eprintid: 17149
rev_number: 10
eprint_status: archive
userid: 1277
dir: disk0/00/01/71/49
datestamp: 2014-07-22 06:07:19
lastmod: 2014-08-12 09:09:41
status_changed: 2014-07-22 06:07:19
type: doctoralThesis
metadata_visibility: show
creators_name: Kirsch, Andrea
title: Search for the neutrinoless double beta-decay
in Gerda Phase I
using a Pulse Shape Discrimination technique
subjects: ddc-530
divisions: i-130001
adv_faculty: af-13
abstract: 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 beta-decay (0vbb) 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 first 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 0vbb-
decay could be suppressed by 45% to 1*10^(-2) 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 T(90%C.L.)>2.2*10^25 yr for the half-life of neutrinoless double beta-decay of 76Ge is
established.
date: 2014
id_scheme: DOI
id_number: 10.11588/heidok.00017149
ppn_swb: 1658797310
own_urn: urn:nbn:de:bsz:16-heidok-171493
date_accepted: 2014-07-09
advisor: HASH(0x55de57c7afc0)
language: eng
bibsort: KIRSCHANDRSEARCHFORT2014
full_text_status: public
citation:   Kirsch, Andrea  (2014) Search for the neutrinoless double beta-decay in Gerda Phase I using a Pulse Shape Discrimination technique.  [Dissertation]     
document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/17149/1/Doktorarbeit.pdf