arXiv subjects

J. Mason

Publications and source records attributed to J. Mason.

17 recordsLinked to original sources

arXiv2026

Measurement of the muon flux at SNOLAB using the DEAP-3600 experiment

A direct measurement of the muon flux at SNOLAB is performed using the DEAP-3600 experiment, located 2 km underground at SNOLAB near Sudbury, Canada. Primarily designed for the direct detection of weakly interacting massive particles (WIMPs), a dark matter candidate, DEAP-3600 consists of an inner spherical acrylic vessel containing a liquid argon target; this vessel is enclosed within a steel shell which is submerged in an instrumented water tank, serving as a muon veto for the dark matter search. The muon flux measurement is performed using a cut-and-count analysis of events observed in the muon veto detector and of events which are coincident between the muon veto and the liquid argon target. The requirement that muons traverse both the water and liquid argon minimizes instrumental backgrounds and systematic uncertainties. Using data collected from November 2016 to March 2020, the muon flux is measured by this coincidence analysis to be $(3.71 \pm 0.25_{\textrm{stat}} \pm 0.09_{\textrm{sys}}) \times 10^{-10}\, \mu/$cm$^2$/s. The standalone measurement using muon veto data only is compatible within uncertainties. Both measurements agree with the previous result by the SNO experiment and with simulations carried out using the MUTE software. These results provide an important benchmark for future rare-event searches at the SNOLAB facility.

hep-ex↗

arXiv2026

First evidence of neutrino absorption on argon using $^{8}$B solar neutrinos in DEAP-3600

We report experimental evidence for electron neutrino charged-current interactions (neutrino absorption, CC $\nu_e$) from $^{8}$B solar neutrinos on $^{40}$Ar using an exposure of ($7.29 \pm 0.05$) tonne$\cdot$years in the DEAP-3600 detector. A region of interest (ROI) of 10.5-13.0 MeV reconstructed energy calibrated on single-peak events, corresponding to incident neutrino energy in 12.0-14.5 MeV, is used for this measurement. We observe 5 single-peak and 1 double-peak neutrino-like events consistent with the $^{8}$B solar neutrino energy spectrum in the ROI after correcting for nonlinearities in the detector response at high energies. With an expected background of $0.48~^{+0.16}_{-0.15}$ events, the data correspond to a significance of $4.0\,\sigma$ with respect to the background-only hypothesis. We report an energy-averaged cross section of $(4.0~^{+2.0}_{-1.6}~\mathrm{(stat)}~^{+0.8}_{-0.7}~\mathrm{(sys)})\times 10^{-41}\,\mathrm{cm}^2$ in the ROI for the CC $\nu_{e}$ signal, a factor $(2.4~^{+1.3}_{-1.0})$ higher than predicted by Bhattacharya, Goodman and Garc\'ia (2009).

hep-ex↗

arXiv2026

Dark Matter Search with the DEAP-3600 Detector using the Profile Likelihood Ratio Method

We present here a search for WIMP dark matter using 790.8 live-days of data collected with 3269 kg of liquid argon (1266 kg fiducial) by the DEAP-3600 detector at SNOLAB, using the Profile Likelihood Ratio method. The likelihood model is based on three parameters: estimated energy, pulse-shape discrimination parameter, and reconstructed position within the detector. Using this method, the expected signal sensitivity of DEAP-3600 benefits from an increased fiducial volume and improved event selection acceptance. Alpha-decays from a small number of dust particulates circulating within the liquid argon target are the dominant source of background events and limit the sensitivity of this search. This result provides improved exclusion upper limits on the WIMP-nucleon spin-independent cross section on liquid argon for WIMP masses between 20 GeV/$c^{2}$ and 100 GeV/$c^{2}$. At 100 GeV/$c^{2}$ the observed limit is 3.4 $\times$ 10$^{-45}$ cm$^2$ at 90% confidence level.

hep-ex↗

arXiv2025

Position Reconstruction in the DEAP-3600 Dark Matter Search Experiment

In the DEAP-3600 dark matter search experiment, precise reconstruction of the positions of scattering events in liquid argon is key for background rejection and defining a fiducial volume that enhances dark matter candidate events identification. This paper describes three distinct position reconstruction algorithms employed by DEAP-3600, leveraging the spatial and temporal information provided by photomultipliers surrounding a spherical liquid argon vessel. Two of these methods are maximum-likelihood algorithms: the first uses the spatial distribution of detected photoelectrons, while the second incorporates timing information from the detected scintillation light. Additionally, a machine learning approach based on the pattern of photoelectron counts across the photomultipliers is explored.

physics.ins-det↗

arXiv2025

Direct Measurement of the $^{39}$Ar Half-life from 3.4 Years of Data with the DEAP-3600 Detector

