Gentle Neutron Signals and Noble Background in the XENON100 Dark Matter Search Experiment

This thesis is brought forward to improve the understanding of peculiar aspects concerning signal and background in the XENON100 experiment, which aims at the direct detection of weakly interacting massive particles (WIMPs). These yet undiscovered particles provide a wellmotivated solution to the quest for dark matter in our Universe. Within three years of operation, the XENON100 detector has evolved to become the most sensitive instrument to probe spin-independent WIMP-nucleon cross-sections down to 2.0 x 10^-45- cm^-2- for WIMP masses in the range of 55 GeV/c². We first present an introduction to the detection principle underlying the application of liquid xenon as a target medium for rare event searches. In the following, we summarize our contributions to the suppression of anomalous radiation backgrounds, appearing in the context of reported data analysis for the dark matter searches. We devote the subsequent chapter to the investigation of naturally decaying radon as one of the most dominant sources of internal background. Conclusions drawn are relevant not only for the interpretation of the current background level in XENON100 but also for future detector generations. Finally, we aim at a coherent understanding of nuclear recoil interactions, as mediated by neutrons or potential WIMPs, in the XENON100 detector. Through comparison of neutron calibration data to a dedicated simulation of the entire detector signal response, we derive a measurement of the charge yield and light quenching in liquid xenon, both functions of recoil energy. By achieving absolute and spectral agreement in both accessible signal channels between data and simulation we further provide proof of the correctness and robustness of the interpretation of dark matter results put forward by the XENON100 experiment