DarkSide-50 is a direct detection experiment searching for WIMP dark matter operated at Laboratori Nazionali del Gran Sasso, consisting of a dual-phase argon time projection chamber nested within an active neutron veto. The core detector is filled with a target of argon extracted from underground sources that is depleted in radioactive Argon-39.

This thesis details the blind analysis of 532.4 live-days of data acquired between Aug 2015 and Oct 2017. Particular attention will be paid to the analysis of the electron recoil background, which includes: estimating the rates of radioisotope decay that are responsible; modeling the scintillation response of electron recoil events in liquid argon; and developing a cut utilizing pulse-shape discrimination to control the electron recoil background.

We observe a background- and signal- free result, and report a 90% C.L. upper limit on the spin-independent WIMP-nucleon scattering cross-section of 1.1e-44 cm2 (3.8e-44 cm2, 3.4e-43 cm 2) for a WIMP mass of 100 GeV/c2 (1 TeV/c2}, 10 TeV/c2).