105,075 research outputs found
Poincare submersions
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
Ultra-peripheral collisions and hadronic structure
Ultra-peripheral collisions are the energy frontier for photon-mediated
interactions, reaching, at the Large Hadron Collider (LHC), center
of mass energies five to ten times higher than at HERA and reaching
energies higher than at LEP. Photoproduction of heavy quarkonium
and dijets in and collisions probes the gluon distribution in protons
at Bjorken- values down to , far smaller than can be
otherwise studied. In collisions, these reactions probe the gluon
distributions in heavy ions, down to values of a few . 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- and
low/moderate . High-statistics data probe the spatial
distribution of the interaction sites; the site distribution is given by the
Fourier transform of .
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
We study the effect of spatially homogeneous and inhomogeneous shadowing on
production in deuterium-nucleus collisions. We discuss how the
shadowing and its spatial dependence may be measured by comparing central and
peripheral 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 collisions, larger than is observed in
central collisions. The inhomogeneity may be measured by comparing the
rapidity dependence of production in central and peripheral
collisions. Results are presented for Au collisions at
GeV and Pb collisions at 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
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
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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