Toward an Energy Model for Electronic Recoils in DarkSide-50

Abstract

Energy depositions in DarkSide-50 (DS-50) are recorded in two anticorrelated com- ponents: prompt scintillation (referred to as S1) and ionization (referred to as S2). The rate at which ionized argon recombines to contribute to S1 is dependent on ion- ization density and drift field, among other factors. We present a common model for electronic recoil energy depositions in DS-50 which seeks to measure two parameters: the light yield in photoelectrons per scintillation photon in S1 (scintillation yield, 1) and light yield per extracted electron in S2 (ionization yield, 2). Scintillation and ionization yield can be measured by varying the recombination rate (r) in the detector. The traditional strategy takes advantage of the drift field dependence of recombination. Alternatively, fluctuations in recombination can be observed in high- energy data where the spread in recombination exceeds the spread in photoelectrons produced. Finally, ionization yield can be measured independently of scintillation yield for events produced by the extraction of single electrons. We examine these methods for measuring these detector-dependent parameters for DS-50 and make recommendations for improving future measurements.