arXiv subjects

D. Waters

Publications and source records attributed to D. Waters.

At least 19 recordsLinked to original sources

arXiv2025

Fabrication of thin planar radiopure foils with 82Se for the SuperNEMO Demonstrator

The SuperNEMO Demonstrator, designed to search for double beta decay using enriched 82Se, has been assembled in the Modane Underground Laboratory under the French Alps. Thin foils with radio - purified and enriched 82Se are installed centrally in the detector. A novel foil fabrication method has been developed, improving the radiopurity achieved in the previous generation experiment. It consists of wrapping standalone selenium pads in raw Mylar, combined with selenium purified by a new reverse-chromatography method. This paper describes the features of these foils, their fabrication process, the characterization results, and the integration of the foils into the SuperNEMO Demonstrator.

physics.ins-det↗

arXiv2025

The Impact of Helium Exposure on the PMTs of the SuperNEMO Experiment

The performance of Hamamatsu 8" photomultiplier tubes (PMTs) of the type used in the SuperNEMO neutrinoless double-beta decay experiment (R5912-MOD), is investigated as a function of exposure to helium (He) gas. Two PMTs were monitored for over a year, one exposed to varying concentrations of He, and the other kept in standard atmospheric conditions as a control. Both PMTs were exposed to light signals generated by a Bi-207 radioactive source that provided consistent large input PMT signals similar to those that are typical of the SuperNEMO experiment. The energy resolution of PMT signals corresponding to 1 MeV energy scale determined from the Bi-207 decay spectrum, shows a negligible degradation with He exposure; however the rate of after-pulsing shows a clear increase with He exposure, which is modelled and compared to diffusion theory. A method for reconstructing the partial pressure of He within the PMT and a method for determining the He breakdown point, are introduced. The implications for long-term SuperNEMO operations are briefly discussed.

physics.ins-det↗

arXiv2024

Calorimeter commissioning of the SuperNEMO Demonstrator

The SuperNEMO experiment is searching for neutrinoless double beta decay of \textsuperscript{82}Se, with the unique combination of a tracking detector and a segmented calorimeter. This feature allows to detect the two electrons emitted in the decay and measure their individual energy and angular distribution. The SuperNEMO calorimeter consists of 712 plastic scintillator blocks readout by large PMTs. After the construction of the demonstrator calorimeter underground, we have performed its first commissioning using $\gamma$-particles from calibration sources or from the ambient radioactive background. This article presents the quality assurance tests of the SuperNEMO demonstrator calorimeter and its first time and energy calibrations, with the associated methods.

physics.ins-det↗

arXiv2024

Determining Absolute Neutrino Mass using Quantum Technologies

Next generation tritium decay experiments to determine the absolute neutrino mass require high-precision measurements of $\beta$-decay electron energies close to the kinematic end point. To achieve this, the development of high phase-space density sources of atomic tritium is required, along with the implementation of methods to control the motion of these atoms to allow extended observation times. A promising approach to efficiently and accurately measure the kinetic energies of individual $\beta$-decay electrons generated in these dilute atomic gases, is to determine the frequency of the cyclotron radiation they emit in a precisely characterised magnetic field. This cyclotron radiation emission spectroscopy technique can benefit from recent developments in quantum technologies. Absolute static-field magnetometry and electrometry, which is essential for the precise determination of the electron kinetic energies from the frequency of their emitted cyclotron radiation, can be performed using atoms in superpositions of circular Rydberg states. Quantum-limited microwave amplifiers will allow precise cyclotron frequency measurements to be made with maximal signal-to-noise ratios and minimal observation times. Exploiting the opportunities offered by quantum technologies in these key areas, represents the core activity of the Quantum Technologies for Neutrino Mass project. Its goal is to develop a new experimental apparatus that can enable a determination of the absolute neutrino mass with a sensitivity on the order of 10~meV/$c^2$.

hep-ex↗

arXiv2022

Measurement of double-$\beta$ decay of $^{150}$Nd to the 0$^+_1$ excited state of $^{150}$Sm in NEMO-3

