Calorimeter R&D for the SuperNEMO Double Beta Decay Experiment

SuperNEMO is a next-generation double beta decay experiment based on the successful tracking plus calorimetry design approach of the NEMO3 experiment currently running in the Laboratoire Souterrain de Modane (LSM). SuperNEMO can study a range of isotopes, the baseline isotopes are 82Se and possibly 150Nd. The total isotope mass will be 100-200 kg. A sensitivity to neutrinoless double beta decay half-life greater than 10e26 years can be reached which gives access to Majorana neutrino masses of 50-100 meV. One of the main challenges of the SuperNEMO R&D is the development of the calorimeter with an unprecedented energy resolution of 4% FWHM at 3 MeV (Qbb value of 82Se).Comment: Presented at 13th International Conference on Calorimetry in High Energy Physics (CALOR08), Pavia, Italy, 26-30 May 200

The MGDO software library for data analysis in Ge neutrinoless double-beta decay experiments

The GERDA and Majorana experiments will search for neutrinoless double-beta decay of germanium-76 using isotopically enriched high-purity germanium detectors. Although the experiments differ in conceptual design, they share many aspects in common, and in particular will employ similar data analysis techniques. The collaborations are jointly developing a C++ software library, MGDO, which contains a set of data objects and interfaces to encapsulate, store and manage physical quantities of interest, such as waveforms and high-purity germanium detector geometries. These data objects define a common format for persistent data, whether it is generated by Monte Carlo simulations or an experimental apparatus, to reduce code duplication and to ease the exchange of information between detector systems. MGDO also includes general-purpose analysis tools that can be used for the processing of measured or simulated digital signals. The MGDO design is based on the Object-Oriented programming paradigm and is very flexible, allowing for easy extension and customization of the components. The tools provided by the MGDO libraries are used by both GERDA and Majorana.Comment: 4 pages, 1 figure, proceedings for TAUP201

Elastic Scattering and Direct Detection of Kaluza-Klein Dark Matter

Recently a new dark matter candidate has been proposed as a consequence of universal compact extra dimensions. It was found that to account for cosmological observations, the masses of the first Kaluza-Klein modes (and thus the approximate size of the extra dimension) should be in the range 600-1200 GeV when the lightest Kaluza-Klein particle (LKP) corresponds to the hypercharge boson and in the range 1 - 1.8 TeV when it corresponds to a neutrino. In this article, we compute the elastic scattering cross sections between Kaluza-Klein dark matter and nuclei both when the lightest Kaluza-Klein particle is a KK mode of a weak gauge boson, and when it is a neutrino. We include nuclear form factor effects which are important to take into account due to the large LKP masses favored by estimates of the relic density. We present both differential and integrated rates for present and proposed Germanium, NaI and Xenon detectors. Observable rates at current detectors are typically less than one event per year, but the next generation of detectors can probe a significant fraction of the relevant parameter space.Comment: 23 pages, 11 figures; v2,v3: Ref. added, discussion improved, conclusions unchanged. v4: Introduction was expanded to be more appropriate for non experts. Various clarifications added in the text. Version to be published in New Journal of Physic

A new approach to the front-end readout of cryogenic ionization detectors

We present a novel approach to the readout of ionization detectors. The solution allows to minimize the number of components and the space occupation close to the detector. This way a minimal impact is added on the radioactive background in those experiments where very low signal rates are expected, such as GERDA and MAJORANA. The circuit consists in a JFET transistor and a remote second stage. The DC feedback path is closed using a diode. Two signal cables are only necessary for biasing and readout.Comment: 14 pages, 15 figures and 15 equation

Discovery potential of xenon-based neutrinoless double beta decay experiments in light of small angular scale CMB observations

