Jean-Eric Campagne

Physics potential of the CERN-MEMPHYS neutrino oscillation project

We consider the physics potential of CERN based neutrino oscillation experiments consisting of a Beta Beam (βB) and a Super Beam (SPL) sending neutrinos to MEMPHYS, a 440 kt water Cerenkov detector at Frejus, at a distance of 130 km from CERN. The θ13 discovery reach and the sensitivity to CP violation are investigated, including a detailed discussion of parameter degeneracies and systematical errors. For SPL sensitivities similar to the ones of the phase II of the T2K experiment (T2HK) are obtained, whereas the βB may reach significantly better sensitivities, depending on the achieved number of total ion decays. The results for the CERN-MEMPHYS experiments are less affected by systematical uncertainties than T2HK. We point out that by a combination of data from βB and SPL a measurement with antineutrinos is not necessary and hence the same physics results can be obtained within about half of the measurement time compared to one single experiment. Furthermore, it is shown how including data from atmospheric neutrinos in the MEMPHYS detector allows to resolve parameter degeneracies and, in particular, provides sensitivity to the neutrino mass hierarchy and the octant of θ23.

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.

Double beta decay of 96Zr

Abstract After 10357 h of running the NEMO-2 tracking detector with an isotopically enriched zirconium source (0.084 mol yr of 96Zr), a ββ2ν decay half-life of T1/2=(2.1+0.8(stat)−0.4(stat)±0.2(syst))·1019 y was measured. Limits with a 90% C.L. on the 96Zr half-lives of 1.0·1021 y for ββ0ν decay to the ground state, 3.9·1020 y to the 2+ excited state and 3.5·1020 y for ββ0νχ0 decay with a Majoron (χ0) were obtained. The data also provide direct limits at the 90% C.L. for the 94Zr half-lives. These limits are 1.1·1017 y for ββ2ν decay to the ground state, 1.9·1019 y for ββ0ν decay to the ground state and 2.3·1018 y for ββ0νχ0 decay to ground state.

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.

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

Abstract The NEMO-2 tracking detector located in the Frejus Underground Laboratory was designed as a prototype for the NEMO-3 detector and to study different modes of double beta decay. Measurements with 100 Mo, 116 Cd, 82 Se and 96 Zr were carried out. Presented here are the experimental half-life limits on double beta decays for new Majoron emission modes and limits on effective neutrino–Majoron coupling constants.

PARISROC, a photomultiplier array integrated read out chip

PARISROC is a complete read out chip, in AMS SiGe 0.35 μm technology, for photomultipliers array. It allows triggerless acquisition for next generation neutrino experiments and it belongs to an R&D program funded by the French national agency for research (ANR) called PMm2: “Innovative electronics for photodetectors array used in High Energy Physics and Astroparticles” (ref.ANR-06-BLAN-0186). The ASIC (Application Specific Integrated Circuit) integrates 16 independent and auto triggered channels with variable gain and provides charge and time measurement by a Wilkinson ADC (Analog to Digital Converter) and a 24-bit Counter. The charge measurement should be performed from 1 up to 300 photo-electrons (p.e.) with a good linearity. The time measurement allowed to a coarse time with a 24-bit counter at 10 MHz and a fine time on a 100ns ramp to achieve a resolution of 1 ns. The ASIC sends out only the relevant data through network cables to the central data storage. This paper describes the front-end electronics ASIC called PARISROC.

Chemical purification of molybdenum samples for the NEMO 3 experiment

Abstract Most currently, viable double beta decay experiments require highly enriched isotopic sources. These sources must be extraordinarily free of radioactive contamination. The double beta decay experiment NEMO 3 will study 100Mo, for which physical and chemical purification techniques have been investigated. The success of the chemical purification process is discussed in the context of ultra-low background, high-purity germanium spectrometer measurements.

Measurement and control of the 214Bi contamination in the ββ NEMO-2 experiment

Abstract In the double beta decay (ββ) experiment NEMO-2, the 214 Bi radioactivity has been measured as background for the ββ processes. The analysis of the 214 Bi contamination has been performed via the signature of 214 Po alpha decay. This method has been applied to data taken with enriched 100 Mo and 116 Cd sources. At the level of NEMO-2s sensitivity, in a 1.0 mole yr study of enriched material, the contamination of the sources can be measured in the range of 2.0 mBq kg −1 . The effects of deposited contamination by 222 Rn are also discussed and estimated at the level of 0.3 mBq per square meter of source foil. Backgrounds for neutrinoless double beta decay (ββ0v) are deduced from these measurements and the consequences for the higher sensitivity ββ experiment NEMO-3 are drawn.

Sky reconstruction for the Tianlai cylinder array

In this paper, we apply our sky map reconstruction method for transit type interferometers to the Tianlai cylinder array. The method is based on the spherical harmonic decomposition, and can be applied to cylindrical array as well as dish arrays and we can compute the instrument response, synthesised beam, transfer function and the noise power spectrum. We consider cylinder arrays with feed spacing larger than half wavelength, and as expected, we find that the arrays with regular spacing have grating lobes which produce spurious images in the reconstructed maps. We show that this problem can be overcome, using arrays with different feed spacing on each cylinder. We present the reconstructed maps, and study the performance in terms of noise power spectrum, transfer function and beams for both regular and irregular feed spacing configurations.

PMm2: R&D on triggerless acquisition for next generation neutrino experiments

The next generation of proton decay and neutrino experiments, the post-SuperKamiokande detectors, such as those that will take place in megaton size water tanks, will require very large surfaces of photo-detection and will produce a large volume of data. Even with large hemispherical photomultiplier tubes (PMTs), the expected number of channels should reach hundreds of thousands. An ANR funded R&D program to implement a solution is presented here. The very large surface of photo-detection is segmented in macro pixels consisting of an array (2 × 2 m2) of 16 hemispherical 12-inch PMTs connected to autonomous underwater front-end electronics working in a triggerless data acquisition mode. The array is powered by a common high voltage and only one data cable allows the connection by network to the surface controller. This architecture allows a considerable reduction of the cost and facilitates the industrialization. This paper presents the complete architecture of the prototype system and tests results with 16 8-inch PMTs, validating the whole electronics, the built-in gain adjustment and the calibration principle.