612 research outputs found
Virtual depth by active background suppression: Revisiting the cosmic muon induced background of GERDA Phase II
In-situ production of long-lived isotopes by cosmic muon interactions may
generate a non-negligible background for deep underground rare event searches.
Previous Monte Carlo studies for the GERDA experiment at LNGS identified the
delayed decays of Ge and its metastable state Ge as dominant
cosmogenic background in the search for neutrinoless double beta decay of
Ge. This might limit the sensitivity of next generation experiments
aiming for increased Ge mass at background-free conditions and thereby
define a minimum depth requirement. A re-evaluation of the Ge
background for the GERDA experiment has been carried out by a set of Monte
Carlo simulations. The obtained Ge production rate is (0.210.01)
nuclei/(kgyr). After application of state-of-the-art active background
suppression techniques and simple delayed coincidence cuts this corresponds to
a background contribution of (2.70.3)
cts/(keVkgyr). The suppression achieved by this strategy equals
an effective muon flux reduction of more than one order of magnitude. This
virtual depth increase opens the way for next generation rare event searches.Comment: 9 pages, 5 figure
LArGe: Background suppression using liquid argon (LAr) scintillation for 0 decay search with enriched germanium (Ge) detectors
Measurements with a bare p-type high purity germanium diode (HPGe) submerged
in a 19 kg liquid argon (LAr) scintillation detector at MPIK Heidelberg are
reported. The liquid argon--germanium system (LArGe) is operated as a 4
anti-Compton spectrometer to suppress backgrounds in the HPGe. This R&D is
carried out in the framework of the GERDA experiment which searches for
0 decays with HPGe detectors enriched in Ge. The goal of
this work is to develop a novel method to discriminate backgrounds in
0 search which would ultimately allow to investigate the
effective neutrino mass free of background events down to the inverse mass
hierarchy scale. Other applications in low-background counting are expected.Comment: 3 pages, 6 figures, conference proceedings of the 10th Topical
Seminar on Innovative Particle and Radiation Detectors (IPRD06) 1 - 5 October
2006 Siena, Ital
PMT Test Facility at MPIK Heidelberg and Double Chooz Super Vertical Slice
Proceedings supplement for conference poster at Neutrino 2010, Athens,
Greece
Topologies of 76 Ge double-beta decay events and calibration procedure biases
The analysis of the time profile of electrical signals produced by energy depositions in germanium detectors allows discrimination of events with different topologies. This is especially relevant for experiments searching for the neutrinoless double beta decay of 76Ge to distinguish the sought-after signal from other background sources. The standard calibration procedures used to tune the selection criteria for double-beta decay events use a 228Th source, because it provides samples of signal-like events. These samples exhibit energy spatial distributions with subtle different topologies compared to neutrinoless double-beta decay events. In this work, we will characterize these topological differences and, with the support of a 56Co source, evaluate biases and precision of calibration techniques which use such event samples. Our results will be particularly relevant for future experiments in which a solid estimation of the efficiency is required
Charge-carrier collective motion in germanium detectors for ββ-decay searches
The time analysis of the signal induced by the drift of charge carriers in high purity germanium detectors provides information on the event topology. Millions of charge carriers are produced in a typical event. Their initial distribution, stochastic diffusion and Coulomb self-repulsion affect the time structure of the signal. We present a comprehensive study of these effects and evaluate their impact on the event discrimination capabilities for the three geometries which will be used in the LEGEND experiment for neutrinoless double-beta decay
KamLAND, terrestrial heat sources and neutrino oscillations
We comment on the first indication of geo-neutrino events from KamLAND and on
the prospects for understanding Earth energetics. Practically all models of
terrestrial heat production are consistent with data within the presently
limited statistics, the fully radiogenic model being closer to the observed
value ( geo-events). In a few years KamLAND should collect
sufficient data for a clear evidence of geo-neutrinos, however discrimination
among models requires a detector with the class and size of KamLAND far away
from nuclear reactors. We also remark that the event ratio from Thorium and
Uranium decay chains is well fixed , a constraint that
can be useful for determining neutrino oscillation parameters. We show that a
full spectral analysis, including this constraint, further reduces the
oscillation parameter space compared to an analysis with an energy threshold
.Comment: 12 pages, RevTeX file, 3 ps figures included in the correct order,
corrected some typos and added references. Accepted for publication on Phys.
Lett.
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