Readout strategies for directional dark matter detection beyond the neutrino background

The search for weakly interacting massive particles (WIMPs) by direct detection faces an en- croaching background due to coherent neutrino-nucleus scattering. As the sensitivity of these ex- periments improves, the question of how to best distinguish a dark matter signal from neutrinos will become increasingly important. A proposed method of overcoming this so-called “neutrino floor” is to utilize the directional signature that both neutrino and dark matter induced recoils possess. We show that directional experiments can indeed probe WIMP-nucleon cross-sections below the neutrino floor with little loss in sensitivity due to the neutrino background. In particular we find at low WIMP masses (around 6 GeV) the discovery limits for directional detectors penetrate be- low the non-directional limit by several orders of magnitude. For high WIMP masses (around 100 GeV), the non-directional limit is overcome by a factor of a few. Furthermore we show that even for directional detectors which can only measure 1- or 2-dimensional projections of the 3-dimensional recoil track, the discovery potential is only reduced by a factor of 3 at most. We also demonstrate that while the experimental limitations of directional detectors, such as sense recognition and finite angular resolution, have a detrimental effect on the discovery limits, it is still possible to overcome the ultimate neutrino background faced by non-directional detectors

Pathogenicity of Phaeoacremonium aleophilum and Phaeomoniella chlamydospora on Grape Berries in California

Injured and non-injured grape berries were inoculated with spore suspension of Phaeomoniella chlamydospora or Phaeoacremonium aleophilum under field (intact berries) and laboratory (detached berries) conditions. In one test, berries were injured by pricking the skin with a syringe needle to a depth of approximately 1.5 mm. Brown to purple lesions appeared 5 to 7 days after inoculation in both the injured intact and detached berries. Lesions on these berries were larger when inoculated earlier in the season indicating that young, immature berries are more susceptible to infection than mature berries. In another test, berries were injured by rubbing the skin with carborundum dust using a cotton-tipped applicator. Esca-like lesions developed in 4 to 5 days after inoculation of detached but not intact berries. Occasional infection of non-injured berries occurred which appeared as small dots to pin-head size lesions around the lenticels. Scanning electron microscopy observations of these lesions showed abundant hyphal growth on the surface with apparent penetration through lenticels; however, fungal structures were not detected with certainty beneath the lenticels or intact cuticle. In both tests, the fungi were re-isolated from the advancing margin of the lesions

On the accuracy and precision of cardiac magnetic resonance T2 mapping: A high-resolution radial study using adiabatic T2 preparation at 3 T.

The goal of this study was to characterize the accuracy and precision of cardiac T2 mapping as a function of different factors including low signal-to-noise ratio (SNR), imaging in systole, and off-resonance frequencies. Bloch equation and Monte Carlo simulations were used to determine the influence of SNR and the choice of T2 preparation echo time (TET2prep ) increments on the accuracy and precision of high-resolution radial cardiac T2 mapping at 3.0 T. Healthy volunteers were scanned to establish the difference in precision and inter- and intraobserver variability between T2 mapping in diastole and systole, as well as the effect of SNR and off-resonance frequencies on the accuracy of T2 maps. The simulations demonstrated that a TET2prep increment of ∼0.75 times the T2 value of interest optimally increases the precision of the T2 fit. Systolic T2 maps were found to have a higher precision (P = 0.002), but similar inter- and intraobserver variability compared with diastolic T2 maps, whereas off-resonance frequencies beyond ± 100 Hz cause a significant decrease in both accuracy and precision (P < 0.05). This evaluation of the accuracy and precision of cardiac T2 mapping characterizes the major vulnerabilities of the technique and will help guide protocol definition of studies that include T2 mapping. Magn Reson Med 77:159-169, 2017. © 2016 Wiley Periodicals, Inc

Demonstration of surface electron rejection with interleaved germanium detectors for dark matter searches

