Event categories in the EDELWEISS WIMP search experiment

Four categories of events have been identified in the EDELWEISS-I dark matter experiment using germanium cryogenic detectors measuring simultaneously charge and heat signals. These categories of events are interpreted as electron and nuclear interactions occurring in the volume of the detector, and electron and nuclear interactions occurring close to the surface of the detectors(10-20 mu-m of the surface). We discuss the hypothesis that low energy surface nuclear recoils,which seem to have been unnoticed by previous WIMP searches, may provide an interpretation of the anomalous events recorded by the UKDMC and Saclay NaI experiments. The present analysis points to the necessity of taking into account surface nuclear and electron recoil interactions for a reliable estimate of background rejection factors.Comment: 11 pages, submitted to Phys. Lett.

Background discrimination capabilities of a heat and ionization germanium cryogenic detector

The discrimination capabilities of a 70 g heat and ionization Ge bolometer are studied. This first prototype has been used by the EDELWEISS Dark Matter experiment, installed in the Laboratoire Souterrain de Modane, for direct detection of WIMPs. Gamma and neutron calibrations demonstrate that this type of detector is able to reject more than 99.6% of the background while retaining 95% of the signal, provided that the background events distribution is not biased towards the surface of the Ge crystal. However, the 1.17 kg.day of data taken in a relatively important radioactive environment show an extra population slightly overlapping the signal. This background is likely due to interactions of low energy photons or electrons near the surface of the crystal, and is somewhat reduced by applying a higher charge-collecting inverse bias voltage (-6 V instead of -2 V) to the Ge diode. Despite this contamination, more than 98% of the background can be rejected while retaining 50% of the signal. This yields a conservative upper limit of 0.7 event.day^{-1}.kg^{-1}.keV^{-1}_{recoil} at 90% confidence level in the 15-45 keV recoil energy interval; the present sensitivity appears to be limited by the fast ambient neutrons. Upgrades in progress on the installation are summarized.Comment: Submitted to Astroparticle Physics, 14 page

Technical design and performance of the NEMO3 detector

The development of the NEMO3 detector, which is now running in the Frejus Underground Laboratory (L.S.M. Laboratoire Souterrain de Modane), was begun more than ten years ago. The NEMO3 detector uses a tracking-calorimeter technique in order to investigate double beta decay processes for several isotopes. The technical description of the detector is followed by the presentation of its performance.Comment: Preprint submitted to Nucl. Instrum. Methods A Corresponding author: Corinne Augier ([email protected]

Matière noire non baryonique: détecteurs à scintillation et bolomètres pour la recherche de WIMPs

ManoirParrmi les nombreux candidats à la masse manquante de l'Univers, les WIMPs (Particules Lourdes Interagissant Faiblement) sont des candidats d'autant plus sérieux que leur existence est prévue par les modèles supersymétriques. Dans le cadre de la mise en évidence des WIMPs, nous avons caractérisé deux types de détecteurs qui fonctionnent sur le principe de la détection du recul d'un noyau d'un cristal sous l'impact d'un WIMP, en donnant soit une impulsion de lumière dans un scintillateur soit une impulsion de chaleur dans un bolomètre maintenu à 10 mK dans un cryostat. Nous avons mis au point une méthode de mesure du facteur de quenching d'un scintillateur CsI(Tl) pour des énergies de recul très faibles (de l'ordre de 10 keV). Nous avons également caractérisé un bolomètre en saphir de très gros volume (1110 g) : la résolution obtenue est de 18 keV à mi-hauteur sur la raie du $^{57}$Co à 122 keV avec un seuil de 11 keV pour une température du senseur de 45 mK. Enfin nous proposons une méthode d'analyse des signaux basée sur la transformation en ondelettes, appliquée aussi bien aux données obtenues avec le cristal précédent qu'aux données obtenues par la collaboration EDELWEISS sur le détecteur double composante ionisation-chaleur installé au Laboratoire Souterrain de Modane

Détection directe de la matière noire non baryonique

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Event categories in EDELWEISS : a simple interpretation of the anomalous NaI events

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Dark matter search using a 70g Germanium bolometer in the Frejus underground laboratory

If we analyse the semantic field of the term “anthropology” we find that the idea covers a very wide range. At the same time however, expressed opinion follows three basic ways. First of all through definitions or lists of characteristics. Or else through the choice of methods used to analyse the human fact. Finally there are the moments where a researcher admits that he can define only the contours of a concept whose core he still ignores. We can say that there exists an “anthropology” in an ethnographic sense or a “biological anthropology”. But every thought also has an “anthropological instant”, that is an explicit or implicit representation of humanity which stands out from interpretations and epistemological passages.Pas de résum