105,075 research outputs found

    Poincare submersions

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    We prove two kinds of fibering theorems for maps X --> P, where X and P are Poincare spaces. The special case of P = S^1 yields a Poincare duality analogue of the fibering theorem of Browder and Levine.Comment: Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol5/agt-5-2.abs.html Version 5: Statement of Theorem B corrected, see footnote p2

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    Ultra-peripheral collisions and hadronic structure

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    Ultra-peripheral collisions are the energy frontier for photon-mediated interactions, reaching, at the Large Hadron Collider (LHC), γp\gamma-p center of mass energies five to ten times higher than at HERA and reaching γγ\gamma\gamma energies higher than at LEP. Photoproduction of heavy quarkonium and dijets in pppp and pApA collisions probes the gluon distribution in protons at Bjorken-xx values down to 3×1063\times10^{-6}, far smaller than can be otherwise studied. In AAAA collisions, these reactions probe the gluon distributions in heavy ions, down to xx values of a few 10510^{-5}. Although more theoretical work is needed to nail down all of the uncertainties, inclusion of these data in current parton distribution function fits would greatly improve the accuracy of the gluon distributions at low Bjorken-xx and low/moderate Q2Q^2. High-statistics ρ0\rho^0 data probe the spatial distribution of the interaction sites; the site distribution is given by the Fourier transform of dσ/dtd\sigma/dt. After introducing UPCs, this review presents recent measurements of dilepton production and light-by-light scattering and recent data on proton and heavy nuclei structure, emphasizing results presented at Quark Matter 2017 (QM2017).Comment: 8 pages, present at Quark Matter 2017 Final version, w/ 1 replaced figure and a few new reference

    Inhomogeneous Shadowing Effects on J/\psi Production in dA Collisions

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    We study the effect of spatially homogeneous and inhomogeneous shadowing on J/ψJ/\psi production in deuterium-nucleus collisions. We discuss how the shadowing and its spatial dependence may be measured by comparing central and peripheral dAdA collisions. These event classes may be selected by using gray protons from heavy ion breakup and events where the proton or neutron in the deuterium does not interact. We find that inhomogenous shadowing has a significant effect on central dAdA collisions, larger than is observed in central AAAA collisions. The inhomogeneity may be measured by comparing the rapidity dependence of J/ψJ/\psi production in central and peripheral collisions. Results are presented for ddAu collisions at sNN=200\sqrt{s_{NN}} = 200 GeV and ddPb collisions at sNN=6.2\sqrt{s_{NN}} = 6.2 TeV.Comment: 10 pgs with 3 figure

    A dynamic response and eye scanning data base useful in the development of theories and methods for the description of control/display relationships

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    A set of specially prepared digital tapes is reported which contain synchronized measurements of pilot scanning behavior, control response, and vehicle response obtained during instrument landing system approaches made in a fixed-base DC-8 transport simulator. The objective of the master tape is to provide a common data base which can be used by the research community to test theories, models, and methods for describing and analyzing control/display relations and interactions. The experimental conditions and tasks used to obtain the data and the detailed format of the tapes are described. Conventional instrument panel and controls were used, with simulated vertical gust and glide slope beam bend forcing functions. Continuous pilot eye fixations and scan traffic on the panel were measured. Both flight director and standard localizer/glide slope types of approaches were made, with both fixed and variable instrument range sensitivities

    ARIANNA: A radio detector array for cosmic neutrinos on the Ross Ice Shelf

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    ARIANNA (The Antarctic Ross Ice Shelf Antenna Neutrino Array) is a proposed 100 km^3 detector for ultra-high energy (above 10^17 eV) astrophysical neutrinos. It will study the origins of ultra-high energy cosmic rays by searching for the neutrinos produced when these cosmic rays interact with the cosmic microwave background. Over 900 independently operating stations will detect the coherent radio Cherenkov emission produced when astrophysical neutrinos with energy above 10^17 eV interact in the Antarctic Ross Ice Shelf. Each station will use 8 log periodic dipole antennas to look for short RF pulses, with the most important frequencies between 80 MHz and 1 GHz. By measuring the pulse polarization and frequency spectrum, the neutrino arrival direction can be determined. In one year of operation, the full array should observe a clear GZK neutrino signal, with different models predicting between 3 and 51 events, depending on the nuclear composition of the cosmic-rays and on the cosmic evolution of their sources.Comment: 8 pages, presented at SORMA12. Many small improvements, per referee comment
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