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DEAP-3600 is a liquid-argon scintillation detector looking for dark matter. Scintillation events in the liquid argon (LAr) are registered by 255 photomultiplier tubes (PMTs), and pulseshape discrimination (PSD) is used to suppress electromagnetic background events. The excellent PSD performance of LAr makes it a viable target for dark matter searches, and the LAr scintillation pulseshape discussed here is the basis of PSD. The observed pulseshape is a combination of LAr scintillation physics with detector effects. We present a model for the pulseshape of electromagnetic background events in the energy region of interest for dark matter searches. The model is composed of (a) LAr scintillation physics, including the so-called intermediate component, (b) the time response of the TPB wavelength shifter, including delayed TPB emission at O (ms) time-scales, and c) PMT response. TPB is the wavelength shifter of choice in most LAr detectors. We find that approximately 10% of the intensity of the wavelength-shifted light is in a long-lived state of TPB. This causes light from an event to spill into subsequent events to an extent not usually accounted for in the design and data analysis of LAr-based detectors.

The specific activity of the$$\\beta $$β decay of$$^{39}$$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 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of$$^{39}$$39 Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001$$_\\textrm{stat}$$stat ± 0.024$$_\\textrm{sys}$$sys ) Bq/kg$$_\\textrm{atmAr}$$atmAr , which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.

The specific activity of the β 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 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of 39 Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001 stat ± 0.024 sys ) Bq/kg atmAr , which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.

Abstract The specific activity of theβ β decay of³⁹39 Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of³⁹39 Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001_(\\textrm{stat}{}{})stat ± 0.024_(\\textrm{sys}{}{})sys ) Bq/kg_(\\textrm{atmAr}{}{})atmAr , which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.

An analysis of solar neutrino data from the fourth phase of Super-Kamiokande~(SK-IV) from October 2008 to May 2018 is performed and the results are presented. The observation time of the data set of SK-IV corresponds to \\(2970\\)~days and the total live time for all four phases is \\(5805\\)~days. For more precise solar neutrino measurements, several improvements are applied in this analysis: lowering the data acquisition threshold in May 2015, further reduction of the spallation background using neutron clustering events, precise energy reconstruction considering the time variation of the PMT gain. The observed number of solar neutrino events in \\(3.49\\)--\\(19.49\\) MeV electron kinetic energy region during SK-IV is \\(65,443^{+390}_{-388}\\,(\\mathrm{stat.})\\pm 925\\,(\\mathrm{syst.})\\) events. Corresponding \\(\\mathrm{^{8}B}\\) solar neutrino flux is \\((2.314 \\pm 0.014\\, \\rm{(stat.)} \\pm 0.040 \\, \\rm{(syst.)}) \\times 10^{6}~\\mathrm{cm^{-2}\\,s^{-1}}\\), assuming a pure electron-neutrino flavor component without neutrino oscillations. The flux combined with all SK phases up to SK-IV is \\((2.336 \\pm 0.011\\, \\rm{(stat.)} \\pm 0.043 \\, \\rm{(syst.)}) \\times 10^{6}~\\mathrm{cm^{-2}\\,s^{-1}}\\). Based on the neutrino oscillation analysis from all solar experiments, including the SK \\(5805\\)~days data set, the best-fit neutrino oscillation parameters are \\(\\rm{sin^{2} \\theta_{12,\\,solar}} = 0.306 \\pm 0.013 \\) and \\(\\Delta m^{2}_{21,\\,\\mathrm{solar}} = (6.10^{+ 0.95}_{-0.81}) \\times 10^{-5}~\\rm{eV}^{2}\\), with a deviation of about 1.5\\(\\sigma\\) from the \\(\\Delta m^{2}_{21}\\) parameter obtained by KamLAND. The best-fit neutrino oscillation parameters obtained from all solar experiments and KamLAND are \\(\\sin^{2} \\theta_{12,\\,\\mathrm{global}} = 0.307 \\pm 0.012 \\) and \\(\\Delta m^{2}_{21,\\,\\mathrm{global}} = (7.50^{+ 0.19}_{-0.18}) \\times 10^{-5}~\\rm{eV}^{2}\\).

