AbstractsPhysics

The search for Dark Matter has been one of the hottest areas in astroparticle physics for years, all the more since also the Large Hadron Collider started to test theoretical models for dark matter. WIMPs (Weakly Interacting Massive Particles) are the most prominent candidates for cold dark matter particles, mostly in combination with supersymmetric extensions of the Standard Model of particle physics. In experiments to directly detect WIMPs the main problem is, that the rate of WIMPs scattering on nuclei in the detector is expected to be very small with just a few signals per kg and year. Therefore one of the most important issues in the setup and operation of an experiment is the identification, reduction and control of spurious background signals. It was shown already that the currently achievable sensitivity for an experiment is limited by muons and muon induced particles. For this reason, it is of particular importance to identify muons in the experiment. In underground laboratories the muon flux in experiments is greatly reduced compared to experimental sites at or near the Earth surface. Nevertheless, current low background experiments suffer even from the small muon fluxes in these laboratories of the order of 1/m^2/h or lower. It is therefore mandatory to understand the muon flux in the experiments and be able to actively veto signals which originate from muons. This issue is the motivation for this work, which covers the topic for the CRESST II experiment. An active muon veto system surrounding the dark matter experiment has been installed and operated during several dark matter search runs. The recorded data is analyzed in several ways. First, the performance of the muon veto system is examined with respect to the long-term stability. In this part the focus is on the overall aspects of the data without regarding muon signals. Then, data selection cuts are developed with the aim to define the characteristics of muon signals. The resulting muon safe sample is analyzed and the plausibility of the resulting muon flux at the CRESST experiment is tested against previous selection methods and the expectation from cosmic rays. Finally, coincident signals between the muon signals and events in the detector modules of CRESST are investigated. With the selection of muons determined in this work, a clear and almost background free coincidence signal can be extracted from the data, while for a veto safe selection no coincidences between the muon candidates and the detector modules could be identified above the random coincident level. In this way backtesting of the muon selection is conducted, confirming the data cuts.; Die Suche nach Dunkler Materie ist eines der aktuellsten Gebiete der Astro-Teilchenphysik, was insbesondere seit dem Beginn der Messungen am Large Hadron Collider noch verstärkt der Fall ist, da theoretische Modellannahmen experimentell aus einer rein teilchenphysikalischen Richtung überprüft werden können. Galaktische WIMPs (Weakly…