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Abstract

The Stereo detector is measuring electron antineutrinos from the research reactor
at the Institut Laue-Langevin (Grenoble, France). Located at ~ 10m from its core
and with a segmented neutrino target, Stereo is searching for light sterile neutrino
oscillations as a possible explanation for the Reactor Antineutrino Anomaly observed
in 2011. An accurate determination of the detection efficiency of the correlated signal
created by the electron antineutrino interaction, v_e + p → e⁺ + n , called inverse beta
decay (IBD) is needed to reach that goal. More concretely, a good understanding of
the detection efficiency for the IBD neutrons is required, in both data and simulation,
since it is one of the dominant systematic uncertainties of the Stereo analysis. An
AmBe neutron source has been deployed throughout the different sub-volumes of the
detector, and has been used to study the properties of the neutron detection with high
accuracy. Among others, the selection cuts, neutron vertex dependencies and neutron
capture models have been specially investigated along this thesis. The AmBe source
has been used to test the modelisation of the gamma cascade emitted after a neutron
capture on gadolinium (nuclei present in the liquid scintillator). This thesis is focused
on studying the most relevant properties in terms of data-to-simulation correction
coefficients, providing thus a crucial input in the oscillation analysis of the Stereo
experiment.