Searcharxiv⌕ Search

arXiv subjects

M. Askins

Publications and source records attributed to M. Askins.

29 records · Page 2Linked to original sources
arXiv2020

Measurement of Muon-induced High-energy Neutrons from Rock in an Underground Gd-doped Water Detector

We present a measurement of the rate of correlated neutron captures in the WATCHBOY detector, deployed at a depth of approximately 390 meters water equivalent (m.w.e.) in the Kimballton Underground Research Facility (KURF). WATCHBOY consists of a cylindrical 2 ton water target doped with 0.1% gadolinium, surrounded by a 40 ton undoped water hermetic shield. We present a comparison of our results with the expected rate of correlated neutron captures arising from high-energy neutrons incident on the outside of the WATCHBOY shield, predicted by a hybrid FLUKA/GEANT4-based simulation. The incident neutron energy distribution used in the simulation was measured by a fast neutron spectrometer, the 1.8-ton Multiplicity and Recoil Spectrometer (MARS) detector, at the same depth. We find that the measured detection rate of two correlated neutrons is consistent with that predicted by simulation. The result lends additional confidence in the detection technique used by MARS, and therefore in the MARS spectra as measured at three different depths. Confirmation of the fast neutron flux and spectrum is important as it helps validate the scaling models used to predict the fast neutron fluxes at different overburdens.

physics.ins-det↗
arXiv2020

Measurement of neutron-proton capture in the SNO+ water phase

The SNO+ experiment collected data as a low-threshold water Cherenkov detector from September 2017 to July 2019. Measurements of the 2.2-MeV $γ$ produced by neutron capture on hydrogen have been made using an Am-Be calibration source, for which a large fraction of emitted neutrons are produced simultaneously with a 4.4-MeV $γ$. Analysis of the delayed coincidence between the 4.4-MeV $γ$ and the 2.2-MeV capture $γ$ revealed a neutron detection efficiency that is centered around 50% and varies at the level of 1% across the inner region of the detector, which to our knowledge is the highest efficiency achieved among pure water Cherenkov detectors. In addition, the neutron capture time constant was measured and converted to a thermal neutron-proton capture cross section of $336.3^{+1.2}_{-1.5}$ mb.

physics.ins-det↗
arXiv2019

Directionally Accelerated Detection of an Unknown Second Reactor with Antineutrinos for Mid-Field Nonproliferation Monitoring

When monitoring a reactor site for nuclear nonproliferation purposes, the presence of an unknown or hidden nuclear reactor could be obscured by the activities of a known reactor of much greater power nearby. Thus when monitoring reactor activities by the observation of antineutrino emissions, one must discriminate known background reactor fluxes from possible unknown reactor signals under investigation. To quantify this discrimination, we find the confidence to reject the (null) hypothesis of a single proximal reactor, by exploiting directional antineutrino signals in the presence of a second, unknown reactor. In particular, we simulate the inverse beta decay (IBD) response of a detector filled with a 1 kT fiducial mass of Gadolinium-doped liquid scintillator in mineral oil. We base the detector geometry on that of WATCHMAN, an upcoming antineutrino monitoring experiment soon to be deployed at the Boulby mine in the United Kingdom whose design and deployment will be detailed in a forthcoming white paper. From this simulation, we construct an analytical model of the IBD event distribution for the case of one $4\mathrm{\ GWt}\pm2\%$ reactor 25 km away from the detector site, and for an additional, unknown, 35 MWt reactor 3 to 5 km away. The effects of natural-background rejection cuts are approximated. Applying the model, we predict $3σ$ confidence to detect the presence of an unknown reactor within five weeks, at standoffs of 3 km or nearer. For more distant unknown reactors, the $3σ$ detection time increases significantly. However, the relative significance of directional sensitivity also increases, providing up to an eight week speedup to detect an unknown reactor at 5 km away. Therefore, directionally sensitive antineutrino monitoring can accelerate the mid-field detection of unknown reactors whose operation might otherwise be masked by more powerful reactors in the vicinity.

