J.L. Guyonnet

First results of the search for neutrinoless double-beta decay with the NEMO 3 detector.

The NEMO 3 detector, which has been operating in the Frejus underground laboratory since February 2003, is devoted to the search for neutrinoless double beta decay (bb0nu). Half-lives of the two neutrino double beta decays (bb2nu) have been measured for 100Mo and 82Se. After 389 effective days of data collection from February 2003 until September 2004 (Phase I), no evidence for neutrinoless double beta decay was found from ~7kg of 100Mo and ~1 kg of 82Se. The corresponding lower limits for the half-lives are 4.6 x 10^23 years for 100Mo and 1.0 x10^23 years for 82Se (90% C.L.). Depending on the nuclear matrix elements calculation, limits for the effective Majorana neutrino mass are<0.7-2.8 eV for 100Mo and<1.7-4.9 eV for 82Se

Technical design and performance of the NEMO 3 detector

Abstract The development of the Neutrino Ettore Majorana Observatory (NEMO ∼ 3 ) 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 NEMO 3 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.

Double-β decay of 82Se

Abstract The NEMO-2 tracking detector located in the Frejus Underground Laboratory was designed as a prototype of the NEMO-3 detector to study neutrinoless (Oν) and two neutrino (2ν) double-beta decay (ββ) physics. After 10357 h of running with an isotopically enriched selenium source (2.17 mol yr of 82Se) a ββ2ν decay half-life of T 1 2 = (0.83 ± 0.10( stat ) ± 0.07 ( syst )) × 10 20 yr was measured. Limits with a 90% C.L. on the 82Se half-lives of 9.5 × 1021 yr for ββ0ν decay to the ground state, 2.8 × 1021 yr to the (2+) excited state and 2.4 × 1021 yr for ββ0νχ0 decay with a Majoron (χ0) were also obtained.

Limits on different Majoron decay modes of Mo-100 and Se-82 for neutrinoless double beta decays in the NEMO-3 experiment

Abstract The NEMO-3 tracking detector is located in the Frejus Underground Laboratory. It was designed to study double beta decay in a number of different isotopes. Presented here are the experimental half-life limits on the double beta decay process for the isotopes 100Mo and 82Se for different majoron emission modes and limits on the effective neutrino–majoron coupling constants. In particular, new limits on “ordinary” majoron (spectral index 1) decay of 100Mo ( T 1 / 2 > 2.7 × 10 22 yr ) and 82Se ( T 1 / 2 > 1.5 × 10 22 yr ) have been obtained. Corresponding bounds on the majoron–neutrino coupling constant are 〈 g e e 〉 ( 0.4 – 1.8 ) × 10 −4 and ( 0.66 – 1.9 ) × 10 −4 .

Performance of a prototype tracking detector for double beta decay measurements

Abstract To investigate double beta decay processes, the NEMO collaboration began a long-range research and development program in 1988. The NEMO 2 detector, which is now running in the Frejus underground laboratory (L.S.M. Laboratoire Souterrain de Modane), is the second prototype. It consists of a 1 m2 source foil sandwiched between Geiger cell drift chambers for electron tracking and two plastic scintillator walls for energy and time-of-flight measurements. The technical description of the detector is followed by the study of the various sources of background.

The OPERA experiment Target Tracker

The main task of the Target Tracker detector of the long baseline neutrino oscillation OPERA experiment is to locate in which of the target elementary constituents, the lead/emulsion bricks, the neutrino interactions have occurred and also to give calorimetric information about each event. The technology used consists in walls of two planes of plastic scintillator strips, one per transverse direction. Wavelength shifting fibres collect the light signal emitted by the scintillator strips and guide it to both ends where it is read by multi-anode photomultiplier tubes. All the elements used in the construction of this detector and its main characteristics are described.

Beam tests of a Fast-RICH prototype with VLSI readout electronics

Abstract In this report we discuss the Fast Ring Imaging Cherenkov technique that we have developed for application to proximity-focused LiF (or CaF2) solid radiator and multiwire chamber photon detector with cathode-pad readout using TEA in CH4 as photosensor. We describe the full-scale Prototype of 12 000 pads (5.334 × 6.604 mm2) we have built, and briefly the dedicated VLSI readout electronics we have developed. We report in detail the investigations we have performed in a hadron test beam at the CERN PS, and compare the results obtained to the expected performances. The maximum momentum for π/K separation at 3σ achieved in these tests is 2.86 GeV/c for LiF (2.39 GeV/c for CaF2). The experimentally achieved Cherenkov merit factors, after correction for azimuthal angle acceptance, are N0 = 65.5 cm−1 (57.7 cm−1), to be compared with 53.8 cm−1 (50.2 cm−1) from Monte Carlo calculations. Operation of the detector over several months has proven the technique reliable and robust, and suitable for application in high-luminosity hadron colliders like LHC, as well as e+e− B-Factories like KEK (Japan), SLAC (USA), and Cornell (USA).

Study of 2β-decay of 100Mo and 82Se using the NEMO3 detector

AbstractAfter analysis of 5797 h of data from the detector NEMO3, new limits on neutrinoless double beta decay of 100Mo (T1/2>3.1×1023y, 90% CL) and 82Se (T1/2>1.4×1023y, 90% CL) have been obtained. The corresponding limits on the effective majorana neutrino mass are: 〈mv〉<(0.8–1.2) eV and 〈mv〉<(1.5–3.1) eV, respectively. Also the limits on double-beta decay with Majoron emission are: T1/2>1.4×1022y (90% CL) for 100Mo and T1/2>1.2×1022y (90% CL) for 82Se. Corresponding bounds on the Majoron-neutrino coupling constant are 〈 gee〉<(0.5–0.9)×10−4 and <(0.7−1.6)×10−4. Two-neutrino 2β-decay half-lives have been measured with a high accuracy,

Limits on different Majoron decay modes of 100 Mo, 116 Cd, 82 Se and 96 Zr for neutrinoless double beta decays in the NEMO-2 experiment

T_{1/2}^{100_{Mo} } = [7.68 \pm 0.02(stat) \pm 0.54(syst)] \times 10^{18} y