The NEMO-3 results for the double-$\beta$ decay of $^{150}$Nd to the 0$^+_1$ and 2$^+_1$ excited states of $^{150}$Sm are reported. The data recorded during 5.25 yr with 36.6 g of the isotope $^{150}$Nd are used in the analysis. For the first time, the signal of the $2\nu\beta\beta$ transition to the 0$^+_1$ excited state is detected with a statistical significance exceeding 5$\sigma$. The half-life is measured to be $T_{1/2}^{2\nu\beta\beta}(0^+_1) = \left[ 1.11 ^{+0.19}_{-0.14} \,\left(\mbox{stat}\right) ^{+0.17}_{-0.15}\, \left(\mbox{syst}\right) \right] \times10^{20}\,\mbox{yr}$. The limits are set on the $2\nu\beta\beta$ decay to the 2$^+_1$ level and on the $0\nu\beta\beta$ decay to the 0$^+_1$ and 2$^+_1$ levels of $^{150}$Sm.

nucl-ex↗

arXiv2021

Measurement of the distribution of $^{207}$Bi depositions on calibration sources for SuperNEMO

The SuperNEMO experiment will search for neutrinoless double-beta decay ($0\nu\beta\beta$), and study the Standard-Model double-beta decay process ($2\nu\beta\beta$). The SuperNEMO technology can measure the energy of each of the electrons produced in a double-beta ($\beta\beta$) decay, and can reconstruct the topology of their individual tracks. The study of the double-beta decay spectrum requires very accurate energy calibration to be carried out periodically. The SuperNEMO Demonstrator Module will be calibrated using 42 calibration sources, each consisting of a droplet of $^{207}$Bi within a frame assembly. The quality of these sources, which depends upon the entire $^{207}$Bi droplet being contained within the frame, is key for correctly calibrating SuperNEMO's energy response. In this paper, we present a novel method for precisely measuring the exact geometry of the deposition of $^{207}$Bi droplets within the frames, using Timepix pixel detectors. We studied 49 different sources and selected 42 high-quality sources with the most central source positioning.

physics.ins-det↗

arXiv2018

Final results on $^\textbf{82}$Se double beta decay to the ground state of $^\textbf{82}$Kr from the NEMO-3 experiment

Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ($2\nu\beta\beta$) half-life of $^{82}$Se as $T_{1/2}^{2\nu} = \left[ 9.39 \pm 0.17\,\left(\mbox{stat}\right) \pm 0.58\,\left(\mbox{syst}\right)\right] \times 10^{19}$ y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is $\left|M^{2\nu}\right| = 0.0498 \pm 0.0016$. In addition, a search for neutrinoless double beta decay ($0\nu\beta\beta$) using 0.93 kg of $^{82}$Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of $T_{1/2}^{0\nu} > 2.5 \times 10^{23} \,\mbox{y} \,(90\%\,\mbox{C.L.})$ for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of $\langle m_{\nu} \rangle < \left(1.2 - 3.0\right) \,\mbox{eV}$, where the range reflects $0\nu\beta\beta$ nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other $0\nu\beta\beta$ mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.

hep-ex↗

arXiv2017

Calorimeter development for the SuperNEMO double beta decay experiment

SuperNEMO is a double-$\beta$ decay experiment, which will employ the successful tracker-calorimeter technique used in the recently completed NEMO-3 experiment. SuperNEMO will implement 100 kg of double-$\beta$ decay isotope, reaching a sensitivity to the neutrinoless double-$\beta$ decay ($0\nu\beta\beta$) half-life of the order of $10^{26}$ yr, corresponding to a Majorana neutrino mass of 50-100 meV. One of the main goals and challenges of the SuperNEMO detector development programme has been to reach a calorimeter energy resolution, $\Delta$E/E, around 3%/$sqrt(E)$(MeV) $\sigma$, or 7%/$sqrt(E)$(MeV) FWHM (full width at half maximum), using a calorimeter composed of large volume plastic scintillator blocks coupled to photomultiplier tubes. We describe the R\&D programme and the final design of the SuperNEMO calorimeter that has met this challenging goal.

physics.ins-det↗

arXiv2017

Search for neutrinoless quadruple-$\beta$ decay of $^{150}$Nd with the NEMO-3 detector

We report the results of a first experimental search for lepton number violation by four units in the neutrinoless quadruple-$\beta$ decay of $^{150}$Nd using a total exposure of $0.19$ kg$\cdot$y recorded with the NEMO-3 detector at the Modane Underground Laboratory (LSM). We find no evidence of this decay and set lower limits on the half-life in the range $T_{1/2}>(1.1-3.2)\times10^{21}$ y at the $90\%$ CL, depending on the model used for the kinematic distributions of the emitted electrons.