The half-life of $^{39}$Ar is measured using the DEAP-3600 detector located 2 km underground at SNOLAB. Between 2016 and 2020, DEAP-3600 used a target mass of (3269 $\pm$ 24) kg of liquid argon distilled from the atmosphere in a direct-detection dark matter search. Such an argon mass also enables direct measurements of argon isotope properties. The decay of $^{39}$Ar in DEAP-3600 is the dominant source of triggers by two orders of magnitude, ensuring high statistics and making DEAP-3600 well-suited for measuring this isotope's half-life. Use of the pulse-shape discrimination technique in DEAP-3600 allows powerful discrimination between nuclear recoils and electron recoils, resulting in the selection of a clean sample of $^{39}$Ar decays. Observing over a period of 3.4 years, the $^{39}$Ar half-life is measured to be $(302 \pm 8_{\rm stat} \pm 6_{\rm sys})$ years. This new direct measurement suggests that the half-life of $^{39}$Ar is significantly longer than the accepted value, with potential implications for measurements using this isotope's half-life as input.

nucl-ex↗

arXiv2024

Relative Measurement and Extrapolation of the Scintillation Quenching Factor of $\alpha$-Particles in Liquid Argon using DEAP-3600 Data

The knowledge of scintillation quenching of $\alpha$-particles plays a paramount role in understanding $\alpha$-induced backgrounds and improving the sensitivity of liquid argon-based direct detection of dark matter experiments. We performed a relative measurement of scintillation quenching in the MeV energy region using radioactive isotopes ($^{222}$Rn, $^{218}$Po and $^{214}$Po isotopes) present in trace amounts in the DEAP-3600 detector and quantified the uncertainty of extrapolating the quenching factor to the low-energy region.

physics.ins-det↗

arXiv2023

Precision Measurement of the Specific Activity of $^{39}$Ar in Atmospheric Argon with the DEAP-3600 Detector

The specific activity of the beta decay of $^{39}$Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 $\pm$ 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector with very low background uses pulseshape discrimination to differentiate between nuclear recoils and electron recoils and is well-suited to measure the decay of $^{39}$Ar. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is [0.964 $\pm$ 0.001 (stat) $\pm$ 0.024 (sys)] Bq/kg$_{\rm atmAr}$ which is consistent with results from other experiments. A cross-check analysis using different event selection criteria provides a consistent result.

physics.ins-det↗

arXiv2022

The Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) Mission: Motivation and Overview

The Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission is an astrophysics Small Explorer employing ultraviolet spectroscopy (EUV: 80 - 825 \AA\ and FUV: 1280 - 1650 \AA) to explore the high-energy radiation environment in the habitable zones around nearby stars. ESCAPE provides the first comprehensive study of the stellar EUV and coronal mass ejection environments which directly impact the habitability of rocky exoplanets. In a 20 month science mission, ESCAPE will provide the essential stellar characterization to identify exoplanetary systems most conducive to habitability and provide a roadmap for NASA's future life-finder missions. ESCAPE accomplishes this goal with roughly two-order-of-magnitude gains in EUV efficiency over previous missions. ESCAPE employs a grazing incidence telescope that feeds an EUV and FUV spectrograph. The ESCAPE science instrument builds on previous ultraviolet and X-ray instrumentation, grazing incidence optical systems, and photon-counting ultraviolet detectors used on NASA astrophysics, heliophysics, and planetary science missions. The ESCAPE spacecraft bus is the versatile and high-heritage Ball Aerospace BCP Small spacecraft. Data archives will be housed at the Mikulski Archive for Space Telescopes (MAST).

astro-ph.IM↗

arXiv2021

Ultraviolet-induced fluorescence of poly(methyl methacrylate) compared to 1,1,4,4-tetraphenyl-1,3-butadiene down to 4 K

Several particle-physics experiments use poly(methyl methacrylate) (a.k.a. PMMA or acrylic) vessels to contain liquid scintillators. Superluminal charged particles emitted from radioactive impurities in or near the acrylic can emit Cherenkov radiation in the ultraviolet (UV) spectra range. If acrylic fluoresces in the visible range due to this UV light, it could be a source of background in experiments where the main signal is visible scintillation light, or UV scintillation light that is absorbed and re-emitted at visible wavelengths by a wavelength shifter. Some of these experiments operate at low temperature. The fluorescence of these materials could change with temperature so we have studied the fluorescence of the acrylic used in the DEAP-3600 experiment down to a temperature of 4 K, and compared it to the common wavelength shifter 1,1,4,4-tetraphenyl-1,3-butadiene (TPB). The light yield and wavelength spectra of these materials were characterized by exciting the sample with 285 nm UV light which acted as a proxy for Cherenkov light in the detector. Spectral measurements indicate at least part of the fluorescence of the acrylic is due to additives. Time-resolved measurements show the light yields of our acrylic sample, TPB sample, and the relative light between both samples, all increase when cooling down. At room temperature, the light yield of our acrylic sample relative to the TPB sample is 0.3 %, while it reaches 0.5 % at 4 K. The main fluorescence time constant of the acrylic is less than a few nanoseconds.

