964 research outputs found

    B-meson decay constants: a more complete picture from full lattice QCD

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    We extend the picture of BB-meson decay constants obtained in lattice QCD beyond those of the BB, BsB_s and BcB_c to give the first full lattice QCD results for the B∗B^*, Bs∗B^*_s and Bc∗B^*_c. We use improved NonRelativistic QCD for the valence bb quark and the Highly Improved Staggered Quark (HISQ) action for the lighter quarks on gluon field configurations that include the effect of u/du/d, ss and cc quarks in the sea with u/du/d quark masses going down to physical values. For the ratio of vector to pseudoscalar decay constants, we find fB∗/fBf_{B^*}/f_B = 0.941(26), fBs∗/fBsf_{B^*_s}/f_{B_s} = 0.953(23) (both 2σ2\sigma less than 1.0) and fBc∗/fBcf_{B^*_c}/f_{B_c} = 0.988(27). Taking correlated uncertainties into account we see clear indications that the ratio increases as the mass of the lighter quark increases. We compare our results to those using the HISQ formalism for all quarks and find good agreement both on decay constant values when the heaviest quark is a bb and on the dependence on the mass of the heaviest quark in the region of the bb. Finally, we give an overview plot of decay constants for gold-plated mesons, the most complete picture of these hadronic parameters to date.Comment: 20 pages, 9 figures. Minor updates to the discussion in several places and some additional reference

    Report on R. V. Akademik Vernadsky cruise 39, stage IV, June 17 - July 17, 1989

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    Participation by U. S. personnel on Cruise 39, Leg IV (June 17 - July 17, 1989) of the Marine Hydrophysical Institute's research vessel Akademik Vernadsky provided valuable information, documented in the present report for planning future cooperative projects with Soviet oceanographers. Detailed descriptions are given of the ship, its scientific laboratories, computers and onboard instrumentation. Planning and operating procedures are described and examples are given of daily work plans, seminars, menus and social activities. Personal accounts by the U. S. participants are also included. Many of the shipboard activities were recorded on VHS video cassettes. The oceanographic data collected in the Gulf Stream survey region during Leg IV are documented in the report. Copies of data sets were provided to the U. S. participants in exchange for U. S. data from the region during the survey period.Funding was provided by Vetelsen, the Education Office of Woods Hole Oceanographic Institution, and a Dr. Willam B. Richardson Summer Fellowship provided by Alden Products Company

    Conceptualizing the Science-Practice Interface: Lessons from a Collaborative Network on the Front-Line of Climate Change

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    The gap between science and practice is widely recognized as a major concern in the production and application of decision-relevant science. This research analyzed the roles and network connections of scientists, service providers, and decision makers engaged in climate science and adaptation practice in Alaska, where rapid climate change is already apparent. Our findings identify key actors as well as significant differences in the level of bonding ties between network members who perceive similarity in their social identities, bridging ties between network members across different social groups, and control of information across roles—all of which inform recommendations for adaptive capacity and the co-production of usable knowledge. We also find that some individuals engage in multiple roles in the network suggesting that conceptualizing science policy interactions with the traditional categories of science producers and consumers oversimplifies how experts engage with climate science, services, and decision making. Our research reinforces the notion that the development and application of knowledge is a networked phenomenon and highlights the importance of centralized individuals capable of playing multiple roles in their networks for effective translation of knowledge into action

    Research Proposal for an Experiment to Search for the Decay {\mu} -> eee

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    We propose an experiment (Mu3e) to search for the lepton flavour violating decay mu+ -> e+e-e+. We aim for an ultimate sensitivity of one in 10^16 mu-decays, four orders of magnitude better than previous searches. This sensitivity is made possible by exploiting modern silicon pixel detectors providing high spatial resolution and hodoscopes using scintillating fibres and tiles providing precise timing information at high particle rates.Comment: Research proposal submitted to the Paul Scherrer Institute Research Committee for Particle Physics at the Ring Cyclotron, 104 page