We present the development of neutron-tagging techniques in Super-Kamiokande IV using a neural network analysis. The detection efficiency of neutron capture on hydrogen is estimated to be 26%, with a mis-tag rate of 0.016 per neutrino event. The uncertainty of the tagging efficiency is estimated to be 9.0%. Measurement of the tagging efficiency with data from an Americium-Beryllium calibration agrees with this value within 10%. The tagging procedure was performed on 3,244.4 days of SK-IV atmospheric neutrino data, identifying 18,091 neutrons in 26,473 neutrino events. The fitted neutron capture lifetime was measured as 218 \\pm 9 \\mu s.

The 1991 Persian Gulf War provided clear evidence of the continuing military power of the US. It sent over 500,000 troops to that war, a contingent that included the largest group of female personnel the US had ever sent to a military conflict. In the wake of their achievements, many advocates and scholars predicted that the number of women in the military would continue to increase, and that the range of their participation would also expand. This paper examines the role of cultural values and images as they affect women's military roles. It does so by applying Judith Hicks Stiehm's framework of the protector and the protected (traditionally male and female, respectively) to the symbolic meaning and practical experiences of the United States' first female Prisoner of War (POW) in the Gulf War, Melissa Rathbun-Nealy. A female POW presents one of the greatest challenges to society's perception of women's military competency and usefulness. Rathbun-Nealy's capture and imprisonment, the American government's reaction to it, and the media's coverage of these events, therefore reveal much about women's roles in the US military, both during and after the Gulf War. This analysis concludes that women's contributions to the Gulf War may have been exceptional, but that the post-war return to normalcy included a return to the gendered image of women as protected citizens.

We present a search for an excess of neutrino interactions due to dark matter in the form of Weakly Interacting Massive Particles (WIMPs) annihilating in the galactic center or halo based on the data set of Super-Kamiokande-I, -II, -III and -IV taken from 1996 to 2016. We model the neutrino flux, energy, and flavor distributions assuming WIMP self-annihilation is dominant to \\(\\nu \\overline{\\nu}\\), \\(\\mu^+\\mu^-\\), \\(b\\overline{b}\\), or \\(W^+W^-\\). The excess is in comparison to atmospheric neutrino interactions which are modeled in detail and fit to data. Limits on the self-annihilation cross section \\(\\langle \\sigma_{A} V \\rangle\\) are derived for WIMP masses in the range 1 GeV to 10 TeV, reaching as low as \\(9.6 \\times10^{-23}\\) cm\\(^3\\) s\\(^{-1}\\) for 5 GeV WIMPs in \\(b\\bar b\\) mode and \\(1.2 \\times10^{-24}\\) cm\\(^3\\) s\\(^{-1}\\) for 1 GeV WIMPs in \\(\\nu \\bar \\nu\\) mode. The obtained sensitivity of the Super-Kamiokande detector to WIMP masses below several tens of GeV is the best among similar indirect searches to date.

A search for proton decay into three charged leptons has been performed by using 0.37\\(\\,\\)Mton\\(\\cdot\\)years of data collected in Super-Kamiokande. All possible combinations of electrons, muons and their anti-particles consistent with charge conservation were considered as decay modes. No significant excess of events has been found over the background, and lower limits on the proton lifetime divided by the branching ratio have been obtained. The limits range between \\(9.2\\times10^{33}\\) to \\(3.4\\times10^{34}\\) years at 90\\(\\,\\)% confidence level, improving by more than an order of magnitude upon limits from previous experiments. A first limit has been set for the \\(p\\rightarrow\\mu^-e^+e^+\\) mode.

We report a search for astronomical neutrinos in the energy region from several GeV to TeV in the direction of the blazar TXS0506+056 using the Super-Kamiokande detector following the detection of a 100 TeV neutrino from the same location by the IceCube collaboration. Using Super-Kamiokande neutrino data across several data samples observed from April 1996 to February 2018 we have searched for both a total excess above known backgrounds across the entire period as well as localized excesses on smaller time scales in that interval. No significant excess nor significant variation in the observed event rate are found in the blazar direction. Upper limits are placed on the electron and muon neutrino fluxes at 90\\% confidence level as \\(6.03 \\times 10^{-7}\\) and \\(4.52 \\times 10^{-7}\\) to \\(9.26 \\times 10^{-10}\\) [\\({\\rm erg}/{\\rm cm}^2/{\\rm s}\\)], respectively.