physics.ins-det↗
arXiv2019

Measurement of the $^8$B Solar Neutrino Flux in SNO+ with Very Low Backgrounds

A measurement of the $^8$B solar neutrino flux has been made using a 69.2 kt-day dataset acquired with the SNO+ detector during its water commissioning phase. At energies above 6 MeV the dataset is an extremely pure sample of solar neutrino elastic scattering events, owing primarily to the detector's deep location, allowing an accurate measurement with relatively little exposure. In that energy region the best fit background rate is $0.25^{+0.09}_{-0.07}$ events/kt-day, significantly lower than the measured solar neutrino event rate in that energy range, which is $1.03^{+0.13}_{-0.12}$ events/kt-day. Also using data below this threshold, down to 5 MeV, fits of the solar neutrino event direction yielded an observed flux of $2.53^{+0.31}_{-0.28}$(stat.)$^{+0.13}_{-0.10}$(syst.)$\times10^6$ cm$^{-2}$s$^{-1}$, assuming no neutrino oscillations. This rate is consistent with matter enhanced neutrino oscillations and measurements from other experiments.

hep-ex↗
arXiv2018

Search for invisible modes of nucleon decay in water with the SNO+ detector

This paper reports results from a search for nucleon decay through 'invisible' modes, where no visible energy is directly deposited during the decay itself, during the initial water phase of SNO+. However, such decays within the oxygen nucleus would produce an excited daughter that would subsequently de-excite, often emitting detectable gamma rays. A search for such gamma rays yields limits of $2.5 \times 10^{29}$ y at 90% Bayesian credibility level (with a prior uniform in rate) for the partial lifetime of the neutron, and $3.6 \times 10^{29}$ y for the partial lifetime of the proton, the latter a 70% improvement on the previous limit from SNO. We also present partial lifetime limits for invisible dinucleon modes of $1.3\times 10^{28}$ y for $nn$, $2.6\times 10^{28}$ y for $pn$ and $4.7\times 10^{28}$ y for $pp$, an improvement over existing limits by close to three orders of magnitude for the latter two.

hep-ex↗
arXiv2016

A search for cosmogenic production of $β$-neutron emitting radionuclides in water

Here we present the first results of WATCHBOY, a water Cherenkov detector designed to measure the yield of $β$-neutron emitting radionuclides produced by cosmic ray muons in water. In addition to the $β$-neutron measurement, we also provide a first look at isolating single-$β$ producing radionuclides following muon-induced hadronic showers as a check of the detection capabilities of WATCHBOY. The data taken over $207$ live days indicates a $^{9}$Li production yield upper limit of $1.9\times10^{-7}μ^{-1}g^{-1}\mathrm{cm}^2$ at $\sim400$ meters water equivalent (m.w.e.) overburden at the $90\%$ confidence level. In this work the $^{9}$Li signal in WATCHBOY was used as a proxy for the combined search for $^{9}$Li and $^{8}$He production. This result will provide a constraint on estimates of antineutrino-like backgrounds in future water-based antineutrino detectors.

nucl-ex↗
arXiv2016

Current Status and Future Prospects of the SNO+ Experiment

SNO+ is a large liquid scintillator-based experiment located 2km underground at SNOLAB, Sudbury, Canada. It reuses the Sudbury Neutrino Observatory detector, consisting of a 12m diameter acrylic vessel which will be filled with about 780 tonnes of ultra-pure liquid scintillator. Designed as a multipurpose neutrino experiment, the primary goal of SNO+ is a search for the neutrinoless double-beta decay (0$νββ$) of 130Te. In Phase I, the detector will be loaded with 0.3% natural tellurium, corresponding to nearly 800 kg of 130Te, with an expected effective Majorana neutrino mass sensitivity in the region of 55-133 meV, just above the inverted mass hierarchy. Recently, the possibility of deploying up to ten times more natural tellurium has been investigated, which would enable SNO+ to achieve sensitivity deep into the parameter space for the inverted neutrino mass hierarchy in the future. Additionally, SNO+ aims to measure reactor antineutrino oscillations, low-energy solar neutrinos, and geoneutrinos, to be sensitive to supernova neutrinos, and to search for exotic physics. A first phase with the detector filled with water will begin soon, with the scintillator phase expected to start after a few months of water data taking. The 0$νββ$ Phase I is foreseen for 2017.