    Advanced modelling of the Planck-LFI radiometers

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    The Low Frequency Instrument (LFI) is a radiometer array covering the 30-70 GHz spectral range on-board the ESA Planck satellite, launched on May 14th, 2009 to observe the cosmic microwave background (CMB) with unprecedented precision. In this paper we describe the development and validation of a software model of the LFI pseudo-correlation receivers which enables to reproduce and predict all the main system parameters of interest as measured at each of the 44 LFI detectors. These include system total gain, noise temperature, band-pass response, non-linear response. The LFI Advanced RF Model (LARFM) has been constructed by using commercial software tools and data of each radiometer component as measured at single unit level. The LARFM has been successfully used to reproduce the LFI behavior observed during the LFI ground-test campaign. The model is an essential element in the database of LFI data processing center and will be available for any detailed study of radiometer behaviour during the survey.Comment: 21 pages, 15 figures, this paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jins

    Cross-talk compensation of hyperfine control in donor qubit architectures

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    We theoretically investigate cross-talk in hyperfine gate control of donor-qubit quantum computer architectures, in particular the Kane proposal. By numerically solving the Poisson and Schr\"{o}dinger equations for the gated donor system, we calculate the change in hyperfine coupling and thus the error in spin-rotation for the donor nuclear-electron spin system, as the gate-donor distance is varied. We thus determine the effect of cross-talk - the inadvertent effect on non-target neighbouring qubits - which occurs due to closeness of the control gates (20-30nm). The use of compensation protocols is investigated, whereby the extent of crosstalk is limited by the application of compensation bias to a series of gates. In light of these factors the architectural implications are then considered.Comment: 15 pages, 22 figures, submitted to Nanotechnolog

    ‘I’ve got lots of gaps, but I want to hang on to the ones that I have’: The ageing body, oral health and stories of the mouth

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    The mouth may be presented and understood in different ways, be subject to judgement by others and, as we age, may intrude on everyday life due to problems that affect oral health. However, research that considers older people's experiences concerning their mouths and teeth is limited. This paper reports on qualitative research with 43 people in England and Scotland, aged 65–91, exploring the significance of the mouth over the lifecourse. It uses the concept of ‘mouth talk’ to explore narratives of maintaining, losing and replacing teeth. Participants engaged in ‘mouth talk’ to downplay the impact of the mouth, demonstrate socially appropriate ageing, and distance themselves from ‘real’ old age by retaining a moral identity and sense of self. They also found means to challenge dominant discourses of ageing in how they spoke about missing teeth. Referring to Leder's notion of ‘dys-appearance’ and Gilleard and Higgs’ work on the social imaginary of the fourth age, the study illustrates the ways in which ‘mouth talk’ can contribute to sustaining a sense of self in later life, presenting the ageing mouth, with and without teeth, as an absent presence. It also argues for the importance of listening to stories of the mouth in order to expand understanding of people's approaches to oral health in older age

    LFI 30 and 44 GHz receivers Back-End Modules

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    The 30 and 44 GHz Back End Modules (BEM) for the Planck Low Frequency Instrument are broadband receivers (20% relative bandwidth) working at room temperature. The signals coming from the Front End Module are amplified, band pass filtered and finally converted to DC by a detector diode. Each receiver has two identical branches following the differential scheme of the Planck radiometers. The BEM design is based on MMIC Low Noise Amplifiers using GaAs P-HEMT devices, microstrip filters and Schottky diode detectors. Their manufacturing development has included elegant breadboard prototypes and finally qualification and flight model units. Electrical, mechanical and environmental tests were carried out for the characterization and verification of the manufactured BEMs. A description of the 30 and 44 GHz Back End Modules of Planck-LFI radiometers is given, with details of the tests done to determine their electrical and environmental performances. The electrical performances of the 30 and 44 GHz Back End Modules: frequency response, effective bandwidth, equivalent noise temperature, 1/f noise and linearity are presented

    Thermal susceptibility of the Planck-LFI receivers

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    This paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jinst . This paper describes the impact of the Planck Low Frequency Instrument front end physical temperature fluctuations on the output signal. The origin of thermal instabilities in the instrument are discussed, and an analytical model of their propagation and impact on the receivers signal is described. The experimental test setup dedicated to evaluate these effects during the instrument ground calibration is reported together with data analysis methods. Finally, main results obtained are discussed and compared to the requirements.Comment: This is an author-created, un-copyedited version of an article accepted for publication in Journal of Instrumentation. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at 10.1088/1748-0221/4/12/T1201
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