We report on a search for weakly interacting massive particles (WIMPs) using 278.8 days of data collected with the XENON1T experiment at LNGS. XENON1T utilizes a liquid xenon time projection chamber ...with a fiducial mass of (1.30±0.01) ton, resulting in a 1.0 ton yr exposure. The energy region of interest, 1.4,10.6 keV_{ee} (4.9,40.9 keV_{nr}), exhibits an ultralow electron recoil background rate of 82_{-3}^{+5}(syst)±3(stat) events/(ton yr keV_{ee}). No significant excess over background is found, and a profile likelihood analysis parametrized in spatial and energy dimensions excludes new parameter space for the WIMP-nucleon spin-independent elastic scatter cross section for WIMP masses above 6 GeV/c^{2}, with a minimum of 4.1×10^{-47} cm^{2} at 30 GeV/c^{2} and a 90% confidence level.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
Direct dark matter detection focuses on elastic scattering of dark matter particles off nuclei. In this study, we explore inelastic scattering where the nucleus is excited to a low-lying state of ...10-100 keV, with subsequent prompt deexcitation. We calculate the inelastic structure factors for the odd-mass xenon isotopes based on state-of-the-art shell-model calculations and chiral effective field theory for the interaction of weakly interacting massive particles with nucleons. For these cases, we find that the inelastic channel is comparable to or can dominate the elastic channel for momentum transfers around 150 MeV. We calculate the inelastic recoil spectra in the standard halo model, compare these to the elastic case, and discuss the expected signatures in a xenon detector, along with implications for existing and future experiments. The combined information from elastic and inelastic scattering will allow for the determination of the dominant interaction channel within one experiment. In addition, the two channels probe different regions of the dark matter velocity distribution and can provide insight into the dark halo structure. The allowed recoil energy domain and the recoil energy at which the integrated inelastic rates start to dominate the elastic channel depend on the mass of the dark matter particle, thus providing a potential handle to constrain its mass.
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We report on a search for nuclear recoil signals from solar B-8 neutrinos elastically scattering off xenon nuclei in XENON1T data, lowering the energy threshold from 2.6 to 1.6 keV. We develop a ...variety of novel techniques to limit the resulting increase in backgrounds near the threshold. No significant B-8 neutrinolike excess is found in an exposure of 0.6 t x y. For the first time, we use the nondetection of solar neutrinos to constrain the light yield from 1-2 keV nuclear recoils in liquid xenon, as well as nonstandard neutrino-quark interactions. Finally, we improve upon world-leading constraints on dark matter-nucleus interactions for dark matter masses between 3 and 11 GeV c(-2) by as much as an order of magnitude.
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The Ecological Society of America has evaluated current U.S. national policies and practices on biological invasions in light of current scientific knowledge. Invasions by harmful nonnative species ...are increasing in number and area affected; the damages to ecosystems, economic activity, and human welfare are accumulating. Without improved strategies based on recent scientific advances and increased investments to counter invasions, harm from invasive species is likely to accelerate. Federal leadership, with the cooperation of state and local governments, is required to increase the effectiveness of prevention of invasions, detect and respond quickly to new potentially harmful invasions, control and slow the spread of existing invasions, and provide a national center to ensure that these efforts are coordinated and cost effective. Specifically, the Ecological Society of America recommends that the federal government take the following six actions: (1) Use new information and practices to better manage commercial and other pathways to reduce the transport and release of potentially harmful species; (2) Adopt more quantitative procedures for risk analysis and apply them to every species proposed for importation into the country; (3) Use new cost-effective diagnostic technologies to increase active surveillance and sharing of information about invasive species so that responses to new invasions can be more rapid and effective; (4) Create new legal authority and provide emergency funding to support rapid responses to emerging invasions; (5) Provide funding and incentives for cost-effective programs to slow the spread of existing invasive species in order to protect still uninvaded ecosystems, social and industrial infrastructure, and human welfare; and (6) Establish a National Center for Invasive Species Management (under the existing National Invasive Species Council) to coordinate and lead improvements in federal, state, and international policies on invasive species. Recent scientific and technical advances provide a sound basis for more cost-effective national responses to invasive species. Greater investments in improved technology and management practices would be more than repaid by reduced damages from current and future invasive species. The Ecological Society of America is committed to assist all levels of government and provide scientific advice to improve all aspects of invasive-species management.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
The majority of agricultural and environmental weeds in Australia have originated from ornamental horticulture. Botanic gardens require a simple yet robust method for rapidly screening the relative ...weed risk of taxa in their collections. A ten question, multiple choice, additive weed risk assessment system was developed for application to taxa growing in gardens. The major city botanic gardens in Melbourne, Hobart and Perth used the system to score 100 taxa. Separately, a national survey and a literature review of the same 100 taxa were undertaken to obtain two independent datasets for assessing their level of weediness. Testing of the system showed that it has good discriminatory power and cut-off scores were chosen that have about 80% accuracy for both low weed risk and high weed risk species. There was poorer accuracy to distinguish medium weed risk species. The system has wider potential application for the nursery and garden industry as a tool to help reduce the number of high weed risk ornamental species in cultivation.
For the first time, a small dual-phase (liquid/gas) xenon time projection chamber was equipped with a top array of silicon photomultipliers for light and charge readout. Here we describe the ...instrument in detail, as well as the data processing and the event position reconstruction algorithms. We obtain a spatial resolution of Formula omitted in the horizontal plane. To characterise the detector performance, we show calibration data with internal Formula omitted and Formula omitted sources, and we detail the production of the latter as well as its introduction into the system. We finally compare the observed light and charge yields down to electronic recoil energies of Formula omitted to predictions based on NEST v2.0.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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