412 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
Overview of the European Underground Facilities
Deep underground laboratories are the only places where the extremely low
background radiation level required for most experiments looking for rare
events in physics and astroparticle physics can be achieved. Underground sites
are also the most suitable location for very low background gamma-ray
spectrometers, able to assay trace radioactive contaminants. Many operational
infrastructures are already available worldwide for science, differing for
depth, dimension and rock characteristics. Other underground sites are emerging
as potential new laboratories. In this paper the European underground sites are
reviewed, giving a particular emphasis on their relative strength and
complementarity. A coordination and integration effort among the European Union
underground infrastructures was initiated by the EU-funded ILIAS project and
proved to be very effective.Comment: Prepared for the Proceedings of the Topical Workshop in Low
Radioactivity Techniques (Sudbury, Canada), August 28-29, 2010m (LRT2010). To
be published on AIP conference proceeding
Neutron- and muon-induced background in underground physics experiments
Background induced by neutrons in deep underground laboratories is a critical
issue for all experiments looking for rare events, such as dark matter
interactions or neutrinoless 2-beta decay. Neutrons can be produced either by
natural radioactivity, via spontaneous fission or (alpha,n) reactions, or by
interactions initiated by high-energy cosmic rays. In all underground
experiments, Monte Carlo simulations of neutron background play a crucial role
for the evaluation of the total background rate and for the optimization of
rejection strategies. The Monte Carlo methods that are commonly employed to
evaluate neutron-induced background and to optimize the experimental setup, are
reviewed and discussed. Focus is given to the issue of reliability of Monte
Carlo background estimates.Comment: 10 pages, 8 figures. Presented in the IV ILIAS Annual Meeting.
Accepted for publication on EPJ
Complete results for five years of GNO solar neutrino observations
We report the complete GNO solar neutrino results for the measuring periods
GNO III, GNO II, and GNO I. The result for GNO III (last 15 solar runs) is
[54.3 + 9.9 - 9.3 (stat.)+- 2.3 (syst.)] SNU (1 sigma) or [54.3 + 10.2 - 9.6
(incl. syst.)] SNU (1 sigma) with errors combined. The GNO experiment is now
terminated after altogether 58 solar exposure runs that were performed between
May 20, 1998 and April 9, 2003. The combined result for GNO (I+II+III) is [62.9
+ 5.5 - 5.3 (stat.) +- 2.5 (syst.)] SNU (1 sigma) or [62.9 + 6.0 - 5.9] SNU (1
sigma) with errors combined in quadrature. Overall, gallium based solar
observations at LNGS (first in GALLEX, later in GNO) lasted from May 14, 1991
through April 9, 2003. The joint result from 123 runs in GNO and GALLEX is
[69.3 +- 5.5 (incl. syst.)] SNU (1 sigma). The distribution of the individual
run results is consistent with the hypothesis of a neutrino flux that is
constant in time. Implications from the data in particle- and astrophysics are
reiterated.Comment: 22 pages incl. 9 Figures and 8 Tables. to appear in: Physics Letters
B (accepted April 13, 2005) PACS: 26.65.+t ; 14.60.P
Monte Carlo evaluation of the external gamma, neutron and muon induced background sources in the CUORE experiment
CUORE is a 1 ton scale cryogenic experiment aiming at the measurement of the
Majorana mass of the electron neutrino. The detector is an array of 988 TeO2
bolometers used for a calorimetric detection of the two electrons emitted in
the BB0n of 130Te. The sensitivity of the experiment to the lowest Majorana
mass is determined by the rate of background events that can mimic a BB0n. In
this paper we investigate the contribution of external sources i.e.
environmental gammas, neutrons and cosmic ray muons to the CUORE background and
show that the shielding setup designed for CUORE guarantees a reduction of this
external background down to a level <1.0E-02 c/keV/kg/y at the Q-value, as
required by the physical goal of the experiment.Comment: 14 pages, 7 figure
Signal modeling of high-purity Ge detectors with a small read-out electrode and application to neutrinoless double beta decay search in Ge-76
The GERDA experiment searches for the neutrinoless double beta decay of Ge-76
using high-purity germanium detectors enriched in Ge-76. The analysis of the
signal time structure provides a powerful tool to identify neutrinoless double
beta decay events and to discriminate them from gamma-ray induced backgrounds.
Enhanced pulse shape discrimination capabilities of "Broad Energy Germanium"
detectors with a small read-out electrode have been recently reported. This
paper describes the full simulation of the response of such a detector,
including the Monte Carlo modeling of radiation interaction and subsequent
signal shape calculation. A pulse shape discrimination method based on the
ratio between the maximum current signal amplitude and the event energy applied
to the simulated data shows quantitative agreement with the experimental data
acquired with calibration sources. The simulation has been used to study the
survival probabilities of the decays which occur inside the detector volume and
are difficult to assess experimentally. Such internal decay events are produced
by the cosmogenic radio-isotopes Ge-68 and Co-60 and the neutrinoless double
beta decay of Ge-76. Fixing the experimental acceptance of the double escape
peak of the 2.614 MeV photon to 90%, the estimated survival probabilities at
Qbb = 2.039 MeV are (86+-3)% for Ge-76 neutrinoless double beta decays,
(4.5+-0.3)% for the Ge-68 daughter Ga-68, and (0.9+0.4-0.2)% for Co-60 decays.Comment: 27 pages, 17 figures. v2: fixed typos and references. Submitted to
JINS
The NUMEN Project: Toward new experiments with high-intensity beams
The search for neutrinoless double-beta (0νββ) decay is currently a key topic in physics, due to its possible wide implications for nuclear physics, particle physics, and cosmology. The NUMEN project aims to provide experimental information on the nuclear matrix elements (NMEs) that are involved in the expression of 0νββ decay half-life by measuring the cross section of nuclear double-charge exchange (DCE) reactions. NUMEN has already demonstrated the feasibility of measuring these tiny cross sections for some nuclei of interest for the 0νββ using the superconducting cyclotron (CS) and the MAGNEX spectrometer at the Laboratori Nazionali del Sud (LNS.) Catania, Italy. However, since the DCE cross sections are very small and need to be measured with high sensitivity, the systematic exploration of all nuclei of interest requires major upgrade of the facility. R&D for technological tools has been completed. The realization of new radiation-tolerant detectors capable of sustaining high rates while preserving the requested resolution and sensitivity is underway, as well as the upgrade of the CS to deliver beams of higher intensity. Strategies to carry out DCE cross-section measurements with high-intensity beams were developed in order to achieve the challenging sensitivity requested to provide experimental constraints to 0νββ NMEs
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Providing environmental representation and environmental effects in the DMSO HLA: Experiences from one protofederation
Argonne National Laboratory participated in the HLA prototyping effort as a member of the Joint Training Federation prototype (JTFp) team. Within the JTFp, Argonne provided the common environmental representation and functionality for the federation utilizing the Dynamic Environmental Effects Model (DEEM). In addition to acting as a source of environmental representation and functionality to the JTFp, DEEM was also used as a Scenario Monitor for the overall simulation to provide a commander`s eyeview of the simulated engagement. In this paper, the authors discuss the procedures used to arrive at a common environmental representation for the federation and to summarize the environmental functionality that was provided. In addition, they present results detailing any performance implications related to providing environmental representation and functionality in future HLA federations
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