Installation, commissioning and performance of the trigger system of the Double Chooz experiment and the analysis of hydrogen capture neutrino events

The Double Chooz experiment is a reactor antineutrino experiment located at Chooz, a small town in the Ardennes region in the north of France close to the Belgium border. The aim of the experiment is to measure the leptonic mixing angle theta13. The antineutrino flux is measured by two identical detectors at different distances from the reactor cores used as neutrino source, in a so called “disappearance” experiment. Double Chooz is a precision experiment because previous experiments indicated a small value of theta13. Therefore, the systematic uncertainties introduced by background events and detector related components have to be as small as possible. The detector and all electronic components have been designed accordingly. The first part of this thesis describes the trigger and timing system of the Double Chooz experiment. This system triggers the data acquisition of the detector. It continuously monitors the signals of the photomultiplier tubes (PMTs) of the detector. These signals are summed for groups of PMTs (group signal) and for all PMTs (sum signal). The group signals are the input signals to the trigger system. They are discriminated by one threshold resulting in a multiplicity condition on the number of active group signal discriminators. The sum signal is discriminated by four thresholds. The default trigger configuration for the Double Chooz experiment is based on a combination on the sum signal discriminators and the multiplicity condition. In addition, the trigger system provides a common clock signal for all data acquisition components and an online event classification to allow an online data reduction. The trigger system was installed and commissioned in 2011. In this thesis the commissioning of the trigger system and its performance is presented. Furthermore the development and tests of possible improvements for the trigger system are presented and discussed. The second part of this thesis introduces a complementary neutrino oscillation analysis with the Double Chooz experiment based on neutron captures by Hydrogen. This analysis allows to use a three times larger fiducial volume compared to the standard analysis based on neutron captures by Gadolinium. Due to the different fiducial volume, systematic uncertainties related to background estimations are partly independent from the standard analysis. Therefore, the analysis provides a partly independent crosscheck of the recent analyses results of the measurement of sin2(2theta13). The presented analysis results in a value of sin2(2theta13) = 0.097 ± 0.034 (stat.) ± 0.034 (syst.) which is in good agreement with all the other measurements of sin2(2theta13) presented in 2012