From the mass of the neutrino to the dating of wine

Abstract

The Neutrino Ettore Majorana Observatory (NEMO) experiment, which is currently running in the Modane underground laboratory is looking for a very rare process of the natural radioactivity, called the neutrinoless double beta decay, in which a nucleus emits two electrons simultaneously. The calculated half-life being so large (∼10 25 years), few counts per year are expected which implies that all the background components have to be reduced by few orders of magnitude. Beside cosmic rays, external γ-rays, neutrons and radon, the detector must be built out of materials containing no measurable radioactive isotopes such as U, Th, Ra and their progenies. Most of the natural radioactive isotopes are γ-emitters. So, in order to be able to select and control the radiopurity of all materials, the Bordeaux group has been involved over several years in the development of low background γ-ray spectrometers, based on the use of HPGe crystals. When applied to the radioactivity measurements of wine, the first measurements have shown that beside the well-known isotope 40 K, the wine contains also weak traces of 137Cs with an activity depending on the vintage. This technique has therefore led to the possibility to date the wine bottles having vintage between 1950 and 1980 or at least to control the year written on the label or on the cork. Furthermore, it has been shown that it is not necessary to open the bottle.