15,836 research outputs found
Isolated photon + jet photoproduction as a tool to constrain the gluon distribution in the proton and the photon
We analyse how the reaction gamma p -> gamma + jet + X can serve to constrain
the gluon distributions. Our results are based on a code of partonic event
generator type which includes full NLO corrections. We conclude that there are
phase space domains in which either the gluon in the photon or the gluon in the
proton give important contributions to the cross section, which should be
observable in HERA experiments.Comment: 22 pages LaTeX, 14 figure
Magnetic relaxation in metallic films: Single and multilayer structures
The intrinsic magnetic relaxations in metallic films will be discussed. It will be shown that the intrinsic damping mechanism in metals is
caused by incoherent scattering of itinerant electron-hole pair
excitations by phonons and magnons. Berger [L. Berger, Phys. Rev. B
54, 9353 (1996)] showed that the interaction between spin waves and
itinerant electrons in multilayers can lead to interface Gilbert
damping. Ferromagnetic resonance (FMR) studies were carried out using
magnetic single and double layer films. The FMR linewidth of the Fe
films in the double layer structures was found to always be larger than
the FMR linewidth measured for the single Fe films having the same
thickness. The increase in the FMR linewidth scaled inversely with the
film thickness, and was found to be linearly dependent on the microwave
frequency. These results are in agreement with Berger's predictions.
(C) 2002 American Institute of Physics
Bethe-Peierls Approximation for Linear Monodisperse Polymers Re-examined
Bethe-Peierls approximation, as it applies to the thermodynamics of polymer
melts, is reviewed. We compare the computed configurational entropy of
monodisperse linear polymer melt with Monte Carlo data available in literature.
An estimation of the configurational contribution to the total liquid's Cp is
presented. We also discuss the relation between Kauzmann paradox and polymer
semiflexibility.Comment: 9 pages, 3 figure
On The {\it Fermi} -Lat Surplus of the Diffuse Galactic Gamma-Ray Emission
Recent observations of the diffuse Galactic \gr emission (DGE) by the {\it
Fermi} Large Area Telescope ({\it Fermi}-LAT) have shown significant
deviations, above a few GeV until about 100 GeV, from DGE models that use the
GALPROP code for the propagation of cosmic ray (CR) particles outside their
sources in the Galaxy and their interaction with the target distributions of
the interstellar gas and radiation fields. The surplus of radiation observed is
most pronounced in the inner Galaxy, where the concentration of CR sources is
strongest. The present study investigates this "{\it Fermi}-LAT Galactic Plane
Surplus" by estimating the \gr emission from the sources themselves, which is
disregarded in the above DGE models. It is shown that indeed the expected hard
spectrum of CRs, still confined in their sources (SCRs), can explain this
surplus. The method is based on earlier studies regarding the so-called EGRET
GeV excess which by now is generally interpreted as an instrumental effect. The
contribution from SCRs is predicted to increasingly exceed the DGE models also
above 100 GeV, up to \gr energies of about ten TeV, where the corresponding
surplus exceeds the hadronic part of the DGE by about one order of magnitude.
Above such energies the emission surplus should decrease again with energy due
to the finite life-time of the assumed supernova remnant sources. Observations
of the DGE in the inner Galaxy at 15 TeV with the Milagro \gr detector and, at
TeV energies, with the ARGO-YBJ detector are interpreted to provide
confirmation of a significant SCR contribution to the DGE.Comment: 6 pages, 1 figure. Accepted for publication in The Astrophysical
Journal, 2013; added referenc
Is a Large Intrinsic k_T Needed to Describe Photon + Jet Photoproduction at HERA?
We study the photoproduction of an isolated photon and a jet based on a code
of partonic event generator type which includes the full set of next-to-leading
order corrections. We compare our results to a recent ZEUS analysis in which an
effective k_T of the incoming partons has been determined. We find that no
additional intrinsic k_T is needed to describe the data.Comment: 23 pages LaTeX, 12 figure
Isolated prompt photon photoproduction at NLO
We present a full next-to-leading order code to calculate the photoproduction
of prompt photons. The code is a general purpose program of partonic event
generator type with large flexibility. We study the possibility to constrain
the photon structure functions and comment on isolation issues. A comparison to
ZEUS data is also shown.Comment: 22 pages LaTeX, 15 figure
A NLO calculation of the hadron-jet cross section in photoproduction reactions
We study the photoproduction of large-p_T charged hadrons in e p collisions,
both for the inclusive case and for the case where a jet in the final state is
also measured. Our results are obtained by a NLO generator of partonic events.
We discuss the sensitivity of the cross section to the renormalisation and
factorisation scales, and to various fragmentation function parametrisations.
The possibility to constrain the parton densities in the proton and in the
photon is assessed. Comparisons are made with H1 data for inclusive charged
hadron production.Comment: 28 pages LaTeX, 14 figure
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