138 research outputs found
Solubility, Light Output and Energy Resolution Studies of Molybdenum-Loaded Liquid Scintillators
The search for neutrinoless double-beta decay is an important part of the
global neutrino physics program. One double-beta decay isotope currently under
investigation is 100Mo. In this article, we discuss the results of a
feasibility study investigating the use of molybdenum-loaded liquid
scintillator. A large, molybdenum-loaded liquid scintillator detector is one
potential design for a low-background, internal-source neutrinoless double-beta
decay search with 100Mo. The program outlined in this article included the
selection of a solute containing molybdenum, a scintillating solvent and the
evaluation of the mixture's performance as a radiation detector.Comment: 8 pages, 3 figure
Search for neutrinoless double beta decay with NEMO 3 experiment
NEMO 3 experiment is designed to search for neutrinoless double beta decay.
It is located in the Modane Underground Laboratory (LSM) and has been taking
data since February 2003. The half- lives of two neutrino beta decay have been
measured for seven isotopes. No evidence of neutrinoless double beta decay has
been found. The limits on both the half-lives of the neutrinoless double beta
decay and the corresponding Majorana effective masses are derivedComment: 3 pages, 2 figures, 2 tables, PANIC08 Conference proceeding
Results of NEMO 3 and status of SuperNEMO
The NEMO 3 experiment is devoted to the search for neutrinoless double beta
decay, as well as for accurate measurement of two-neutrino double beta decay.
The detector has been taking data in the LSM laboratory since 2003 and the
latest NEMO 3 results for seven double beta decay isotopes are presented here
for both decay modes. The SuperNEMO project aims to extend the NEMO technique
to a 100-200 kg isotope experiment with the target half-life sensitivity of 1-2
x 10^26 y. The current status of the SuperNEMO R&D programme is described.Comment: 3 pages, 2 tables, NOW 2008 conference proceeding
Investigation of double beta decay with the NEMO-3 detector
The double beta decay experiment NEMO~3 has been taking data since February
2003. The aim of this experiment is to search for neutrinoless
() decay and investigate two neutrino double beta decay in
seven different isotopically enriched samples (Mo, Se,
Ca, Zr, Cd, Te and Nd). After analysis of
the data corresponding to 3.75 y, no evidence for decay in the
Mo and Se samples was found. The half-life limits at the 90%
C.L. are y and y, respectively.
Additionally for decay the following limits at the 90% C.L.
were obtained, y for Ca, y
for Zr and y for Nd. The
decay half-life values were precisely measured for all investigated isotopes.Comment: 12 pages, 4 figures, 5 tables; talk at conference on "Fundamental
Interactions Physics" (ITEP, Moscow, November 23-27, 2009
CdWO4 scintillating bolometer for Double Beta Decay: Light and Heat anticorrelation, light yield and quenching factors
We report the performances of a 0.51 kg CdWO4 scintillating bolometer to be
used for future Double Beta Decay Experiments. The simultaneous read-out of the
heat and the scintillation light allows to discriminate between different
interacting particles aiming at the disentanglement and the reduction of
background contribution, key issue for next generation experiments. We will
describe the observed anticorrelation between the heat and the light signal and
we will show how this feature can be used in order to increase the energy
resolution of the bolometer over the entire energy spectrum, improving up to a
factor 2.6 on the 2615 keV line of 208Tl. The detector was tested in a 433 h
background measurement that permitted to estimate extremely low internal trace
contaminations of 232Th and 238U. The light yield of gamma/beta, alpha and
neutrons is presented. Furthermore we developed a method in order to correctly
evaluate the absolute thermal quenching factor of alpha particles in
scintillating bolometers.Comment: 8 pages 7 figure
On the Quantitative Impact of the Schechter-Valle Theorem
We evaluate the Schechter-Valle (Black Box) theorem quantitatively by
considering the most general Lorentz invariant Lagrangian consisting of
point-like operators for neutrinoless double beta decay. It is well known that
the Black Box operators induce Majorana neutrino masses at four-loop level.
