97 research outputs found
Indirect Signatures of Type I See-Saw Scenarios
We consider the low energy constraints that can be applied to type I see-saw
extensions of the Standard Model in which the right-handed neutrinos are taken
at the electroweak scale. In the reported scenarios, the flavour structure of
the charged current and neutral current weak interactions of the Standard Model
leptons with the heavy right-handed neutrinos is essentially determined by the
neutrino oscillation parameters. In this case, correlations among different
measurable phenomena in the lepton sector may provide compelling indirect
evidence of low energy see-saw mechanism of neutrino mass generation.Comment: 4 pages, 2 figures. Contributions to the Proceedings of the 12th
International Conference on Topics in Astroparticle and Underground Physics
(TAUP 2011), Munich, Germany, 5-9 September 201
Improvement of the energy resolution via an optimized digital signal processing in GERDA Phase I
An optimized digital shaping filter has been developed for the Gerda experiment which searches for neutrinoless double beta decay in Ge. The Gerda Phase I energy calibration data have been reprocessed and an average improvement of 0.3 keV in energy resolution (FWHM) corresponding to 10 % at the value for decay in Ge is obtained. This is possible thanks to the enhanced low-frequency noise rejection of this Zero Area Cusp (ZAC) signal shaping filter.Peer Reviewe
Dynamical Dark Energy model parameters with or without massive neutrinos
We use WMAP5 and other cosmological data to constrain model parameters in
quintessence cosmologies, focusing also on their shift when we allow for
non-vanishing neutrino masses. The Ratra-Peebles (RP) and SUGRA potentials are
used here, as examples of slowly or fastly varying state parameter w(a). Both
potentials depend on an energy scale \Lambda. Here we confirm the results of
previous analysis with WMAP3 data on the upper limits on \Lambda, which turn
out to be rather small (down to ~10^{-9} in RP cosmologies and ~10^{-5} for
SUGRA). Our constraints on \Lambda are not heavily affected by the inclusion of
neutrino mass as a free parameter. On the contrary, when the neutrino mass
degree of freedom is opened, significant shifts in the best-fit values of other
parameters occur.Comment: 9 pages, 3 figures, submitted to JCA
Pulse shape discrimination studies with a Broad-Energy Germanium detector for signal identification and background suppression in the GERDA double beta decay experiment
First studies of event discrimination with a Broad-Energy Germanium (BEGe)
detector are presented. A novel pulse shape method, exploiting the
characteristic electrical field distribution inside BEGe detectors, allows to
identify efficiently single-site events and to reject multi-site events. The
first are typical for neutrinoless double beta decays (0-nu-2-beta) and the
latter for backgrounds from gamma-ray interactions. The obtained survival
probabilities of backgrounds at energies close to Q(76Ge) = 2039 keV are 0.93%
for events from 60Co, 21% from 226Ra and 40% from 228Th. This background
suppression is achieved with 89% acceptance of 228Th double escape events,
which are dominated by single site interactions. Approximately equal acceptance
is expected for 0-nu-2-beta-decay events. Collimated beam and Compton
coincidence measurements demonstrate that the discrimination is largely
independent of the interaction location inside the crystal and validate the
pulse-shape cut in the energy range of Q(76Ge). The application of BEGe
detectors in the GERDA and the Majorana double beta decay experiments is under
study.Comment: 22 pages, 16 figures, submitted to JINST: JINST_018P_080
Pulse shape discrimination studies with a Broad-Energy Germanium detector for signal identification and background suppression in the GERDA double beta decay experiment
First studies of event discrimination with a Broad-Energy Germanium (BEGe)
detector are presented. A novel pulse shape method, exploiting the
characteristic electrical field distribution inside BEGe detectors, allows to
identify efficiently single-site events and to reject multi-site events. The
first are typical for neutrinoless double beta decays (0-nu-2-beta) and the
latter for backgrounds from gamma-ray interactions. The obtained survival
probabilities of backgrounds at energies close to Q(76Ge) = 2039 keV are 0.93%
for events from 60Co, 21% from 226Ra and 40% from 228Th. This background
suppression is achieved with 89% acceptance of 228Th double escape events,
which are dominated by single site interactions. Approximately equal acceptance
is expected for 0-nu-2-beta-decay events. Collimated beam and Compton
coincidence measurements demonstrate that the discrimination is largely
independent of the interaction location inside the crystal and validate the
pulse-shape cut in the energy range of Q(76Ge). The application of BEGe
