Münster 2017 – scientific programme

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T: Fachverband Teilchenphysik

T 108: Neutrinophysik 9 (sterile Neutrinos)

T 108.8: Talk

Thursday, March 30, 2017, 18:40–18:55, VSH 118

Pulse Shape Discrimination in the STEREO Neutrino Experiment — •Stefan Schoppmann, Helena Almazán, Christian Buck, Julia Haser, Manfred Lindner, and Christian Roca — Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany

The STEREO experiment is an antineutrino disappearance experiment located at the ILL research reactor in Grenoble, France. Its goal is to test the sterile neutrino hypothesis via oscillations. The detector has a segmented design, to measure the relative effect of neutrino oscillations at six different baselines between 9 and 11 metres. Neutrinos are detected in six Gd-loaded liquid scintillator volumes by the inverse beta decay reaction (IBD). In this reaction, an antineutrino capture by a proton yields a positron, giving a prompt energy deposition and annihilation signal, and a neutron, giving a delayed capture signal after thermalisation.

Due to its proximity to the reactor a significant flux of neutrons reaches the detector. In addition, atmospheric muons produce neutrons via spallation. Neutrons can mimic IBDs as they generate prompt proton recoils followed by their delayed capture. However, the scintillator deexcitation time differs for a proton recoil and a positron or gamma event. Thus, it is possible to distinguish both types of particle signals by analysing the time shape of their scintillation pulses.

This contribution will present in-situ and laboratory measurements of pulse shapes for gamma and neutron events. A strategy for background rejection using scintillation pulse shape will be described and its performance reviewed.