Investigation of Electron Backscattering on Silicon Drift Detectors for the Sterile Neutrino Search with TRISTAN

TL;DR

This study characterizes electron backscattering in silicon drift detectors used in the TRISTAN experiment, crucial for accurately detecting keV-scale sterile neutrinos and improving the detector response understanding.

Contribution

It provides the first detailed measurement and simulation comparison of electron backscattering effects in silicon drift detectors for neutrino research.

Findings

Measured backscattering probability agrees with Geant4 simulations.

Characterized detector response impacts sterile neutrino search sensitivity.

Improved understanding of detector effects enhances experimental accuracy.

Abstract

Sterile neutrinos are hypothetical particles in the minimal extension of the Standard Model of Particle Physics. They could be viable dark matter candidates if they have a mass in the keV range. The Karlsruhe tritium neutrino (KATRIN) experiment, extended with a silicon drift detector focal plane array (TRISTAN), has the potential to search for keV-scale sterile neutrinos by measuring the kinematics of the tritium $\beta$-decay. The collaboration targets a sensitivity of $10^{-6}$ on the mixing amplitude $\sin^2{\Theta}$. For this challenging target, a precise understanding of the detector response is necessary. In this work, we report on the characterization of electron backscattering from the detector surface, which is one of the main effects that influence the shape of the observed energy spectrum. Measurements were performed with a tandem silicon drift detector system and a custom-designed electron source. The measured detector response and backscattering probability are in good agreement with dedicated backscattering simulations using the Geant4 simulation toolkit.