21 research outputs found
From Cuoricino to CUORE: investigating the inverted hierarchy region of neutrino mass
Cuoricino is a Double Beta Decay experiment operating deep underground, in the Laboratori Nazionali del Gran Sasso, Italy; at a depth of about 3500 m.w.e. The search for the 0νββ of 130Te is carried out with the bolometric technique and an upper limit of 3×1024 y (@ 90%C.L.) is set for this process. Cuoricino represents not only the most sensitive DBD Experiment presently operating but also a prototype for a next generation experiment, CUORE (Cryogenic Underground Observatory for Rare Events). The expected performance and sensitivity, based on Monte Carlo simulations and extrapolations of the present Cuoricino results, indicate that CUORE will be able to test the 0.02-0.05 eV region for the effective neutrino mass, having a high discovery potential in the inverted hierarchy region of the neutrino mass pattern
Discovery potential of xenon-based neutrinoless double beta decay experiments in light of small angular scale CMB observations
The South Pole Telescope (SPT) has probed an expanded angular range of the CMB temperature power spectrum. Their recent analysis of the latest cosmological data prefers nonzero neutrino masses, mnu = 0.32+-0.11 eV. This result, if confirmed by the upcoming Planck data, has deep implications on the discovery of the nature of neutrinos. In particular, the values of the effective neutrino mass involved in neutrinoless double beta decay (bb0nu) are severely constrained for both the direct and inverse hierarchy, making a discovery much more likely. In this paper, we focus in xenon-based bb0nu experiments, on the double grounds of their good performance and the suitability of the technology to large-mass scaling. We show that the current generation, with effective masses in the range of 100 kg and conceivable exposures in the range of 500 kg year, could already have a sizable opportunity to observe bb0nu events, and their combined discovery potential is quite large. The next generation, with an exposure in the range of 10 ton year, would have a much more enhanced sensitivity, in particular due to the very low specific background that all the xenon technologies (liquid xenon, high-pressure xenon and xenon dissolved in liquid scintillator) can achieve. In addition, a high-pressure xenon gas TPC also features superb energy resolution. We show that such detector can fully explore the range of allowed effective Majorana masses, thus making a discovery very likely
A See-Saw model for fermion masses and mixings
We present a supersymmetric see-saw model giving rise to the most
general neutrino mass matrix compatible with Tri-Bimaximal mixing. We adopt the
flavour symmetry, broken by suitable vacuum expectation values
of a small number of flavon fields. We show that the vacuum alignment is a
natural solution of the most general superpotential allowed by the flavour
symmetry, without introducing any soft breaking terms. In the charged lepton
sector, mass hierarchies are controlled by the spontaneous breaking of the
flavour symmetry caused by the vevs of one doublet and one triplet flavon
fields instead of using the Froggatt-Nielsen U(1) mechanism. The next to
leading order corrections to both charged lepton mass matrix and flavon vevs
generate corrections to the mixing angles as large as .
Applied to the quark sector, the symmetry group can give a
leading order proportional to the identity as well as a matrix with
coefficients in the Cabibbo submatrix. Higher order
corrections produce non vanishing entries in the other entries which
are generically of .Comment: 30 pages, 3 figures, minor changes to match the published versio
CUORE-0 results and prospects for the CUORE experiment
With 741 kg of TeO2 crystals and an excellent energy resolution of 5 keV
(0.2%) at the region of interest, the CUORE (Cryogenic Underground Observatory
for Rare Events) experiment aims at searching for neutrinoless double beta
decay of 130Te with unprecedented sensitivity. Expected to start data taking in
2015, CUORE is currently in an advanced construction phase at LNGS. CUORE
projected neutrinoless double beta decay half-life sensitivity is 1.6E26 y at 1
sigma (9.5E25 y at the 90% confidence level), in five years of live time,
corresponding to an upper limit on the effective Majorana mass in the range
40-100 meV (50-130 meV). Further background rejection with auxiliary bolometric
detectors could improve CUORE sensitivity and competitiveness of bolometric
detectors towards a full analysis of the inverted neutrino mass hierarchy.
