|The Neutrino Ettore Majorana Observatory — NEMO 3/SuperNEMO International Collaboration|
The NEMO 3 experiment investigates neutrinoless double beta decay (DBD). The observation of such a process would provide fundamental informations about neutrinos: their absolute mass scale, their inner nature concerning the matter/antimatter asymmetry (Majorana/Dirac particles) or maybe evidence for supersymmetry!
The NEMO collaboration has been working on this topic since 1989. Two prototype detectors (NEMO 1 and NEMO 2) have been built and used until 1997. From 1994 to 2001, the NEMO collaboration has been involved in the design and construction of a large double beta decay detector: NEMO 3 (see picture).
NEMO 3 is now installed at the Fréjus Underground Laboratory Fréjus Underground Laboratory [ http://www-lsm.in2p3.fr/] (LSM) in Modane (Savoie, France). It is a very low radioactive background detector. Its performances enable the observation of DBD processes with lifetime at the sensitivity of 1024 years. Data collection has officially started on January 14th, 2003.
Our collaboration is currently analysing the experimental data from the NEMO 3 detector, searching for very rare neutrinoless DBD events.
More, the SuperNEMO next generation experiment is currently in R&D phase. We aim to improve the sensitivity to neutrinoless double beta decay by two orders of magnitude (lifetime = 1026 years).
This picture shows a neutrinoless double beta decay candidate event in the NEMO3 detector (top view). From the Geiger signal extracted from the drift cells along the charged particles trajectory (small coloured circles), one can here reconstruct the tracks of two charged particles: the curvatures in the magnetic field are compatible with electrons coming from the source foil (vertex) made of enriched molybdenum. The total energy deposit in the two hit scintillator blocks is 2875 keV which is expected for a neutrinoless double beta decaying 100Mo nucleus ( ) corrected by energy loss in the source foil, the gas of the tracking chamber and convoluted by the calorimeter energy resolution.
The construction of the core mechanical parts of the NEMO 3 detector — the tracking chamber and the calorimeter — has been finished during fall 2001 at the LSM. Here it is shown almost closed, before the assembling of the 20th sector. Later in 2003, the gamma/neutron proof device has been assembled around the detector (a shield made of iron plates, wood panels and tanks full of borated water). Finaly the anti-radon tent (in 2004) encloses the full setup.
Several topics are available from this site (most are under construction):