Hilfe Wegweiser Datenschutzhinweis Impressum Kontakt





Search for the neutrinoless double ß-decay in Gerda Phase I using a Pulse Shape Discrimination technique


Kirsch,  Andrea
Division Prof. Dr. Werner Hofmann, MPI for Nuclear Physics, Max Planck Society;

Externe Ressourcen
Es sind keine Externen Ressourcen verfügbar
Volltexte (frei zugänglich)

(Verlagsversion), 22MB

Ergänzendes Material (frei zugänglich)
Es sind keine frei zugänglichen Ergänzenden Materialien verfügbar

Kirsch, A. (2014). Search for the neutrinoless double ß-decay in Gerda Phase I using a Pulse Shape Discrimination technique. PhD Thesis, Ruprecht-Karls-Universität, Heidelberg.

The Germanium Detector Array (Gerda) experiment, located underground at the INFN Laboratori Nazionali del Gran Sasso (LNGS) in Italy, deploys high-purity germanium detectors to search for the neutrinoless double β-decay (0vββ) of 76Ge. An observation of this lepton number violating process, which is expected by many extensions of the Standard Model, would not only generate a fundamental shift in our understanding of particle physics, but also unambiguously prove the neutrino to have a non-vanishing Majorana mass component. A ifrst phase of data recording lasted from November 2011 to May 2013 - resulting in a total exposure (defined as the product of detector mass and measurement time) of 21.6 kg . yr. Within this thesis a thorough study of this data with special emphasis on the development and scrutiny of an active background suppression technique by means of a signal shape analysis has been performed. Among several investigated multivariate approaches, particularly a selection algorithm based on an artificial neural network is found to yield the best performance; i.a. the background index close to the Q-value of the 0vββ - decay could be suppressed by 45% to 1. 102 cts=(keV. kg.yr), while still retaining a considerably high signal survival fraction of (83 ± 3)% leading to a significant improvement of the experimental sensitivity. The efficiency is derived by a simulation and further validated by substantiated consistency checks availing themselves of measurements taken with different calibration sources and physics data. No signal is observed and a new lower limit of T0v½ (90% C.L.) > 2.2. 1025 yr for the half-life of neutrinoless double β-decay of 76Ge is established.