Challenges in Double Beta Decay

After nearly 80 years since the first guess on its existence, neutrino still escapes our insight: the mass and the true nature (Majorana or Dirac) of this particle is still unknown. In the past ten years, neutrino oscillation experiments have finally provided the incontrovertible evidence that neutrinos mix and have finite masses. These results represent the strongest demonstration that the Standard Model of electroweak interactions is incomplete and that new Physics beyond it must exist. None of these experimental efforts could however shade light on some of the basic features of neutrinos. Indeed, absolute scale and ordering of the masses of the three generations as well as charge conjugation and lepton number conservation properties are still unknown. In this scenario, a unique role is played by the Neutrinoless Double Beta Decay searches: these experiments can probe lepton number conservation, investigate the Dirac/Majorana nature of the neutrinos and their absolute mass scale (hierarchy problem) with unprecedented sensitivity. Today Neutrinoless Double Beta Decay faces a new era where large scale experiments with a sensitivity approaching the so-called degenerate-hierarchy region are nearly ready to start and where the challenge for the next future is the construction of detectors characterized by a tonne-scale size and an incredibly low background, to fully probe the inverted-hierarchy region. A number of new proposed projects took up this challenge. These are based either on large expansions of the present experiments or on new ideas to improve the technical performance and/or reduce the background contributions. n this paper, a review of the most relevant ongoing experiments is given. The most relevant parameters contributing to the experimental sensitivity are discussed and a critical comparison of the future projects is proposed.Comment: 70 pages, 16 figures, 6 tables. arXiv admin note: text overlap with arXiv:1109.5515, arXiv:hep-ex/0501010, arXiv:0910.2994 by other author

Expectations for a new calorimetric neutrino mass experiment

A large calorimetric neutrino mass experiment using thermal detectors is expected to play a crucial role in the challenge for directly assessing the neutrino mass. We discuss and compare here two approaches to the estimation of the experimental sensitivity of such an experiment. The first method uses an analytic formulation and allows to readily obtain a sensible estimate over a wide range of experimental configurations. The second method is based on a frequentist Montecarlo technique and is more precise and reliable. The Montecarlo approach is then exploited to study the main sources of systematic uncertainties peculiar to calorimetric experiments. Finally, the tools are applied to investigate the optimal experimental configuration for a calorimetric experiment with Rhenium based thermal detectors.Comment: 25 pagers, 16 figure

Generation of Noise Time Series with arbitrary Power Spectrum

Noise simulation is a very powerful tool in signal analysis helping to foresee the system performance in real experimental situations. Time series generation is however a hard challenge when a robust model of the noise sources is missing. We present here a simple computational technique which allows the generation of noise samples of fixed length, given a desired power spectrum. A few applications of the method are also discussed.Comment: 4 pages, 7 figure

3d N = 2 mirror symmetry, pq-webs and monopole superpotentials

D3 branes stretching between webs of (p,q) 5branes provide an interesting class of 3d N=2 theories. For generic pq-webs however the low energy field theory is not known. We use 3d mirror symmetry and Type IIB S-duality to construct Abelian gauge theories corresponding to D3 branes ending on both sides of a pq-web made of many coincident NS5's intersecting one D5. These theories contain chiral monopole operators in the superpotential and enjoy a non trivial pattern of global symmetry enhancements. In the special case of the pq-web with one D5 and one NS5, the 3d low energy SCFT admits three dual formulations. This triality can be applied locally inside bigger quiver gauge theories. We prove our statements using partial mirror symmetry `a la Kapustin-Strassler, showing the equality of the S^3_b partition functions and studying the quantum chiral rings

A bolometric measurement of the antineutrino mass

High statistics calorimetric measurements of the beta spectrum of 187Re are being performed with arrays of silver perrhenate crystals operated at low temperature. After a modification of the experimental set-up, which allowed to substantially reduce the background of spurious counts and therefore to increase the sensitivity on the electron antineutrino mass, a new measurement with 10 silver perrhenate microbolometers is running since July 2002. The crystals have masses between 250 and 350 micrograms and their average FWHM energy resolution, constantly monitored by means of fluorescence X-rays, is of 28.3 eV at the beta end-point. The Kurie plot collected during 4485 hours x mg effective running time has an end-point energy of 2466.1 +/- 0.8{stat} +/- 1.5 {syst} eV, while the half lifetime of the decay is found to be 43.2 +/- 0.2{stat} +/- 0.1{syst} Gy. These values are the most precise obtained so far for 187Re. From the fit of the Kurie plot we can deduce a value for the squared electron antineutrino mass m(nu)^2 of 147 +/- 237{stat} +/- 90{syst} eV^2. The corresponding 90% C.L. upper limit for m(nu) is 21.7 eV.Comment: 3 pages, 3 figures. Submitted to Phys. Rev. Let

The 4 K outer cryostat for the CUORE experiment: construction and quality control

The external shell of the CUORE cryostat is a large cryogen-free system designed to host the dilution refrigerator and the bolometers of the CUORE experiment in a low radioactivity environment. The three vessels that form the outer shell were produced and delivered to the Gran Sasso underground Laboratories in July 2012. In this paper, we describe the production techniques and the validation tests done at the production site in 2012.Comment: 11 pages, 13 figures; to appear in NIM