E. Longo

CUORE EXPERIMENT: THE SEARCH FOR NEUTRINOLESS DOUBLE BETA DECAY

The main purpose of the Cryogenic Underground Observatory for Rare Events (CUORE) experiment is the search for the Neutrinoless Double Beta Decay (0νDBD) of 130Te reaching a sensitivity on Majorana mass better than 50 meV. Cuoricino represents not only the first stage of CUORE, but also the most massive 0νDBD experiment presently running. Present results and future planning of these experiments will be described in the paper.

An active-shield method for the reduction of surface contamination in CUORE

The main goal of the CUORE experiment is to search for the neutrinoless double beta decay of 130Te. As it is a rare nuclear decay, the sensitivity of the experiment strongly depends on the background level in the transition energy region. In this paper we describe the R&D work performed to develop an active method for the reduction of radioactive background in CUORE. The idea is to reject events originated by surface contamination in large mass bolometric detectors by using bolometers sensitive to surface events. Results obtained with the first prototypes and tests made with large mass surface sensitive bolometers will be reported.

New CUORICINO results on the way to CUORE

CUORE is a 0.75 ton experiment to search for neutrinoless double beta decay of Te130 using 988 TeO2 bolometers. It aims at reaching a sensitivity on the effective neutrino mass of the order of few tens of meV. CUORICINO, a single CUORE tower running since 2003, plays an important role as a stand alone experiment and for developing the future CUORE setup. Present results already achieved and studies that are underway are here presented and discussed.

CUORE: An experiment to investigate for neutrinoless double beta decay by cooling 750 kg of TeO2 crystals at 10mK

CUORE (Cryogenic Underground Observatory for Rare Events) is an experiment proposed to infer the effective Majorana mass of the electron neutrino from measurements on neutrinoless double beta decay (0νDBD). The goal of CUORE is to achieve a background rate in the range 0.001 to 0.01 counts/keV/kg/y at the 0νDBD transition energy of 130Te (2528 keV). The proposed experiment, to be mounted in the underground Gran Sasso INFN National Laboratory, Italy, is realized by cooling about 1000 TeO2 bolometers, of 750 g each, at a temperature of 10mK. We will describe the experiment, to be cooled by an extremely powerful dilution refrigerator, operating with no liquid helium, and the main experimental features designed to assure the predicted sensitivity. We present moreover the last results of a small scale (40.7 kg) 0νDBD experiment carried on in the Gran Sasso Laboratory (CUORICINO).

Results from cuoricino experiment and prospects for cuore

M. Pedretti, R. Ardito, C. Arnaboldi, D. R. Artusa, F. T. Avignone III, M. Balata, I. Bandac, M. Barucci, J.W. Beeman, F. Bellini, C. Brofferio, C. Bucci, S. Capelli, F. Capozzi, L. Carbone, S. Cebrian, M. Clemenza, C. Cosmelli, O. Cremonesi, R. J. Creswick, I. Dafinei, A. de Waard, M. Diemoz, M. Dolinski, H. A. Farach, F. Ferroni, E. Fiorini, C. Gargiulo, E. Guardincerri, A. Giuliani, P. Gorla, T.D. Gutierrez, E. E. Haller, I. G. Irastorza, E. Longo, G. Maier, R. Maruyama, S. Morganti, S. Nisi, C. Nones, E. B. Norman, A. Nucciotti, E. Olivieri, P. Ottonello, M. Pallavicini, V. Palmieri, M. Pavan, G. Pessina, S. Pirro, E. Previtali, B. Quiter, L. Risegari, C. Rosenfeld, S. Sangiorgio, M. Sisti, A. R. Smith, L. Torres, G. Ventura, N. Xu, and L. Zanotti

Passive shielding in CUORE

The nature of neutrino mass is one of the friontier problems of fundamental physics. Neutrinoless Double Beta Decay (0νDBD) is a powerful tool to investigate the mass hierarchy and possible extensions of the Standard Model. CUORE is a 1‐Ton next generation experiment, made of 1000 Te bolometers, aiming at reaching a background of 0.01 (possibly 0.001) counts keV−1kg−1y−1 and therefore a mass sensitivity of few tens of meV The background contribution due to environmental neutrons, muon‐induced neutrons in the shieldings and external gamma is discussed.

New CUORICINO results and status of CUORE

CUORICINO is an array of 62 TeO2 bolometers with a total mass of 40.7 kg (11.2 kg of 130Te), operated at about 10 mK to search for ββ(0ν) of 130Te. The detectors are organized as a 14-story tower and intended as a slightly modified version of one of the 19 towers of the CUORE project, a proposed tightly packed array of 988 TeO2 bolometers (741 kg of total mass of TeO2) for ultralow-background searches on neutrinoless double-beta decay, cold dark matter, solar axions, and rare nuclear decays. Started in April 2003 at the Laboratori Nazionali del Gran Sasso (LNGS), CUORICINO data taking was stopped in November 2003 to repair the readout wiring system of the 62 bolometers. Restarted in spring 2004, CUORICINO is presently the most sensitive running experiment on neutrinoless double-beta decay. No evidence for ββ(0ν) decay has been found so far and a new lower limit, T12/0ν ≥ 1.8 × 1024 yr (90% C.L.), is set, corresponding to 〈mν〉 ≤ 0.2–1.1 eV, depending on the theoretical nuclear matrix elements used in the analysis. Detector performance, operational procedures, and background analysis results are reviewed. The expected performance and sensitivity of CUORE is also discussed.