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Abstract

The reactor neutrino experiment Double Chooz searches for the last unknown neutrino mixing angle θ₁₃ which is connected to fundamental open questions in particle physics. A two-detector concept is employed to analyze disappearance of electron antineutrinos at a baseline of one kilometer. A gadoliniumloaded organic liquid scintillator is used as a neutrino target. The gadolinium-free Gamma Catcher scintillator surrounds the neutrino target to improve the detector efficiency and its error. The light yields of Target and Gamma Catcher have been optimized and matched with laboratory measurements, an energy transfer model and Monte Carlo simulations. An analysis of detector data demonstrates that the light yield matching was successful at the one percent level. Optical stability for the first 3.5 months of far detector data taking is shown. The energy reconstruction was improved by laboratory measurements and Monte Carlo tuning of the ionization quenching effect for electrons and alpha particles. In addition, simulations of the position dependent detector light collection efficiency led to an inhomogeneity correction method. The detector response timing was studied for alphas and electrons and the scintillator photon emission times were actively tuned to enhance pulse shape discrimination capabilities.