Measurements of atmospheric neutrinos and antineutrinos in the MINOS far detector

This paper reports measurements of atmospheric neutrino and antineutrino interactions in the MINOS Far Detector, based on 2553 live-days (37.9 kton-years) of data. A total of 2072 candidate events are observed. These are separated into 905 contained-vertex muons and 466 neutrino-induced rock-muons, both produced by charged-current v_µ and v¯_µ interactions, and 701 contained-vertex showers, composed mainly of charged-current v_e and v¯_e interactions and neutral-current interactions. The curvature of muon tracks in the magnetic field of the MINOS Far Detector is used to select separate samples of v_µ and v¯_µ events. The observed ration of v¯_µ to v_µ events is compared with the Monte Carlo (MC) simulation, giving a double ration of (R^(data)_(v¯/v))/(R^(MC)_(v¯/v)) = 1.03 ± 0.08(stat) ± 0.08(syst). The v_µ and v¯_µ data are separated into bins of L/E resolution, based on the reconstructed energy and direction of each event, and a maximum likelihood fit to the observed L/E distributions is used to determine the atmospheric neutrino oscillation parameters. This fit returns 90% confidence limits of |Δm^2| = (1.9 ± 0.4) x 10^(-3) eV^2 and sin^(2)2θ > 0.86. The fit is extended to incorporate separate v_µ and v¯_µ oscillation parameters, returning 90% confidence limits of |Δm^2|-|Δm¯^2| = 0.6^(2.4)_(-0.8) x 10^(-3) eV^2 on the difference between the squared-mass splittings for neutrinos and antineutrinos

First results from the DEAP-3600 dark matter search with argon at SNOLAB

This paper reports the first results of a direct dark matter search with the DEAP-3600 single-phase liquid argon (LAr) detector. The experiment was performed 2 km underground at SNOLAB (Sudbury, Canada) utilizing a large target mass, with the LAr target contained in a spherical acrylic vessel of 3600 kg capacity. The LAr is viewed by an array of PMTs, which would register scintillation light produced by rare nuclear recoil signals induced by dark matter particle scattering. An analysis of 4.44 live days (fiducial exposure of 9.87 tonne-days) of data taken with the nearly full detector during the initial filling phase demonstrates the detector performance and the best electronic recoil rejection using pulse-shape discrimination in argon, with leakage <1.2\times 10^{-7} (90% C.L.) between 16 and 33 keV$_{ee}$. No candidate signal events are observed, which results in the leading limit on WIMP-nucleon spin-independent cross section on argon, <1.2\times 10^{-44} cm$^2$ for a 100 GeV/c$^2$ WIMP mass (90% C.L.)

Indication of electron neutrino appearance from an accelerator-produced off-axis muon neutrino beam.

The T2K experiment observes indications of ν(μ) → ν(e) appearance in data accumulated with 1.43×10(20) protons on target. Six events pass all selection criteria at the far detector. In a three-flavor neutrino oscillation scenario with |Δm(23)(2)| = 2.4×10(-3)  eV(2), sin(2)2θ(23) = 1 and sin(2)2θ(13) = 0, the expected number of such events is 1.5±0.3(syst). Under this hypothesis, the probability to observe six or more candidate events is 7×10(-3), equivalent to 2.5σ significance. At 90% C.L., the data are consistent with 0.03(0.04) < sin(2)2θ(13) < 0.28(0.34) for δ(CP) = 0 and a normal (inverted) hierarchy