Séminaires LAPP

Chasing the light sterile neutrino: status of the reactor antineutrino anomaly and the STEREO experiment

by Alessandro Minotti

Auditorium (LAPP)




In the recent years, major achievements in neutrino physics were accomplished at nuclear reactors: the smallest neutrino mixing angle θ13 was determined with high precision and the emitted antineutrino spectrum was measured at unprecedented resolution.

On the other hand, anomalies have emerged that challenge the well-established three-family description of the neutrino oscillation phenomenon. A discrepancy between estimated and observed neutrino flux, known as reactor antineutrino anomaly (RAA), can be explained by extra sterile neutrino eigenstates, with associated mass states at the eV scale, participating in the oscillation. The emergence of such anomaly has given rise to numerous projects which, with different techniques, seek for oscillation pattern at very short baselines (<10m) by comparing antineutrino spectra at different distances from the neutrino source.

Among these is the STEREO experiment. Conceived in CEA Saclay, where RAA was uncovered, the project involves French and German collaborators and is based at the ILL compact-core research reactor, in Grenoble.

In spite of exclusion plots recently released by a number of experiments, the RAA is still alive and kicking. Uncertainties in the normalization of the neutrino spectra from different fissile isotopes leave room for a possible oscillatory interpretation of the anomaly.

STEREO aims to shed light on these conundrums by looking for unambiguous evidence of active-sterile flavour oscillation, while the measure of the 235U neutrino spectrum will provide valuable information to better understand the mechanism of production of reactor neutrinos.

This talk will present the current panorama of the light sterile neutrino search, with particular emphasis on the outline and current state of the analysis of the STEREO experiment.