07-10-2011: Colloquium Thilo Michel

02 - 09 - 2011

Friday 7 October 2011, 11:00h, at Nikhef in H331

Speaker: Thilo Michel (Erlangen)

Title: Searching neutrinoless double beta decay with hybrid pixel detectors

The question whether neutrinos are their own antiparticles or not is still not answered with certainty. A definite observation of neutrinoless double beta decay would answer this question with "Yes, neutrinos are their own antiparticles". Provided that neutrinos and antineutrinos are the same particles, neutrinoless double beta decay – where two neutrons convert at the same time only to two electrons without (anti) neutrino emission – can occur with half-lifes longer than 1025 years only in certain nuclides. Nuclides like 75Ge, 116Cd or 136Xe for example can be used to search for occurrence of the neutrinoless double beta decay in semiconductor, liquid or noble gas detectors. In this talk the relationship between neutrino mass and neutrinoless double beta decay half-life, experimental requirements and some experiments are described. The main part of this talk will focus on the performance and the use of fine pitch pixel detectors with CdTe sensors like the Timepix detector, developed by the Medipix collaboration. The COBRA collaboration, searching for neutrinoless double beta decay in 116Cd, is currently investigating the possibilities for background rejection and the general feasibility of an experiment using CdTe pixel detectors with high granularity. Background measurements in an underground laboratory with the Timepix detector have been performed and motivate that background rejection could be improved with an analysis of the topological information of events given by the pixel detector. Preliminary results of simulation studies concerning detector optimization with a special focus on energy resolution are presented. Experimental results for the identification of events with a signature similar to double beta decay in a measurement with background of single electron tracks will be shown.

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