A multi-tiered data structure, analysis toolkit and data processing management system has been constructed using ROOT and CouchDB. This system is well suited for experiments that acquire many ...computer files of raw data over the course of months or years, that are distributed to different computing centers and further reduced in size by several steps of data processing. Data handling for experiments searching for rare events extracted from digitized pulse traces typically fit this description. An implementation of this system has been constructed for the EDELWEISS-III experiment and is described here in some detail. This solution may also serve as a prototype system for the proposed EURECA experiment.
The EDELWEISS Collaboration has performed a direct search for WIMP dark matter using a 320 g heat-and-ionization cryogenic Ge detector operated in a low-background environment in the Laboratoire ...Souterrain de Modane. No nuclear recoils are observed in the fiducial volume in the 30–200 keV energy range during an effective exposure of 4.53 kg
day. Limits for the cross-section for the spin-independent interaction of WIMPs and nucleons are set in the framework of the Minimal Supersymmetric Standard Model (MSSM). The central value of the signal reported by the experiment DAMA is excluded at 90% CL.
The discrimination power of the NTD ionization-heat detectors to distinguish nuclear recoils from electron recoils is affected by events interpreted as surface events. On the basis of the data from ...EDELWEISS I and first data taking of EDELWEISS-2, we present a coherent interpretation and direct evidence that surface events occur and are due to radon daughter deposition on detector surface and close-by surfaces. The estimation of the surface activities of contaminated surface are extracted from the new data taking.
This paper presents our interpretation and understanding of the different backgrounds in the EDELWEISS-I data sets. We analyze in detail the several populations observed, which include gammas, ...alphas, neutrons, thermal sensor events and surface events, and try to combine all data sets to provide a coherent picture of the nature and localization of the background sources. In light of this interpretation, we draw conclusions regarding the background suppression scheme for the EDELWEISS-II phase.
The heat quenching factor
Q
′
(the ratio of the heat signals produced by nuclear and electron recoils of equal energy) of the heat-and-ionization germanium bolometers used by the EDELWEISS ...collaboration has been measured. It is explained how this factor affects the energy scale and the effective quenching factor observed in calibrations with neutron sources. This effective quenching effect is found to be equal to
Q
/
Q
′
, where
Q is the quenching factor of the ionization yield. To measure
Q
′
, a precise EDELWEISS measurement of
Q
/
Q
′
is combined with values of
Q obtained from a review of all available measurements of this quantity in tagged neutron beam experiments. The systematic uncertainties associated with this method to evaluate
Q
′
are discussed in detail. For recoil energies between 20 and 100
keV, the resulting heat quenching factor is
Q
′
=
0.91
±
0.03
±
0.04
, where the two errors are the contributions from the
Q and
Q
/
Q
′
measurements, respectively. The present compilation of
Q values and evaluation of
Q
′
represent one of the most precise determinations of the absolute energy scale for any detector used in direct searches for WIMP dark matter.
This paper reports on the development of a technology involving
-enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for ...neutrinoless double-beta decay. Large mass (
), high optical quality, radiopure
-containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2-0.4 kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the
-value of the double-beta transition of
(3034 keV) is 4-6 keV FWHM. The rejection of the
-induced dominant background above 2.6 MeV is better than
. Less than
activity of
and
in the crystals is ensured by boule recrystallization. The potential of
-enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only
exposure: the two neutrino double-beta decay half-life of
has been measured with the up-to-date highest accuracy as
= 6.90 ± 0.15(stat.) ± 0.37(syst.)
. Both crystallization and detector technologies favor lithium molybdate, which has been selected for the ongoing construction of the CUPID-0/Mo demonstrator, containing several kg of
.
The first data taking of EDELWEISS-II the Dark Matter search with bolometers, measuring simultaneously ionization and heat, indicate the presence of incomplete charge collection events underneath the ...electrodes. These events, interpreted as surface interactions limit strongly the sensibility to WIMPs. In this paper, we are describing the status of the different techniques that are under development in our collaboration to identify and reject this type of events.
A new design of an ionization-heat germanium detector for dark matter search is presented, based on the use of interleaved electrodes for charge collection. This device allows active rejection of ...surface events by performing the appropriate cuts in the charge measurement data. Test experiments were performed with a prototype device, fitted with annular collection electrodes and with a neutron transmutation-doped Ge thermometer. Calibration runs with gamma and neutron sources demonstrate the remarkable possibilities offered by this type of detector in terms of surface event discrimination.
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