physics.ins-det↗
arXiv2015

Physics Potential of a Long Baseline Neutrino Oscillation Experiment Using J-PARC Neutrino Beam and Hyper-Kamiokande

Hyper-Kamiokande will be a next generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of Hyper-Kamiokande is the study of $CP$ asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams. In this paper, the physics potential of a long baseline neutrino experiment using the Hyper-Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis uses the framework and systematic uncertainties derived from the ongoing T2K experiment. With a total exposure of 7.5 MW $\times$ 10$^7$ sec integrated proton beam power (corresponding to $1.56\times10^{22}$ protons on target with a 30 GeV proton beam) to a $2.5$-degree off-axis neutrino beam, it is expected that the leptonic $CP$ phase $δ_{CP}$ can be determined to better than 19 degrees for all possible values of $δ_{CP}$, and $CP$ violation can be established with a statistical significance of more than $3\,σ$ ($5\,σ$) for $76\%$ ($58\%$) of the $δ_{CP}$ parameter space. Using both $ν_e$ appearance and $ν_μ$ disappearance data, the expected 1$σ$ uncertainty of $\sin^2θ_{23}$ is 0.015(0.006) for $\sin^2θ_{23}=0.5(0.45)$.

hep-ex↗
arXiv2015

The Physics and Nuclear Nonproliferation Goals of WATCHMAN: A WAter CHerenkov Monitor for ANtineutrinos

This article describes the physics and nonproliferation goals of WATCHMAN, the WAter Cherenkov Monitor for ANtineutrinos. The baseline WATCHMAN design is a kiloton scale gadolinium-doped (Gd) light water Cherenkov detector, placed 13 kilometers from a civil nuclear reactor in the United States. In its first deployment phase, WATCHMAN will be used to remotely detect a change in the operational status of the reactor, providing a first- ever demonstration of the potential of large Gd-doped water detectors for remote reactor monitoring for future international nuclear nonproliferation applications. During its first phase, the detector will provide a critical large-scale test of the ability to tag neutrons and thus distinguish low energy electron neutrinos and antineutrinos. This would make WATCHMAN the only detector capable of providing both direction and flavor identification of supernova neutrinos. It would also be the third largest supernova detector, and the largest underground in the western hemisphere. In a follow-on phase incorporating the IsoDAR neutrino beam, the detector would have world-class sensitivity to sterile neutrino signatures and to non-standard electroweak interactions (NSI). WATCHMAN will also be a major, U.S. based integration platform for a host of technologies relevant for the Long-Baseline Neutrino Facility (LBNF) and other future large detectors. This white paper describes the WATCHMAN conceptual design,and presents the results of detailed simulations of sensitivity for the project's nonproliferation and physics goals. It also describes the advanced technologies to be used in WATCHMAN, including high quantum efficiency photomultipliers, Water-Based Liquid Scintillator (WbLS), picosecond light sensors such as the Large Area Picosecond Photo Detector (LAPPD), and advanced pattern recognition and particle identification methods.

physics.ins-det↗
arXiv2015

A Long Baseline Neutrino Oscillation Experiment Using J-PARC Neutrino Beam and Hyper-Kamiokande

Hyper-Kamiokande will be a next generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of Hyper-Kamiokande is the study of $CP$ asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams. In this document, the physics potential of a long baseline neutrino experiment using the Hyper-Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis has been updated from the previous Letter of Intent [K. Abe et al., arXiv:1109.3262 [hep-ex]], based on the experience gained from the ongoing T2K experiment. With a total exposure of 7.5 MW $\times$ 10$^7$ sec integrated proton beam power (corresponding to $1.56\times10^{22}$ protons on target with a 30 GeV proton beam) to a $2.5$-degree off-axis neutrino beam produced by the J-PARC proton synchrotron, it is expected that the $CP$ phase $δ_{CP}$ can be determined to better than 19 degrees for all possible values of $δ_{CP}$, and $CP$ violation can be established with a statistical significance of more than $3\,σ$ ($5\,σ$) for $76%$ ($58%$) of the $δ_{CP}$ parameter space.

physics.ins-det↗