspectives

The discrimination of the two possible options for the neutrino mass ordering (normal or inverted) is a major goal for current and future neutrino oscillation experiments. Such goal might be reached by observing high-statistics energy-angle spectra of events induced by atmospheric neutrinos and antineutrinos propagating in the Earth matter. Large volume water-Cherenkov detectors envisaged to this purpose include the so-called KM3NeT-ORCA project (in seawater) and the IceCube-PINGU project (in ice). Building upon a previous work focused on PINGU, we study in detail the effects of various systematic uncertainties on the ORCA sensitivity to the mass ordering, for the reference configuration with 9 m vertical spacing. We point out the need to control spectral shape uncertainties at the percent level, the effects of better priors on the theta-23 mixing parameter, and the benefits of an improved flavor identification in reconstructed ORCA events.

Neutrino oscillations in dark backgrounds

We examine scenarios in which a dark sector (dark matter, dark radiation, or dark energy) couples to the active neutrinos. For light and weakly-coupled exotic sectors we find that scalar, vector, or tensor dark backgrounds may appreciably impact neutrino propagation while remaining practically invisible to all other phenomenological probes. The dark medium may induce small departures from the Standard Model predictions or even offer an alternative explanation of neutrino oscillations. While the propagation of neutrinos is affected in all experiments, atmospheric data currently represent the most promising probe of the new physics scale. We quantify the future sensitivity of the ORCA detector of KM3NeT and the IceCube experiment and find that all exotic effects can be constrained at the level of a few percent of the Earth matter potential, with couplings mediating

Global constraints on neutrino masses and their ordering

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Fast flavor conversions of supernova neutrinos: Classifying instabilities via dispersion relations

-neutrino transitions being most constrained. Long baseline experiments like DUNE may provide additional complementary information on the scale of the dark sector.

Solar neutrinos as a probe of dark matter-neutrino interactions

In this work we focus on the absolute neutrino masses and their ordering, still not known in the standard phenomenology of three massive neutrinos. Interesting constraints on the sum of neutrino masses and on mass ordering (either normal, NO or inverted, IO) can be derived from the combination of neutrino oscillation data, neutrinoless double beta (0νββ) decay experiments, and cosmological data. We derive current bounds on absolute neutrino mass observables by combining in a global data analysis the latest results from oscillation experiments, 0νββ decay limits from the KamLAND-Zen experiment, and constraints from Planck measurements and other cosmological data sets. We found that NO appears to be favored with respect to IO at the level of ∼ 2σ, mainly by neutrino oscillation data (especially atmospheric), corroborated by cosmological data in some cases.