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Abstract

Liquid rare gases have been gaining popularity as detector media in rare event searches, especially dark matter experiments, and one factor driving their adoption is the possibility to recognise different types of ionizing radiation by the pulse shapes they evoke. This work on pulse shape discrimination in a liquid argon scintillation detector was done in the framework of the GERDA experiment, where liquid argon scintillation signals may be used for background suppression purposes. Liquid argon scintillation signals were measured using the LArGe@MPI-K setup and in addition, signals were simulated by Monte Carlo methods. Two discrimination algorithms, the "fast to total" and the Gatti filter, are tested on both experimental and simulated pulse shapes with respect to the discrimination power they afford. The discrimination power between photon and neutron induced events achieved with the "fast to total" filter on simulated pulse shapes with 70 detected photons is 2.5 x10⁶ at over 99% acceptance, while on the measured pulse shapes at a threshold of 72 photo electrons a discrimination power of ≤ 4.3 x 10^-4