Ionization Quenching by Low Energy Electrons in the Double Chooz Scintillators

The Double Chooz experiment aims to measure theta13 with a sensitivity of sin2 2 theta13 = 0.03. For this purpose, the experiment investigates oscillations of ny e from nuclear reactors with two liquid scintillation detectors. Each detector is divided into four volumes, which are lled with four di erent liquids, three of them being di erent liquid scintillator mixtures. This thesis deals with the light output of the liquid scintillators in response to low-energy electrons (<~ 140 keV). In this energy region the light yield is known to become non-linear due to ionization quenching. A rm knowledge of the light response function is important for an accurate energy reconstruction in the analysis of the Double Chooz data. A Compton coincidence experiment was set up to study the response function of the di erent Double Chooz liquid scintillators and a dedicated software was written for the analysis of the data. Special e orts were taken to control possible systematic errors. The predictions of various quenching models were tested for concordance with the data obtained. All of them were in good agreement with the experiment. The quenching parameters were obtained for each model and scintillator mixtures