We report the first measurement of coherent elastic neutrino-nucleus scattering (CEvNS) on argon using a liquid argon detector at the Oak Ridge National Laboratory Spallation Neutron Source. Two ...independent analyses prefer CEvNS over the background-only null hypothesis with greater than 3σ significance. The measured cross section, averaged over the incident neutrino flux, is (2.2±0.7)×10^{-39} cm^{2}-consistent with the standard model prediction. The neutron-number dependence of this result, together with that from our previous measurement on CsI, confirms the existence of the CEvNS process and provides improved constraints on nonstandard neutrino interactions.
The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest of all low-energy neutrino couplings. This ...mode of interaction offers new opportunities to study neutrino properties and leads to a miniaturization of detector size, with potential technological applications. We observed this process at a 6.7σ̃ confidence level, using a low-background, 14.6-kilogram CsINa scintillator exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the standard model for this process, were observed in high signal-to-background conditions. Improved constraints on nonstandard neutrino interactions with quarks are derived from this initial data set.
This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of ^{235}U at the High Flux Isotope Reactor. PROSPECT, the Precision Reactor ...Oscillation and Spectrum Experiment, consists of a segmented 4 ton ^{6}Li-doped liquid scintillator detector covering a baseline range of 7-9 m from the reactor and operating under less than 1 m water equivalent overburden. Data collected during 33 live days of reactor operation at a nominal power of 85 MW yield a detection of 25 461±283 (stat) inverse beta decays. Observation of reactor antineutrinos can be achieved in PROSPECT at 5σ statistical significance within 2 h of on-surface reactor-on data taking. A reactor model independent analysis of the inverse beta decay prompt energy spectrum as a function of baseline constrains significant portions of the previously allowed sterile neutrino oscillation parameter space at 95% confidence level and disfavors the best fit of the reactor antineutrino anomaly at 2.2σ confidence level.
•Growth-climate relationships were analysed in black pine (ssp. laricio).•Drought effects on stem radial growth were studied in representative populations.•Positive impacts of precipitation in ...spring/summer, but negative in winter, were found.•Corsican populations were more sensitive to drought than populations in southern Italy.•Older trees were more resistant to drought events than younger trees.
The increased frequency and severity of drought events due to climate warming is negatively affecting tree radial growth, particularly in drought-prone regions, such as, e.g., the Mediterranean. In this climate change hotspot, populations of the same tree species may show different growth responses to climate, due to the great variety of microclimates and environments that characterise this biogeographic region. In this study, we analysed growth-climate relationships and growth responses to drought events (i.e., resistance, recovery, and resilience) in 13 forest stands of black pine (Pinus nigra Arnold), encompassing the whole and peculiar distribution range of the ssp. laricio (Calabria, Sicily, Sardinia, and Corsica). Analysis focussed on the 1981–2010 period, which is commonly covered at all sites. Stem radial growth of trees increased under a positive spring/summer water balance. However, abundant winter precipitation had a negative impact on stem radial growth. Populations in Corsica were more sensitive to drought, showing lower resistance and resilience than those in Sicily and Sardinia. Older trees were more resistant to drought events than younger trees. Our results highlight that population-specific responses to drought events are mainly explained by tree age and local environment, suggesting geographically related patterns in tree growth and forest productivity correspond to different populations. Intraspecific variability in sensitivity to drought events should be included in species distribution models to predict the range of forest productivity responses to climate change.
Members of the hominins - namely the so-called 'australopiths' and the species of the genus Homo - are known to possess short and deep mandibles and relatively small incisors and canines. It is ...commonly assumed that this suite of traits evolved in early members of the clade in response to changing environmental conditions and increased consumption of though food items. With the emergence of Homo, the functional meaning of mandible shape variation is thought to have been weakened by technological advancements and (later) by the control over fire. In contrast to this expectation, we found that mandible shape evolution in hominins is exceptionally rapid as compared to any other primate clade, and that the direction and rate of shape change (from the ape ancestor) are no different between the australopiths and Homo. We deem several factors including the loss of honing complex, canine reduction, and the acquisition of different diets may have concurred in producing such surprisingly high evolutionary rates. This study reveals the evolution of mandibular shape in hominins has strong morpho-functional and ecological significance attached.
Recognizing evolutionary trends in phenotypic means and rates requires the application of phylogenetic comparative methods (PCMs). Most PCMs are unsuited to make full use of fossil information, which ...is a drawback, given the inclusion of such data improves, and in some cases even corrects, the proper understanding of trait evolution. Here we present a new computer application, written in R, that allows the simultaneous computation of temporal trends in phenotypic mean and evolutionary rate along a phylogeny, and to contrast such patterns among different clades within the tree. By using simulation experiments, we show the new implementation, names search.trend is as powerful as existing PCM tools in discerning macroevolutionary patterns in phenotypic means and rates, but differently from any other PCM allows comparing individual clades to each other, and provides rich information about trait evolution for all lineages in the tree.
The COHERENT Collaboration searched for scalar dark matter particles produced at the Spallation Neutron Source with masses between 1 and 220 MeV/c^{2} using a CsINa scintillation detector sensitive ...to nuclear recoils above 9 keV_{nr}. No evidence for dark matter is found and we thus place limits on allowed parameter space. With this low-threshold detector, we are sensitive to coherent elastic scattering between dark matter and nuclei. The cross section for this process is orders of magnitude higher than for other processes historically used for accelerator-based direct-detection searches so that our small, 14.6 kg detector significantly improves on past constraints. At peak sensitivity, we reject the flux consistent with the cosmologically observed dark-matter concentration for all coupling constants α_{D}<0.64, assuming a scalar dark-matter particle. We also calculate the sensitivity of future COHERENT detectors to dark-matter signals which will ambitiously test multiple dark-matter spin scenarios.
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