Production Yield of Muon-Induced Neutrons in Lead Measured at the Modane Underground Laboratory

The work presented in this book is a major step towards understanding and eventually suppressing background in the direct search for dark matter particles scattering off germanium detectors. Although the flux of cosmic muons is reduced by many orders of magnitude in underground laboratories, the remaining energetic muons induce neutrons through various processes, neutrons that can potentially mimic a dark matter signal. This thesis describes the measurement of muon-induced neutrons over more than 3 years in the Modane underground laboratory. The data are complemented by a thorough modeling of the neutron signal using the GEANT4 simulation package, demonstrating the appropriateness of this tool to model these rare processes. As a result, a precise neutron production yield can be presented. Thus, future underground experiments will be able to reliably model the expected rate of muon-induced neutrons, making it possible to develop the necessary shielding concept to suppress this background component.

Introduction.- Edelweiss: Direct Dark Matter Search at LSM.- Review of Muon-Induced Neutron Production at Underground Sites.- Long Term Measurement of Muon-induced Neutrons at LSM.- Assessment of Geant4 to Simulate the Neutron Yield in Lead at LSM.- Conclusion and Outlook.- Appendix.

Dr. Holger Kluck received his Ph.D. at the Karlsruhe Institute of Technology in 2013. Within the EDELWEISS and EURECA collaborations, he investigated the production of muon-induced neutrons both via dedicated measurements at the Modane underground laboratory and in comparison with Monte Carlo models. Since 2014, he is a postdoctoral researcher at the Vienna University of Technology and at the Institute of High Energy Physics of the Austrian Academy of Sciences. Searching for dark matter remains the major topic of his research interests, bringing his experince in background investigations into the CRESST experiment. In addition, he is developping electronics and readout concepts for future dark matter searches such as EURECA.