physics.ins-det↗

arXiv2021

Fluorescence of pyrene-doped polystyrene films from room temperature down to 4 K for wavelength-shifting applications

In liquid argon-based particle detectors, slow wavelength shifters (WLSs) could be used alongside the common, nanosecond scale, WLS tetraphenyl butadiene (TPB) for background mitigation purposes. At room temperature, pyrene has a moderate fluorescence light yield (LY) and a time constant of the order of hundreds of nanoseconds. In this work, four pyrene-doped polystyrene films with various purities and concentrations were characterized in terms of LY and decay time constants in a range of temperature between 4 K and 300 K under ultraviolet excitation. These films were found to have a LY between 35 and 50% of that of evaporated TPB. All light yields increase when cooling down, while the decays slow down. At room temperature, we observed that pyrene purity is strongly correlated with emission lifetime: highest obtainable purity samples were dominated by decays with emission time constants of $\sim$ 250-280 ns, and lower purity samples were dominated by an $\sim$ 80 ns component. One sample was investigated further to better understand the monomer and excimer emissions of pyrene. The excimer-over-monomer intensity ratio decreases when the temperature goes down, with the monomer emission dominating below $\sim$ 87 K.

physics.ins-det↗

arXiv2021

Development and characterization of a slow wavelength shifting coating for background rejection in liquid argon detectors

We describe a technique, applicable to liquid-argon-based dark matter detectors, allowing for discrimination of alpha-decays in detector regions with incomplete light collection from nuclear-recoil-like events. Nuclear recoils and alpha events preferentially excite the liquid argon (LAr) singlet state, which has a decay time of ~6 ns. The wavelength-shifter TPB, which is typically applied to the inside of the active detector volume to make the LAr scintillation photons visible, has a short re-emission time that preserves the LAr scintillation timing. We developed a wavelength-shifting polymeric film - pyrene-doped polystyrene - for the DEAP-3600 detector and describe the production method and characterization. At liquid argon temperature, the film's re-emission timing is dominated by a modified exponential decay with time constant of 279(14) ns and has a wavelength-shifting efficiency of 46.4(2.9) % relative to TPB, measured at room temperature. By coating the detector neck (a region outside the active volume where the scintillation light collection efficiency is low) with this film, the visible energy and the scintillation pulse shape of alpha events in the neck region are modified, and we predict that through pulse shape discrimination, the coating will afford a suppression factor of O($10^{5}$) against these events.

physics.ins-det↗

arXiv2019

The Hamburg Meteorite Fall: Fireball trajectory, orbit and dynamics

The Hamburg (H4) meteorite fell on January 17, 2018 at 01:08 UT approximately 10km North of Ann Arbor, Michigan. More than two dozen fragments totaling under one kilogram were recovered, primarily from frozen lake surfaces. The fireball initial velocity was 15.83 $\pm$ 0.05 km/s, based on four independent records showing the fireball above 50 km altitude. The radiant had a zenith angle of 66.1 $\pm$ 0.29 degs and an azimuth of 121.56 $\pm$ 1.2 degs. The resulting low inclination ($<$ 1 deg) Apollo-type orbit has a large aphelion distance and Tisserand value relative to Jupiter (Tj) of $\sim$ 3. Two major flares dominant the energy deposition profile, centred at 24.1 and 21.7 km altitude respectively under dynamic pressures of 5-7 MPa. Our preferred total energy for the Hamburg fireball is 2 to 7 T TNT (8.4 to 28 x 10$^9$ J), which corresponds to a likely initial mass in the range of 60 to 225 kg or diameter between 0.3 to 0.5 m. Based on the model of Granvik et al (2018), the meteorite originated in an escape route from the mid-outer asteroid belt. Hamburg is the 14th known H-chondrite with an instrumentally-derived pre-atmospheric orbit, half of which have small ($<$5 deg) inclinations making connection with (6) Hebe problematic. A definitive parent body consistent with all 14 known H-chondrite orbits remains elusive