hep-ex↗

arXiv2017

The BiPo-3 detector for the measurement of ultra low natural radioactivities of thin materials

The BiPo-3 detector, running in the Canfranc Underground Laboratory (Laboratorio Subterr\'aneo de Canfranc, LSC, Spain) since 2013, is a low-radioactivity detector dedicated to measuring ultra low natural radionuclide contaminations of $^{208}$Tl ($^{232}$Th chain) and $^{214}$Bi ($^{238}$U chain) in thin materials. The total sensitive surface area of the detector is 3.6 m$^2$. The detector has been developed to measure radiopurity of the selenium double $\beta$-decay source foils of the SuperNEMO experiment. In this paper the design and performance of the detector, and results of the background measurements in $^{208}$Tl and $^{214}$Bi, are presented, and validation of the BiPo-3 measurement with a calibrated aluminium foil is discussed. Results of the $^{208}$Tl and $^{214}$Bi activity measurements of the first enriched $^{82}$Se foils of the double $\beta$-decay SuperNEMO experiment are reported. The sensitivity of the BiPo-3 detector for the measurement of the SuperNEMO $^{82}$Se foils is $\mathcal{A}$($^{208}$Tl) $<2$ $\mu$Bq/kg (90\% C.L.) and $\mathcal{A}$($^{214}$Bi) $<140$ $\mu$Bq/kg (90\% C.L.) after 6 months of measurement.

physics.ins-det↗

arXiv2016

Measurement of the $2\nu\beta\beta$ Decay Half-Life and Search for the $0\nu\beta\beta$ Decay of $^{116}$Cd with the NEMO-3 Detector

The NEMO-3 experiment measured the half-life of the $2\nu\beta\beta$ decay and searched for the $0\nu\beta\beta$ decay of $^{116}$Cd. Using $410$ g of $^{116}$Cd installed in the detector with an exposure of $5.26$ y, ($4968\pm74$) events corresponding to the $2\nu\beta\beta$ decay of $^{116}$Cd to the ground state of $^{116}$Sn have been observed with a signal to background ratio of about $12$. The half-life of the $2\nu\beta\beta$ decay has been measured to be $ T_{1/2}^{2\nu}=[2.74\pm0.04\mbox{(stat.)}\pm0.18\mbox{(syst.)}]\times10^{19}$ y. No events have been observed above the expected background while searching for $0\nu\beta\beta$ decay. The corresponding limit on the half-life is determined to be $T_{1/2}^{0\nu} \ge 1.0 \times 10^{23}$ y at the $90$ % C.L. which corresponds to an upper limit on the effective Majorana neutrino mass of $\langle m_{\nu} \rangle \le 1.4-2.5$ eV depending on the nuclear matrix elements considered. Limits on other mechanisms generating $0\nu\beta\beta$ decay such as the exchange of R-parity violating supersymmetric particles, right-handed currents and majoron emission are also obtained.

hep-ex↗

arXiv2016

Measurement of the 2$\nu\beta\beta$ decay half-life of $^{150}$Nd and a search for 0$\nu\beta\beta$ decay processes with the full exposure from the NEMO-3 detector

We present results from a search for neutrinoless double-$\beta$ ($0\nu\beta\beta$) decay using 36.6 g of the isotope $^{150}$Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a complete background model for this isotope, including a measurement of the two-neutrino double-$\beta$ decay half-life of $T^{2\nu}_{1/2}=$[9.34 $\pm$ 0.22 (stat.) $^{+0.62}_{-0.60}$ (syst.)]$\times 10^{18}$ y for the ground state transition, which represents the most precise result to date for this isotope. We perform a multivariate analysis to search for \zeronu decays in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay mechanisms. As no evidence for \zeronu decay is observed, we derive lower limits on half-lives for several mechanisms involving physics beyond the Standard Model. The observed lower limit, assuming light Majorana neutrino exchange mediates the decay, is $T^{0\nu}_{1/2} >$ 2.0 $\times 10^{22}$ y at the 90% C.L., corresponding to an upper limit on the effective neutrino mass of $\langle m_{\nu} \rangle$ $<$ 1.6 - 5.3 eV..

hep-ex↗

arXiv2016

Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of $^{48}{\rm Ca}$ with the NEMO-3 detector

