20 research outputs found
Measurement of double beta decay of ¹⁰⁰Mo to excited states in the NEMO 3 experiment
The double beta decay of ¹⁰⁰Mo to the 0_{1}^{+} and 2_{1}^{+} excited states of ¹⁰⁰Ru is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta decay of ¹⁰⁰Mo to the excited 0_{1}^{+} state is measured to be T_{1/2}^{2v} = [5.7_{-0.9}^{+1.3} (stat.) ± 0.8 (syst.)] x 10²⁰ y. The signal-to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited 0_{1}^{+} state has been found. The corresponding half-life limit is T_{1/2}^{0v} (0⁺→0_{1}^{+}) > 8.9 x 10²² y (at 90% C.L.). The search for the double beta decay to the 2_{1}^{+} excited state has allowed the determination of limits on the half-life for the two neutrino mode T_{1/2}^{0v} (0⁺→2_{1}^{+}) > 1.1 x 10²¹ y (at 90% C.L.) and for the neutrinoless mode T_{1/2}^{0v} (0⁺→2_{1}^{+}) > 1.6 x 10²³ y (at 90% C.L.)
Measurement of double beta decay of 100Mo to excited states in the NEMO 3 experiment
The double beta decay of 100Mo to the 0^+_1 and 2^+_1 excited states of 100Ru
is studied using the NEMO 3 data. After the analysis of 8024 h of data the
half-life for the two-neutrino double beta decay of 100Mo to the excited 0^+_1
state is measured to be T^(2nu)_1/2 = [5.7^{+1.3}_{-0.9}(stat)+/-0.8(syst)]x
10^20 y. The signal-to-background ratio is equal to 3. Information about energy
and angular distributions of emitted electrons is also obtained. No evidence
for neutrinoless double beta decay to the excited 0^+_1 state has been found.
The corresponding half-life limit is T^(0nu)_1/2(0^+ --> 0^+_1) > 8.9 x 10^22 y
(at 90% C.L.).
The search for the double beta decay to the 2^+_1 excited state has allowed
the determination of limits on the half-life for the two neutrino mode
T^(2nu)_1/2(0^+ --> 2^+_1) > 1.1 x 10^21 y (at 90% C.L.) and for the
neutrinoless mode T^(0nu)_1/2(0^+ --> 2^+_1) > 1.6 x 10^23 y (at 90% C.L.).Comment: 23 pages, 7 figures, 4 tables, submitted to Nucl. Phy
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.
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
A large‑scale comparison of reproduction and recruitment of the stalked barnacle Pollicipes pollicipes across Europe
Understanding large-scale spatial and temporal patterns of marine populations is a central goal in ecology, which has received
renewed attention under climate change. However, few studies explore the large-scale dynamics of populations using standardized
protocols and during the same time frames. We studied the phenology and intensity of reproduction and recruitment
for the intertidal stalked barnacle Pollicipes pollicipes over an European scale and described their potential linkages with
environmental variables. This species supports profitable fisheries in the Iberian Peninsula (Spain and Portugal). In Brittany
(France), we had observed a significant lower reproductive effort (long non-breeding season, short breeding period in summer)
and low values of recruitment intensity. This pattern may be related to the fact that Brittany corresponds to the northern
limit of the distribution of this species in continental Europe. On the Iberian Peninsula, the most different region was Galicia
(Spain), with Asturias (Spain) and SW Portugal being more similar. In Galicia, we have observed a contradictory pattern
characterized by the absence of a non-breeding period and by a shorter recruitment season than observed in other Iberian
regions. Our results suggest that air temperature, SST and chlorophyll-a might be related to the variability in reproduction
and recruitment patterns of P. pollicipes. Moreover, spring and early summer upwelling in SW Portugal and Galicia might
be inhibiting recruitment in this period. At the northern limit, the expected increase in performance under climate change
might facilitate the recovery of populations after exploitation, increasing the resilience of the resource to fishing pressure
Measurement of the beta beta Decay Half-Life of Te-130 with the NEMO-3 Detector
We report results from the NEMO-3 experiment based on an exposure of 1275 days with 661 g of Te-130 in the form of enriched and natural tellurium foils. The beta beta decay rate of Te-130 is found to be greater than zero with a significance of 7.7 standard deviations and the half-life is measured to be T-1/2(2v)=[7.0 +/- 0.9(stat) +/- 1: 1(syst)] x 10(20) yr. This represents the most precise measurement of this half- life yet published and the first real-time observation of this decay
Technical performance of the NEMO 3 detector "Advantages and limitations"
The development of the NEMO 3 detector, which is now running in the Fréjus Underground Laboratory (L.S.M. Laboratoire Souterrain de Modane), was begun more than ten years ago. The NEMO 3 detector uses a tracking-calorimeter technique in order to investigate double beta decay processes for several isotopes. The technical description of the detector is followed by the presentation of its performance, including the methods used by the collaboration to address the radon problem