Strangeness in nuclear physics Gal, A.; Hungerford, E. V.; Millener, D. J.
Reviews of modern physics,
08/2016, Letnik:
88, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Extensions of nuclear physics to the strange sector are reviewed, covering data and models of Lambda and other hypernuclei, multistrange matter, and antikaon bound states and condensation. Past ...achievements are highlighted, present unresolved problems are discussed, and future directions are outlined.
The DarkSide-50 direct-detection dark matter experiment is a dual-phase argon time projection chamber operating at Laboratori Nazionali del Gran Sasso. This paper reports on the blind analysis of a ...(16 660±270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We find no events in the dark matter selection box and set a 90% C.L. upper limit on the dark matter–nucleon spin-independent cross section of 1.14×10−44 cm2 (3.78×10−44 cm2, 3.43×10−43 cm2) for a WIMP mass of 100 GeV/c2 (1 TeV/c2, 10 TeV/c2).
Neutrons produced by cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically such neutrons can dominate the background, ...as they are particularly difficult to shield and detect. Since actual data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. Thus validation of any simulation code is necessary to assure reliable results. This work compares in detail predictions of the FLUKA simulation code to existing data, and uses this code to report a simulation of cosmogenic backgrounds for typical detectors embedded in a water tank with liquid scintillator shielding.
This paper derives equations for the deflection of an anode wire in a proportional straw chamber under electrostatic forces due to misalignments of the wire, deformation of the straw tube surface, ...and gravity.
The EuroRotaNet surveillance network has conducted rotavirus genotype surveillance since 2007 in 16 European countries. Using epidemiological and microbiological data from 39,786 genotyped ...rotavirus-positive specimens collected between September 2007 and August 2013, we assessed genotype distribution and age distribution of rotavirus gastroenteritis (RVGE) cases in and out of peak season in 12 countries which were yet to implement routine rotavirus vaccination. In multinomial multivariate logistic regression, adjusting for year, country and age, the odds of infection caused by genotype-constellation 2 DS-1-like stains (adjusted multinomial odds ratio (aM-OR) = 1.25; 95% confidence interval (CI): 1.13-1.37; p < 0.001), mixed or untypable genotypes (aM-OR = 1.55; 95% CI: 1.40-1.72; p < 0.001) and less common genotypes (aM-OR = 2.11; 95% CI:1.78-2.51; p < 0.001) increased out of season relative to G1P8. Age varied significantly between seasons; the proportion of RVGE cases younger than 12 months in the United Kingdom increased from 34% in season to 39% out of season (aM-OR = 1.66; 95% CI: 1.20-2.30), and the proportion five years and older increased from 9% in season to 17% out of season (aM-OR = 2.53; 95% CI: 1.67-3.82). This study provides further understanding of the rotavirus ecology before vaccine introduction, which will help interpret epidemiological changes in countries introducing or expanding rotavirus vaccination programmes.
Precision measurements of solar neutrinos emitted by specific nuclear reaction chains in the Sun are of great interest for developing an improved understanding of star formation and evolution. Given ...the expected neutrino fluxes and known detection reactions, such measurements require detectors capable of collecting neutrino-electron scattering data in exposures on the order of 1 ktonne-yr, with good energy resolution and extremely low background. Two-phase liquid argon time projection chambers (LAr TPCs) are under development for direct Dark Matter WIMP searches, which possess very large sensitive mass, high scintillation light yield, good energy resolution, and good spatial resolution in all three cartesian directions. While enabling Dark Matter searches with sensitivity extending to the ''neutrino floor'' (given by the rate of nuclear recoil events from solar neutrino coherent scattering), such detectors could also enable precision measurements of solar neutrino fluxes using the neutrino-electron elastic scattering events. Modeling results are presented for the cosmogenic and radiogenic backgrounds affecting solar neutrino detection in a 300 tonne (100 tonne fiducial) LAr TPC operating at LNGS depth (3,800 meters of water equivalent). The results show that such a detector could measure the CNO neutrino rate with ∼15% precision, and significantly improve the precision of the {sup 7}Be and pep neutrino rates compared to the currently available results from the Borexino organic liquid scintillator detector.
We reanalyze data collected with the DarkSide-50 experiment and recently used to set limits on the spin-independent interaction rate of weakly interacting massive particles (WIMPs) on argon nuclei ...with an effective field theory framework. The dataset corresponds to a total (16660 ± 270) kg d exposure using a target of low-radioactivity argon extracted from underground sources. We obtain upper limits on the effective couplings of the 12 leading operators in the nonrelativistic systematic expansion. For each effective coupling we set constraints on WIMP-nucleon cross sections, setting upper limits between 2.4 × 10−45 cm2 and 2.3 × 10−42 cm2 ( 8.9 × 10−45 cm2 and 6.0 × 10−42 cm2 ) for WIMPs of mass of 100 GeV/c2 ( 1000 GeV/c2) at 90% confidence level.
The data acquisition architecture for the tracking detector of the MECO experiment will consist of a preamplifier/discriminator feeding a buffered digitizer which will be controlled by programmable ...logic. The digitizer converts the timing and analog waveform into digital storage for later readout. In order to evaluate this conceptual design, a prototype system was assembled using an existing digitizer chip, which had similar characteristics to the one proposed for MECO. In this prototype system, the event readout sequence and trigger was controlled by a Xilinx FPGA, and gated data events were transferred for further processing to higher levels in the data stream. The system contained 64 input channels divided into four groups of 16 channels, and either anode or cathode signals could be processed. It could be operated in either an internal or external trigger mode. Test results are reported in this paper, including the maximum event rate, the system dead time, and the relationship between the system efficiency and the hitmap selection. Based on these test results, some improvements in the digitizer chip are discussed, and the specifications of our proposed digitizer are presented.
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