astro-ph.EP↗

arXiv2015

A Model of Plasma Heating by Large-Scale Flow

In this work we study the process of energy dissipation triggered by a slow large scale motion of a magnetized conducting fluid. Our consideration is motivated by the problem of heating the solar corona, which is believed to be governed by fast reconnection events set off by the slow motion of magnetic field lines anchored in the photospheric plasma. To elucidate the physics governing the disruption of the imposed laminar motion and the energy transfer to small scales, we propose a simplified model where the large-scale motion of magnetic field lines is prescribed not at the footpoints but rather imposed volumetrically. As a result, the problem can be treated numerically with an efficient, highly-accurate spectral method, allowing us to use a resolution and statistical ensemble exceeding those of the previous work. We find that, even though the large-scale deformations are slow, they eventually lead to reconnection events that drive a turbulent state at smaller scales. The small-scale turbulence displays many of the universal features of field-guided MHD turbulence like a well developed inertial range spectrum. Based on these observations, we construct a phenomenological model that gives the scalings of the amplitude of the fluctuations and the energy dissipation rate as functions of the input parameters. We find a good agreement between the numerical results and the predictions of the model.

astro-ph.SR↗

arXiv2014

Comment on the numerical measurements of the magnetohydrodynamic turbulence spectrum by A. Beresnyak (Phys. Rev. Lett. 106 (2011) 075001; MNRAS 422 (2012) 3495; ApJ 784 (2014) L20)

The inertial-interval energy spectrum of strong magnetohydrodynamic (MHD) turbulence with a uniform background magnetic field was observed numerically to be close to $k^{-3/2}$ by a number of independent groups. A dissenting opinion has been voiced by Beresnyak, A. 2011, PRL, 106, 075001-. 2012, MNRAS, 422, 3495-. 2014, ApJ, 784, L20 that the spectral scaling is close to $k^{-5/3}$. The conclusions of these papers are however incorrect as they are based on numerical simulations that are drastically unresolved, so that the discrete numerical scheme does not approximate the physical solution at the scales where the measurements are performed. These results have been rebutted in our more detailed papers Perez, J. C., Mason, J., Boldyrev, S., & Cattaneo, F. 2012, PRX, 2, 041005-. 2014, ApJL, 793, L13; here, by popular demand, we present a brief and simple explanation of our major criticism of Beresnyak's work.

astro-ph.SR↗

arXiv2014

Scaling properties of small-scale fluctuations in magnetohydrodynamic turbulence

Magnetohydrodynamic (MHD) turbulence in the majority of natural systems, including the interstellar medium, the solar corona, and the solar wind, has Reynolds numbers far exceeding the Reynolds numbers achievable in numerical experiments. Much attention is therefore drawn to the universal scaling properties of small-scale fluctuations, which can be reliably measured in the simulations and then extrapolated to astrophysical scales. However, in contrast with hydrodynamic turbulence, where the universal structure of the inertial and dissipation intervals is described by the Kolmogorov self-similarity, the scaling for MHD turbulence cannot be established based solely on dimensional arguments due to the presence of an intrinsic velocity scale -- the Alfven velocity. In this Letter, we demonstrate that the Kolmogorov first self-similarity hypothesis cannot be formulated for MHD turbulence in the same way it is formulated for the hydrodynamic case. Besides profound consequences for the analytical consideration, this also imposes stringent conditions on numerical studies of MHD turbulence. In contrast with the hydrodynamic case, the discretization scale in numerical simulations of MHD turbulence should decrease faster than the dissipation scale, in order for the simulations to remain resolved as the Reynolds number increases.

astro-ph.SR↗

arXiv2009

Silencing noisy 2DEG wafers

Telegraphic noise is one of the most significant problems that arises when making sensitive measurements with lateral electrostatic devices. In this paper we demonstrate that a wafer which had only produced devices with significant telegraph noise problems can be made to produce 'quiet' devices if a thin insulator layer is placed between the gates and the GaAs/AlGaAs heterostructure. A slow drift in the resulting devices is attributed to the trapping of charges within the specific insulator used. This charge can be manipulated, leading to strategies for stabilizing the device.

cond-mat.mes-hall↗

arXiv2008

The effects of flux transport on interface dynamos

The operation of an interface dynamo (as has been suggested for the Sun and other stars with convective envelopes) relies crucially upon the effective transport of magnetic flux between two spatially disjoint generation regions. In the simplest models communication between the two regions is achieved solely by diffusion. Here we incorporate a highly simplified anisotropic transport mechanism in order to model the net effect of flux conveyance by magnetic pumping and by magnetic buoyancy. We investigate the influence of this mechanism on the efficiency of kinematic dynamo action. It is found that the effect of flux transport on the efficiency of the dynamo is dependent upon the spatial profile of the transport. Typically, transport hinders the onset of dynamo action and increases the frequency of the dynamo waves. However, in certain cases there exists a preferred magnitude of transport for which dynamo action is most efficient. Furthermore, we demonstrate the importance of the imposition of boundary conditions in drawing conclusions on the role of transport.

astro-ph↗