73 research outputs found

    Development of New Off-Axis Near Detector Samples for the T2K Oscillation Analysis

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    The Tokai-to-Kamioka (T2K) experiment is a long-baseline (anti)neutrino experiment designed to make world-leading measurements of several of the parameters that describe neutrino oscillations: θ13\theta_{13}, θ23\theta_{23}, Δm232\Delta m^2_{23} and δCP\delta_{CP}. The experiment uses a beam of muon (anti)neutrinos produced at the Japan Proton Accelerator Research Complex (J-PARC) which is categorised by a suite of near detectors before oscillation samples are selected at the far detector, Super-Kamiokande. Charged Current (CC) νμ\nu_{\mu} interactions in the near detector ND280 are categorised based on reconstructed final state particles. The resulting samples are fitted to near detector data to provide constraints on flux and cross section systematic uncertainties in the oscillation analysis. In this thesis, a new selection of CC νμ\nu_{\mu} interactions in the ND280 detector that produce final state photons is developed. The new photon sample has an efficiency of 43.0±\pm0.1\% (43.9±\pm0.1\%) and a purity of 53.9±\pm0.2\% (54.2±\pm0.2\%) in FGD1 (FGD2). Detector systematic uncertainties associated with the new selections are also evaluated. The new photon sample, along with a new proton tag, are used in a new categorisation of CC νμ\nu_{\mu} interactions at the near detector in the oscillation analysis. One of the fitting methods used to fit the near detector data is described in this thesis. The new near detector samples are used to constrain uncertainties in the flux and cross section models used in the analysis, reducing the uncertainties on the far detector event rates

    Simultaneous measurement of the muon neutrino charged-current cross section on oxygen and carbon without pions in the final state at T2K

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    This paper reports the first simultaneous measurement of the double differential muon neutrino charged-current cross section on oxygen and carbon without pions in the final state as a function of the outgoing muon kinematics, made at the ND280 off-axis near detector of the T2K experiment. The ratio of the oxygen and carbon cross sections is also provided to help validate various models' ability to extrapolate between carbon and oxygen nuclear targets, as is required in T2K oscillation analyses. The data are taken using a neutrino beam with an energy spectrum peaked at 0.6~GeV and comprises 57.34×\times1019^{19} protons on target. The extracted measurement is compared with the prediction from different Monte Carlo neutrino-nucleus interaction event generators, showing particular model separation for very forward-going muons. Overall, of the models tested, the result is best described using Local Fermi Gas descriptions of the nuclear ground state with RPA suppression

    Genome sequences of four cluster P mycobacteriophages

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    Four bacteriophages infecting Mycobacterium smegmatis mc2155 (three belonging to subcluster P1 and one belonging to subcluster P2) were isolated from soil and sequenced. All four phages are similar in the left arm of their genomes, but the P2 phage differs in the right arm. All four genomes contain features of temperate phages

    The impact of large scale licensing examinations in highly developed countries: a systematic review

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    BACKGROUND: To investigate the existing evidence base for the validity of large-scale licensing examinations including their impact. METHODS: Systematic review against a validity framework exploring: Embase (Ovid Medline); Medline (EBSCO); PubMed; Wiley Online; ScienceDirect; and PsychINFO from 2005 to April 2015. All papers were included when they discussed national or large regional (State level) examinations for clinical professionals, linked to examinations in early careers or near the point of graduation, and where success was required to subsequently be able to practice. Using a standardized data extraction form, two independent reviewers extracted study characteristics, with the rest of the team resolving any disagreement. A validity framework was used as developed by the American Educational Research Association, American Psychological Association, and National Council on Measurement in Education to evaluate each paper’s evidence to support or refute the validity of national licensing examinations. RESULTS: 24 published articles provided evidence of validity across the five domains of the validity framework. Most papers (n = 22) provided evidence of national licensing examinations relationships to other variables and their consequential validity. Overall there was evidence that those who do well on earlier or on subsequent examinations also do well on national testing. There is a correlation between NLE performance and some patient outcomes and rates of complaints, but no causal evidence has been established. CONCLUSIONS: The debate around licensure examinations is strong on opinion but weak on validity evidence. This is especially true of the wider claims that licensure examinations improve patient safety and practitioner competence

    Global Spatial Risk Assessment of Sharks Under the Footprint of Fisheries

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    Effective ocean management and conservation of highly migratory species depends on resolving overlap between animal movements and distributions and fishing effort. Yet, this information is lacking at a global scale. Here we show, using a big-data approach combining satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively) and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of high-seas fishing effort. Results demonstrate an urgent need for conservation and management measures at high-seas shark hotspots and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real time, dynamic management

    Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

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    A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

    Measurement of the charge asymmetry in top-quark pair production in the lepton-plus-jets final state in pp collision data at s=8TeV\sqrt{s}=8\,\mathrm TeV{} with the ATLAS detector