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Abstract

In the recent years, major milestones in neutrino physics were accomplished
at nuclear reactors: the smallest neutrino mixing angle $\theta_{13}$ was
determined with high precision and the emitted antineutrino spectrum was
measured at unprecedented resolution. However, two anomalies, the first one
related to the absolute flux and the second one to the spectral shape, have yet
to be solved. The flux anomaly is known as the Reactor Antineutrino Anomaly and
could be caused by the existence of a light sterile neutrino eigenstate
participating in the neutrino oscillation phenomenon. Introducing a sterile
state implies the presence of a fourth mass eigenstate, while global fits
favour oscillation parameters around $\sin^{2}(2\theta)=0.09$ and $\Delta
m^{2}=1.8\textrm{eV}^{2}$.
The STEREO experiment was built to finally solve this puzzle. It is one of
the first running experiments built to search for eV sterile neutrinos and
takes data since end of 2016 at ILL Grenoble, France. At a short baseline of 10
metres, it measures the antineutrino flux and spectrum emitted by a compact
research reactor. The segmentation of the detector in six target cells allows
for independent measurements of the neutrino spectrum at multiple baselines. An
active-sterile flavour oscillation could be unambiguously detected, as it
distorts the spectral shape of each cell's measurement differently.
This contribution gives an overview on the STEREO experiment, along with
details on the detector design, detection principle and the current status of
data analysis.