1,464 research outputs found
An independent estimate of the triple-Pomeron coupling
The value of the important triple-Pomeron coupling is estimated by an
unorthodox procedure using the known diffractive parton distribution functions.
The result is g_{3P}\simeq 0.2g_N, where g_N is the Pomeron-nucleon coupling.
This is in excellent agreement with an independent determination, g_{3P}\simeq
0.2g_N, previously obtained by analysing the available data in the triple-Regge
region with absorptive effects taken into account.Comment: 7 pages, 5 figure
Upsilon photoproduction at HERA compared to estimates of perturbative QCD
We estimate the cross section for gamma p -> Upsilon p by two independent
methods. First, by studying the corrections to the naive leading-order QCD
formula and, second, by using parton-hadron duality. The estimates are in good
agreement with each other and with the recent measurements of the cross section
at HERA.Comment: 9 pages, LaTeX, one figur
Numerical solution of free-boundary problems in fluid mechanics. Part 3. Bubble deformation in an axisymmetric straining flow
We consider the deformation of a bubble in a uniaxial extensional flow for Reynolds numbers in the range 0.1 [less-than-or-eq, slant] R [less-than-or-eq, slant] 100. The computations show that the bubble bursts at a relatively early stage of deformation for R [gt-or-equal, slanted] O(10), never reaching the highly elongated shapes observed and predicted at lower Reynolds numbers. We also compute the deformation of the bubble under the assumption of potential flow, and conclude that the potential-flow solution provides a good approximation to the real flow in this case for R [gt-or-equal, slanted] O(100)
Bubble shapes in steady axisymmetric flows at intermediate Reynolds number
The shape of a gas bubble which rises through a quiescent incompressible, Newtonian fluid at intermediate Reynolds numbers is considered. Exact numerical solutions for the velocity and pressure fields, as well as the bubble shape, are obtained using finite difference techniques and a numerically generated transformation to an orthogonal, boundary-fitted coordinate system. No restriction is placed on the allowable magnitude of deformation
Diffractive rho-meson Leptoproduction on Polarized Nucleon as a Way to Measure the Polarized Gluon Distribution
The amplitude of diffractive (and open quark) leptoproduction on a
polarized target is calculated in the leading log approximation of pQCD using
the hadron-parton duality hypothesis. The spin-spin asymmetry is expressed in
terms of the spin dependent gluon and quark structure functions in the small
region. Therefore the reaction provides a promising
tool to study the spin dependent gluon distribution .Comment: 13 pages, LaTeX, 2 figure
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