CUORE-0 was built to test and demonstrate the performance of the upcoming CUORE
experiment. It consists of a single CUORE tower (52 TeO2 bolometers of 750 g
each, arranged in a 13 floor structure) constructed strictly following CUORE
recipes both for materials and assembly procedures. An experiment its own,
CUORE-0 is expected to reach a sensitivity to the neutrinoless double beta
decay half-life of 130Te around 3E24 y in one year of live time. We present an
update of the data, corresponding to an exposure of 18.1 kg y. An analysis of
the background indicates that the CUORE performance goal is satisfied while the
sensitivity goal is within reach.Comment: 10 pages, 3 figures, to appear in the proceedings of NEUTRINO 2014,
26th International Conference on Neutrino Physics and Astrophysics, 2-7 June
2014, held at Boston, Massachusetts, US
Status of the CUORE and results from the CUORE-0 neutrinoless double beta decay experiments
CUORE is a 741 kg array of TeO2 bolometers for the search of neutrinoless
double beta decay of 130Te. The detector is being constructed at the Laboratori
Nazionali del Gran Sasso, Italy, where it will start taking data in 2015. If
the target background of 0.01 counts/keV/kg/y will be reached, in five years of
data taking CUORE will have a 1 sigma half life sensitivity of 10E26 y. CUORE-0
is a smaller experiment constructed to test and demonstrate the performances
expected for CUORE. The detector is a single tower of 52 CUORE-like bolometers
that started taking data in spring 2013. The status and perspectives of CUORE
will be discussed, and the first CUORE-0 data will be presented.Comment: 7 pages, 4 figures, to be published in the proceedings of ICHEP 2014,
37th International Conference on High Energy Physics, Valencia (Spain) 2-9
July 201
Measurement of the Two-Neutrino Double Beta Decay Half-life of Te with the CUORE-0 Experiment
We report on the measurement of the two-neutrino double beta decay half-life
of Te with the CUORE-0 detector. From an exposure of 33.4 kgy of
TeO, the half-life is determined to be = [8.2 0.2
(stat.) 0.6 (syst.)] 10y. This result is obtained after a
detailed reconstruction of the sources responsible for the CUORE-0 counting
rate, with a specific study of those contributing to the Te
neutrinoless double beta decay region of interest.Comment: Corrected typo in section 9: 3.43E5 Bq/kg should have read 3.43E-5
Bq/k
Analysis Techniques for the Evaluation of the Neutrinoless Double-Beta Decay Lifetime in Te with CUORE-0
We describe in detail the methods used to obtain the lower bound on the
lifetime of neutrinoless double-beta () decay in Te and
the associated limit on the effective Majorana mass of the neutrino using the
CUORE-0 detector. CUORE-0 is a bolometric detector array located at the
Laboratori Nazionali del Gran Sasso that was designed to validate the
background reduction techniques developed for CUORE, a next-generation
experiment scheduled to come online in 2016. CUORE-0 is also a competitive
decay search in its own right and functions as a platform to
further develop the analysis tools and procedures to be used in CUORE. These
include data collection, event selection and processing, as well as an
evaluation of signal efficiency. In particular, we describe the amplitude
evaluation, thermal gain stabilization, energy calibration methods, and the
analysis event selection used to create our final decay search
spectrum. We define our high level analysis procedures, with emphasis on the
new insights gained and challenges encountered. We outline in detail our
fitting methods near the hypothesized decay peak and catalog
the main sources of systematic uncertainty. Finally, we derive the
decay half-life limits previously reported for CUORE-0,
yr, and in combination with the Cuoricino
limit, yr.Comment: 18 pages, 18 figures. (Version 3 reflects only minor changes to the
text. Few additional details, no major content changes.
The projected background for the CUORE experiment
The Cryogenic Underground Observatory for Rare Events (CUORE) is designed to search for neutrinoless double beta decay of 130Te with an array of 988 TeO2 bolometers operating at temperatures around 10 mK. The experiment is currently being commissioned in Hall A of Laboratori Nazionali del Gran Sasso, Italy. The goal of CUORE is to reach a 90% C.L. exclusion sensitivity on the 130Te decay half-life of 9 × 1025 years after 5 years of data taking. The main issue to be addressed to accomplish this aim is the rate of background events in the region of interest, which must not be higher than 10- 2 counts/keV/kg/year. We developed a detailed Monte Carlo simulation, based on results from a campaign of material screening, radioassays, and bolometric measurements, to evaluate the expected background. This was used over the years to guide the construction strategies of the experiment and we use it here to project a background model for CUORE. In this paper we report the results of our study and our expectations for the background rate in the energy region where the peak signature of neutrinoless double beta decay of 130Te is expected
CUORE-0 detector: design, construction and operation
The CUORE experiment will search for neutrinoless double-beta decay ofTe with an array of 988 TeO bolometers arranged in 19 towers.CUORE-0, the first tower assembled according to the CUORE procedures, was builtand commissioned at Laboratori Nazionali del Gran Sasso, and took data fromMarch 2013 to March 2015. In this paper we describe the design, constructionand operation of the CUORE-0 experiment, with an emphasis on the improvementsmade over a predecessor experiment, Cuoricino. In particular, we demonstratewith CUORE-0 data that the design goals of CUORE are within reach