This warrants the statement that an observation of neutrinoless double beta
decay guarantees the Majorana nature of neutrinos. We calculate these
radiatively generated masses and find that they are many orders of magnitude
smaller than the observed neutrino masses and splittings. Thus, some lepton
number violating New Physics (which may at tree-level not be related to
neutrino masses) may induce Black Box operators which can explain an observed
rate of neutrinoless double beta decay. Although these operators guarantee
finite Majorana neutrino masses, the smallness of the Black Box contributions
implies that other neutrino mass terms (Dirac or Majorana) must exist. If
neutrino masses have a significant Majorana contribution then this will become
the dominant part of the Black Box operator. However, neutrinos might also be
predominantly Dirac particles, while other lepton number violating New Physics
dominates neutrinoless double beta decay. Translating an observed rate of
neutrinoless double beta decay into neutrino masses would then be completely
misleading. Although the principal statement of the Schechter-Valle theorem
remains valid, we conclude that the Black Box diagram itself generates
radiatively only mass terms which are many orders of magnitude too small to
explain neutrino masses. Therefore, other operators must give the leading
contributions to neutrino masses, which could be of Dirac or Majorana nature.Comment: 18 pages, 4 figures; v2: minor corrections, reference added, matches
journal version; v3: typo corrected, physics result and conclusions unchange
Spectral modeling of scintillator for the NEMO-3 and SuperNEMO detectors
We have constructed a GEANT4-based detailed software model of photon
transport in plastic scintillator blocks and have used it to study the NEMO-3
and SuperNEMO calorimeters employed in experiments designed to search for
neutrinoless double beta decay. We compare our simulations to measurements
using conversion electrons from a calibration source of and show
that the agreement is improved if wavelength-dependent properties of the
calorimeter are taken into account. In this article, we briefly describe our
modeling approach and results of our studies.Comment: 16 pages, 10 figure
Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils
The development of BiPo detectors is dedicated to the measurement of
extremely high radiopurity in Tl and Bi for the SuperNEMO
double beta decay source foils. A modular prototype, called BiPo-1, with 0.8
of sensitive surface area, has been running in the Modane Underground
Laboratory since February, 2008. The goal of BiPo-1 is to measure the different
components of the background and in particular the surface radiopurity of the
plastic scintillators that make up the detector. The first phase of data
collection has been dedicated to the measurement of the radiopurity in
Tl. After more than one year of background measurement, a surface
activity of the scintillators of (Tl) 1.5
Bq/m is reported here. Given this level of background, a larger BiPo
detector having 12 m of active surface area, is able to qualify the
radiopurity of the SuperNEMO selenium double beta decay foils with the required
sensitivity of (Tl) 2 Bq/kg (90% C.L.) with a six
month measurement.Comment: 24 pages, submitted to N.I.M.
Probing New Physics Models of Neutrinoless Double Beta Decay with SuperNEMO
The possibility to probe new physics scenarios of light Majorana neutrino
exchange and right-handed currents at the planned next generation neutrinoless
double beta decay experiment SuperNEMO is discussed. Its ability to study
different isotopes and track the outgoing electrons provides the means to
discriminate different underlying mechanisms for the neutrinoless double beta
decay by measuring the decay half-life and the electron angular and energy
distributions.Comment: 17 pages, 14 figures, to be published in E.P.J.
Neutrinoless double beta decay in seesaw models
We study the general phenomenology of neutrinoless double beta decay in
seesaw models. In particular, we focus on the dependence of the neutrinoless
double beta decay rate on the mass of the extra states introduced to account
for the Majorana masses of light neutrinos. For this purpose, we compute the
nuclear matrix elements as functions of the mass of the mediating fermions and
estimate the associated uncertainties. We then discuss what can be inferred on
the seesaw model parameters in the different mass regimes and clarify how the
contribution of the light neutrinos should always be taken into account when
deriving bounds on the extra parameters. Conversely, the extra states can also
have a significant impact, cancelling the Standard Model neutrino contribution
for masses lighter than the nuclear scale and leading to vanishing neutrinoless
double beta decay amplitudes even if neutrinos are Majorana particles. We also
discuss how seesaw models could reconcile large rates of neutrinoless double
beta decay with more stringent cosmological bounds on neutrino masses.Comment: 34 pages, 5 eps figures and 1 axodraw figure. Final version published
in JHEP. NME results available in Appendi
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