The South Pole Telescope (SPT) has probed an expanded angular range of the CMB temperature power spectrum. Their recent analysis of the latest cosmological data prefers nonzero neutrino masses, mnu = 0.32+-0.11 eV. This result, if confirmed by the upcoming Planck data, has deep implications on the discovery of the nature of neutrinos. In particular, the values of the effective neutrino mass involved in neutrinoless double beta decay (bb0nu) are severely constrained for both the direct and inverse hierarchy, making a discovery much more likely. In this paper, we focus in xenon-based bb0nu experiments, on the double grounds of their good performance and the suitability of the technology to large-mass scaling. We show that the current generation, with effective masses in the range of 100 kg and conceivable exposures in the range of 500 kg year, could already have a sizable opportunity to observe bb0nu events, and their combined discovery potential is quite large. The next generation, with an exposure in the range of 10 ton year, would have a much more enhanced sensitivity, in particular due to the very low specific background that all the xenon technologies (liquid xenon, high-pressure xenon and xenon dissolved in liquid scintillator) can achieve. In addition, a high-pressure xenon gas TPC also features superb energy resolution. We show that such detector can fully explore the range of allowed effective Majorana masses, thus making a discovery very likely

Pulse shape discrimination studies with a Broad-Energy Germanium detector for signal identification and background suppression in the GERDA double beta decay experiment

First studies of event discrimination with a Broad-Energy Germanium (BEGe) detector are presented. A novel pulse shape method, exploiting the characteristic electrical field distribution inside BEGe detectors, allows to identify efficiently single-site events and to reject multi-site events. The first are typical for neutrinoless double beta decays (0-nu-2-beta) and the latter for backgrounds from gamma-ray interactions. The obtained survival probabilities of backgrounds at energies close to Q(76Ge) = 2039 keV are 0.93% for events from 60Co, 21% from 226Ra and 40% from 228Th. This background suppression is achieved with 89% acceptance of 228Th double escape events, which are dominated by single site interactions. Approximately equal acceptance is expected for 0-nu-2-beta-decay events. Collimated beam and Compton coincidence measurements demonstrate that the discrimination is largely independent of the interaction location inside the crystal and validate the pulse-shape cut in the energy range of Q(76Ge). The application of BEGe detectors in the GERDA and the Majorana double beta decay experiments is under study.Comment: 22 pages, 16 figures, submitted to JINST: JINST_018P_080

Pulse shape discrimination studies with a Broad-Energy Germanium detector for signal identification and background suppression in the GERDA double beta decay experiment

First studies of event discrimination with a Broad-Energy Germanium (BEGe) detector are presented. A novel pulse shape method, exploiting the characteristic electrical field distribution inside BEGe detectors, allows to identify efficiently single-site events and to reject multi-site events. The first are typical for neutrinoless double beta decays (0-nu-2-beta) and the latter for backgrounds from gamma-ray interactions. The obtained survival probabilities of backgrounds at energies close to Q(76Ge) = 2039 keV are 0.93% for events from 60Co, 21% from 226Ra and 40% from 228Th. This background suppression is achieved with 89% acceptance of 228Th double escape events, which are dominated by single site interactions. Approximately equal acceptance is expected for 0-nu-2-beta-decay events. Collimated beam and Compton coincidence measurements demonstrate that the discrimination is largely independent of the interaction location inside the crystal and validate the pulse-shape cut in the energy range of Q(76Ge). The application of BEGe detectors in the GERDA and the Majorana double beta decay experiments is under study.Comment: 22 pages, 16 figures, submitted to JINST: JINST_018P_080

Pulse shape discrimination studies with a Broad-Energy Germanium detector for signal identification and background suppression in the GERDA double beta decay experiment

First studies of event discrimination with a Broad-Energy Germanium (BEGe) detector are presented. A novel pulse shape method, exploiting the characteristic electrical field distribution inside BEGe detectors, allows to identify efficiently single-site events and to reject multi-site events. The first are typical for neutrinoless double beta decays (0-nu-2-beta) and the latter for backgrounds from gamma-ray interactions. The obtained survival probabilities of backgrounds at energies close to Q(76Ge) = 2039 keV are 0.93% for events from 60Co, 21% from 226Ra and 40% from 228Th. This background suppression is achieved with 89% acceptance of 228Th double escape events, which are dominated by single site interactions. Approximately equal acceptance is expected for 0-nu-2-beta-decay events. Collimated beam and Compton coincidence measurements demonstrate that the discrimination is largely independent of the interaction location inside the crystal and validate the pulse-shape cut in the energy range of Q(76Ge). The application of BEGe detectors in the GERDA and the Majorana double beta decay experiments is under study.Comment: 22 pages, 16 figures, submitted to JINST: JINST_018P_080