The SuperCDMS experiment in the Soudan Underground Laboratory searches for dark matter with a 9-kg array of cryogenic germanium detectors. Symmetric sensors on opposite sides measure both charge and phonons from each particle interaction, providing excellent discrimination between electron and nuclear recoils, and between surface and interior events. Surface event rejection capabilities were tested with two 210 Pb sources producing ∼130 beta decays/hr. In ∼800 live hours, no events leaked into the 8–115 keV signal region, giving upper limit leakage fraction 1.7 × 10−5 at 90% C.L., corresponding to < 0.6 surface event background in the future 200-kg SuperCDMS SNOLAB experiment

Differential Susceptibility of Three Grapevine Cultivars to <em>Phaeomoniella chlamydospora</em> in California

One-year-old wood of grapevine cv. Thompson Seedless, Grenache, and Cabernet Sauvignon were pruned and the pruning wound immediately inoculated with a spore suspension (approximately 1 106 spores ml-1 of water) of Phaeomoniella chlamydospora or Phaeoacremonium aleophilum. Based on the incidence of esca 3 years after inoculation, Thompson Seedless was rated as the most susceptible of the 3 cultivars. The results are consistent with the observed incidence of naturally-occurring esca in California vineyards on these three cultivars

Epidemiology of SARS-CoV-2 Antibodies Among Firefighters/paramedics of a US Fire Department: A Cross-sectional Study

Objectives: We estimate the point seroprevalence of SARS-CoV-2 antibodies in the frontline firefighter/paramedic workforce of a South Florida fire department located in the epicentre of a State outbreak. Methods: A cross-sectional study design was used to estimate the point seroprevalence of SARS-CoV-2 antibodies using a rapid immunoglobulin (Ig)M-IgG combined point-of-care lateral flow immunoassay among frontline firefighters/paramedics collected over a 2-day period, 16-17 April 2020. Fire department personnel were emailed a survey link assessing COVID-19 symptoms and work exposures the day prior to the scheduled drive-through antibody testing at a designated fire station. Off-duty and on-duty firefighter/paramedic personnel drove through the fire station/training facility in their personal vehicles or on-duty engine/rescue trucks for SARS-CoV-2 antibody testing. Results: Among the 203 firefighters/paramedics that make up the fire department workforce, 18 firefighters/paramedics (8.9%) tested positive for SARS-CoV-2 antibodies, of which 8 firefighters/paramedics (3.9%) were IgG positive only, 8 (3.9%) were IgM positive only and 2 (0.1%) were IgG/IgM positive. The positive predictive value (PPV) of the serological test is estimated to be 33.2% and the negative predictive value is 99.3%. The average number of COVID-19 case contacts (ie, within 6 feet of an infected person (laboratory-confirmed or probable COVID-19 patient) for ≥15 min) experienced by firefighters/paramedics was higher for those with positive serology compared with those with negative (13.3 cases vs 7.31 cases; p=0.022). None of the antibody positive firefighters/paramedics reported receipt of the annual influenza vaccine compared with firefighters/paramedics who tested negative for SARS-CoV-2 antibodies (0.0% vs 21.0%; p=0.027). Conclusion: Rapid SARS-CoV-2 IgM-IgG antibody testing documented early-stage and late-stage infection in a firefighter workforce providing insight to a broader medical surveillance project on return to work for firefighters/paramedics. Given the relatively low PPV of the serological test used in this study back in April 2020, caution should be used in interpreting test results

Unfolding Neutron Spectrum with Markov Chain Monte Carlo at MIT Research Reactor with He-3 Neutral Current Detectors

International audienceThe Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CEνNS) using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2 × 1018 ν/second in its core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped Bonner cylinders around a 32He thermal neutron detector, whose data was then unfolded via a Markov Chain Monte Carlo (MCMC) to produce a neutron energy spectrum across several orders of magnitude. We discuss the resulting spectrum and its implications for deploying Ricochet at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup