181 research outputs found
Theia: an advanced optical neutrino detector
New developments in liquid scintillators, high-efficiency, fast photon detectors, and chromatic photon sorting have opened up the possibility for building a large-scale detector that can discriminate between Cherenkov and scintillation signals. Such a detector could reconstruct particle direction and species using Cherenkov light while also having the excellent energy resolution and low threshold of a scintillator detector. Situated deep underground, and utilizing new techniques in computing and reconstruction, this detector could achieve unprecedented levels of background rejection, enabling a rich physics program spanning topics in nuclear, high-energy, and astrophysics, and across a dynamic range from hundreds of keV to many GeV. The scientific program would include observations of low- and high-energy solar neutrinos, determination of neutrino mass ordering and measurement of the neutrino CP-violating phase ÎŽ, observations of diffuse supernova neutrinos and neutrinos from a supernova burst, sensitive searches for nucleon decay and, ultimately, a search for neutrinoless double beta decay, with sensitivity reaching the normal ordering regime of neutrino mass phase space. This paper describes Theia, a detector design that incorporates these new technologies in a practical and affordable way to accomplish the science goals described above
Search for astronomical neutrinos from blazar TXS 0506+056 in super-kamiokande
We report a search for astronomical neutrinos in the energy region from several GeV to TeV in the direction of the blazar TXS 0506+056 using the Super-Kamiokande detector following the detection of a 100 TeV neutrinos from the same location by the IceCube collaboration. Using Super-Kamiokande neutrino data across several data samples observed from 1996 April to 2018 February we have searched for both a total excess above known backgrounds across the entire period as well as localized excesses on smaller timescales 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 the 90% confidence level as 6.0 Ă 10â7 and 4.5 Ă 10â7â9.3 Ă 10â10 [erg cmâ2 sâ1], respectively
Evidence of antineutrinos from distant reactors using pure water at SNO
The SNO+ Collaboration reports the first evidence of reactor antineutrinos in a Cherenkov detector. The nearest nuclear reactors are located 240Â km away in Ontario, Canada. This analysis uses events with energies lower than in any previous analysis with a large water Cherenkov detector. Two analytical methods are used to distinguish reactor antineutrinos from background events in 190Â days of data and yield consistent evidence for antineutrinos with a combined significance of 3.5Ï
Measurement of neutron-proton capture in the SNO+ water phase
The SNO+ experiment collected data as a low-threshold water Cherenkov
detector from September 2017 to July 2019. Measurements of the 2.2-MeV
produced by neutron capture on hydrogen have been made using an Am-Be
calibration source, for which a large fraction of emitted neutrons are produced
simultaneously with a 4.4-MeV . Analysis of the delayed coincidence
between the 4.4-MeV and the 2.2-MeV capture revealed a
neutron detection efficiency that is centered around 50% and varies at the
level of 1% across the inner region of the detector, which to our knowledge is
the highest efficiency achieved among pure water Cherenkov detectors. In
addition, the neutron capture time constant was measured and converted to a
thermal neutron-proton capture cross section of mb
Improved search for invisible modes of nucleon decay in water with the SNO+ detector
This paper reports results from a search for single and multi-nucleon
disappearance from the O nucleus in water within the \snoplus{} detector
using all of the available data. These so-called "invisible" decays do not
directly deposit energy within the detector but are instead detected through
their subsequent nuclear de-excitation and gamma-ray emission. New limits are
given for the partial lifetimes:
years, years, years,
years, and years at 90\% Bayesian
credibility level (with a prior uniform in rate). All but the () results improve on existing limits by a factor of about 3.info:eu-repo/semantics/publishedVersio
Observation of Antineutrinos from Distant Reactors using Pure Water at SNO+
The SNO+ collaboration reports the first observation of reactor antineutrinos
in a Cherenkov detector. The nearest nuclear reactors are located 240 km away
in Ontario, Canada. This analysis used events with energies lower than in any
previous analysis with a large water Cherenkov detector. Two analytical methods
were used to distinguish reactor antineutrinos from background events in 190
days of data and yielded consistent observations of antineutrinos with a
combined significance of 3.5 .Comment: v2: add missing author, add link to supplemental materia
Evolutionary winners are ecological losers among oceanic island plants
Aim
Adaptive radiation, in which successful lineages proliferate by exploiting untapped niche space, provides a popular but potentially misleading characterization of evolution on oceanic islands. Here we analyse the respective roles of members of in situ diversified vs. non-diversified lineages in shaping the main ecosystems of an archipelago to explore the relationship between evolutionary and ecological âsuccessâ.
Location
Canary Islands.
Taxon
Vascular plants.
Methods
We quantified the abundance/rarity of the native flora according to the geographical range (number of islands where present and geographical extent of the range), habitat breadth (climatic niche) and local abundance (cover) using species distribution data based on 500 Ă 500 m grid cells and 2000 vegetation inventories located all over the archipelago.
Results
Species of diversified lineages have significantly smaller geographic ranges, narrower climatic niches and lower local abundances than those of non-diversified lineages. Species rarity increased with the degree of diversification. The diversified Canarian flora is mainly comprised by shrubs. At both archipelagic and island level, the four core ecosystems (Euphorbia scrub, thermophilous woodlands, laurel forest and pine forest) were dominated by non-diversified lineages species, with diversified lineages species providing <25% cover. Species of diversified lineages, although constituting 54% of the archipelagic native flora, were only abundant in two rare ecosystems: high mountain scrub and rock communities.
Main conclusions
Radiated species, endemic products of in situ speciation, are mostly rare in all three rarity axes and typically do not play an important role in structuring plant communities on the Canaries. The vegetation of the major ecosystem types is dominated by plants representing non-diversified lineages (species that derive from immigration and accumulation), while species of evolutionarily successful lineages are abundant only in marginal habitats and could, therefore, be considered ecological losers. Within this particular oceanic archipelago, and we posit within at least some others, evolutionary success in plants is accomplished predominantly at the margins.publishedVersio
Search for proton decay into three charged leptons in 0.37 megaton-years exposure of the Super-Kamiokande
A search for proton decay into three charged leptons has been performed by using 0.37 Mtonâ
years of data collected in Super-Kamiokande. All possible combinations of electrons, muons, and their antiparticles 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 9.2Ă10^33 and 3.4Ă10^34 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 pâÎŒ^âe^+e^+ mode
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