Search for eV Sterile Neutrinos - The STEREO Experiment

STEREO is a high precision experiment studying the antineutrinos coming from the core, highly enriched in U-235, of the nuclear reactor of the Institut Laue-Langevin (Grenoble,France). The aim is to investigate two anomalies revealed by the measurements of several reactor neutrino experiments. The first one is linked to the absolute flux coming from a reactor ("Reactor Antineutrino Anomaly [RAA]") and could be explained by the existence of a new oscillation at short baseline to a light sterile neutrino. The second anomaly is related to the shape of the antineutrino energy spectrum where an excess of events compared to the prediction has been measured around 5 MeV ("5 MeV Bump"). Here, preliminary results of the test for a new oscillation using 334(543) days reactor ON(OFF), which constitutes the entire dataset of the STEREO experiment, will be reported. They are compatible with the no-oscillation hypothesis and reject the RAA best-fit at more than 4 sigma. Concerning the analysis of the energy spectrum shape, the results of the analysis of 273(519) days ON(OFF) show a confirmation of the events excess between 5 and 6 MeV.