Chiara Brofferio: Status of CUORE-0 and CUORE
The experiment uses simple solid-state 130Te detectors, transforming any energy released in a temperature increase. These have good energy resolution and high efficiency, but they force the use of low-temperature technology. 130Te is a good candidate for the decaying isotope.
The experimental facility is located in the LNGS, where it enjoys low fluxes of muons and neutrons. A picture of the laboratory area is shown below.
Cuoricino taught them how to disentangle backgrounds. Apart from the cryostat, which had a contamination in Thorium, residual background is due to degraded particles, that is surface contamination from passive material like copper. Passive methods have been adopted for CUORE for background reduction. A lead shield design and strict material selection, a reduction of the amount of copper facing the crystals. Crystals have also withstood a reduction in contamination at the surface.
Cuore0 is a CUORE tower with the same characteristics, so it is both a prototype and a detector on its own. It is a proof of concept of CUORE in all stages, a test and debug of the CUORE assembly line, and a high-statistics check of the improved uniformity of the bolometric response and of the background reduction. Of course it will extend the physics reach of Cuoricino while CUORE is assembled.
The status of Cuore-0 was summarized next. They have been fighting since May 2012 with the dilution unit and the cryogenic system, which is quite old. Several problems have shown up, requiring several stops and delays. In August 2012 they were able to perform a short calibration. They are still waiting for real data. They expect to be able to glue the first two towers of cuore by May.
The speaker showed sensitivity curves in the half-life of the 0-neutrino decay mode. They are considering two hypothesis for the background surface contamination. In five years of running, CUORE should be capable of reaching out to half-lifes of 10^26 years. Cuore-0 on the other hand can have some input on disproving the claim, but only at 1-sigma level.
Other physics measurements are possible with CUORE. Reduction of low-energy background levels allow dark-matter searches a’la Dama, search for axions, supernova watches, and study of rare nuclear transitions. One needs a new trigger algorithm that can lower the energy threshold to a few keV.