The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-$\beta$ decay of $^{48}{\rm Ca}$. Using $5.25$ yr of data recorded with a $6.99\,{\rm g}$ sample of $^{48}{\rm Ca}$, approximately $150$ double-$\beta$ decay candidate events have been selected with a signal-to-background ratio greater than $3$. The half-life for the two-neutrino double-$\beta$ decay of $^{48}{\rm Ca}$ has been measured to be $T^{2\nu}_{1/2}\,=\,[6.4\, ^{+0.7}_{-0.6}{\rm (stat.)} \, ^{+1.2}_{-0.9}{\rm (syst.)}] \times 10^{19}\,{\rm yr}$. A search for neutrinoless double-$\beta$ decay of $^{48}{\rm Ca}$ yields a null result and a corresponding lower limit on the half-life is found to be $T^{0\nu}_{1/2} > 2.0 \times 10^{22}\,{\rm yr}$ at $90\%$ confidence level, translating into an upper limit on the effective Majorana neutrino mass of $< m_{\beta\beta} > < 6.0 - 26$ ${\rm eV}$, with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.

hep-ex↗

arXiv2015

Result of the search for neutrinoless double-$\beta$ decay in $^{100}$Mo with the NEMO-3 experiment

The NEMO-3 detector, which had been operating in the Modane Underground Laboratory from 2003 to 2010, was designed to search for neutrinoless double $\beta$ ($0\nu\beta\beta$) decay. We report final results of a search for $0\nu\beta\beta$ decays with $6.914$ kg of $^{100}$Mo using the entire NEMO-3 data set with a detector live time of $4.96$ yr, which corresponds to an exposure of 34.3 kg$\cdot$yr. We perform a detailed study of the expected background in the $0\nu\beta\beta$ signal region and find no evidence of $0\nu\beta\beta$ decays in the data. The level of observed background in the $0\nu\beta\beta$ signal region $[2.8-3.2]$ MeV is $0.44 \pm 0.13$ counts/yr/kg, and no events are observed in the interval $[3.2-10]$ MeV. We therefore derive a lower limit on the half-life of $0\nu\beta\beta$ decays in $^{100}$Mo of $T_{1/2}(0\nu\beta\beta)> 1.1 \times 10^{24}$ yr at the $90\%$ Confidence Level, under the hypothesis of light Majorana neutrino exchange. Depending on the model used for calculating nuclear matrix elements, the limit for the effective Majorana neutrino mass lies in the range $\langle m_{\nu} \rangle < 0.33$--$0.62$ eV. We also report constraints on other lepton-number violating mechanisms for $0\nu\beta\beta$ decays.

hep-ex↗

arXiv2014

Search for Neutrinoless Double-Beta Decay of $^{100}$Mo with the NEMO-3 Detector

We report the results of a search for the neutrinoless double-$β$ decay (0$νββ$) of $^{100}$Mo, using the NEMO-3 detector to reconstruct the full topology of the final state events. With an exposure of 34.7 kg.y, no evidence for the 0$νββ$ signal has been found, yielding a limit for the light Majorana neutrino mass mechanism of $T_{1/2}(0νββ)>1.1 \times 10^{24}$ years (90% C.L.) once both statistical and systematic uncertainties are taken into account. Depending on the Nuclear Matrix Elements this corresponds to an upper limit on the Majorana effective neutrino mass of $< m_ν > < 0.3-0.9$ eV (90% C.L.). Constraints on other lepton number violating mechanisms of 0$νββ$ decays are also given. Searching for high-energy double electron events in all suitable sources of the detector, no event in the energy region [3.2-10] MeV is observed for an exposure of 47 kg.y.

hep-ex↗

arXiv2010

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.

hep-ex↗

arXiv2010

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 $\rm ^{207}Bi$ 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.

physics.ins-det↗

arXiv2010

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 $^{208}$Tl and $^{214}$Bi for the SuperNEMO double beta decay source foils. A modular prototype, called BiPo-1, with 0.8 $m^2$ 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 $^{208}$Tl. After more than one year of background measurement, a surface activity of the scintillators of $\mathcal{A}$($^{208}$Tl) $=$ 1.5 $μ$Bq/m$^2$ is reported here. Given this level of background, a larger BiPo detector having 12 m$^2$ of active surface area, is able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of $\mathcal{A}$($^{208}$Tl) $<$ 2 $μ$Bq/kg (90% C.L.) with a six month measurement.

physics.ins-det↗