detectors in the GERDA and the Majorana double beta decay experiments is under
study.Comment: 22 pages, 16 figures, submitted to JINST: JINST_018P_080
Pulse shape discrimination studies with a Broad-Energy Germanium detector for signal identification and background suppression in the GERDA double beta decay experiment
First studies of event discrimination with a Broad-Energy Germanium (BEGe)
detector are presented. A novel pulse shape method, exploiting the
characteristic electrical field distribution inside BEGe detectors, allows to
identify efficiently single-site events and to reject multi-site events. The
first are typical for neutrinoless double beta decays (0-nu-2-beta) and the
latter for backgrounds from gamma-ray interactions. The obtained survival
probabilities of backgrounds at energies close to Q(76Ge) = 2039 keV are 0.93%
for events from 60Co, 21% from 226Ra and 40% from 228Th. This background
suppression is achieved with 89% acceptance of 228Th double escape events,
which are dominated by single site interactions. Approximately equal acceptance
is expected for 0-nu-2-beta-decay events. Collimated beam and Compton
coincidence measurements demonstrate that the discrimination is largely
independent of the interaction location inside the crystal and validate the
pulse-shape cut in the energy range of Q(76Ge). The application of BEGe
detectors in the GERDA and the Majorana double beta decay experiments is under
study.Comment: 22 pages, 16 figures, submitted to JINST: JINST_018P_080
The MGDO software library for data analysis in Ge neutrinoless double-beta decay experiments
The GERDA and Majorana experiments will search for neutrinoless double-beta
decay of germanium-76 using isotopically enriched high-purity germanium
detectors. Although the experiments differ in conceptual design, they share
many aspects in common, and in particular will employ similar data analysis
techniques. The collaborations are jointly developing a C++ software library,
MGDO, which contains a set of data objects and interfaces to encapsulate, store
and manage physical quantities of interest, such as waveforms and high-purity
germanium detector geometries. These data objects define a common format for
persistent data, whether it is generated by Monte Carlo simulations or an
experimental apparatus, to reduce code duplication and to ease the exchange of
information between detector systems. MGDO also includes general-purpose
analysis tools that can be used for the processing of measured or simulated
digital signals. The MGDO design is based on the Object-Oriented programming
paradigm and is very flexible, allowing for easy extension and customization of
the components. The tools provided by the MGDO libraries are used by both GERDA
and Majorana.Comment: 4 pages, 1 figure, proceedings for TAUP201
Signal modeling of high-purity Ge detectors with a small read-out electrode and application to neutrinoless double beta decay search in Ge-76
The GERDA experiment searches for the neutrinoless double beta decay of Ge-76
using high-purity germanium detectors enriched in Ge-76. The analysis of the
signal time structure provides a powerful tool to identify neutrinoless double
beta decay events and to discriminate them from gamma-ray induced backgrounds.
Enhanced pulse shape discrimination capabilities of "Broad Energy Germanium"
detectors with a small read-out electrode have been recently reported. This
paper describes the full simulation of the response of such a detector,
including the Monte Carlo modeling of radiation interaction and subsequent
signal shape calculation. A pulse shape discrimination method based on the
ratio between the maximum current signal amplitude and the event energy applied
to the simulated data shows quantitative agreement with the experimental data
acquired with calibration sources. The simulation has been used to study the
survival probabilities of the decays which occur inside the detector volume and
are difficult to assess experimentally. Such internal decay events are produced
by the cosmogenic radio-isotopes Ge-68 and Co-60 and the neutrinoless double
beta decay of Ge-76. Fixing the experimental acceptance of the double escape
peak of the 2.614 MeV photon to 90%, the estimated survival probabilities at
Qbb = 2.039 MeV are (86+-3)% for Ge-76 neutrinoless double beta decays,
(4.5+-0.3)% for the Ge-68 daughter Ga-68, and (0.9+0.4-0.2)% for Co-60 decays.Comment: 27 pages, 17 figures. v2: fixed typos and references. Submitted to
JINS
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
Majorana Neutrino Mixing
The most plausible see-saw explanation of the smallness of the neutrino
masses is based on the assumption that total lepton number is violated at a
large scale and neutrinos with definite masses are Majorana particles. In this
review we consider in details difference between Dirac and Majorana neutrino
mixing and possibilities of revealing Majorana nature of neutrinos with
definite masses
- …