443 research outputs found
Coupling of Baryon Resonances to the channel
We estimate the resonance coupling strength and
from a Vector Meson Dominance (VMD) analysis. The isoscalar and isovector part
of the photon coupling are obtained separately from helicity amplitudes. The
reliability of this approach is tested by comparing VMD predictions for
with values obtained from fitting the hadronic decay widths into
. A reasonable agreement is found, but VMD tends to underestimate the
coupling constants. In order to confirm consistency with experimental data, we
calculate the cross-sections for photon-and pion induced reactions within a
{\it Breit-Wigner} model. Finally, we study how the properties of
mesons in nuclear matter are affected from the excitation of resonance-hole
loops. For an at rest, we find a broadening of about 40 MeV, while at
higher momenta the effect of resonance excitations is reduced.Comment: 21 pages, 5 ps figures, misprints corrected, discussion added,
improved calculation of gamma N -> omega N, revised version to be published
in Nuclear Physics
Vector Mesons and Baryon Resonances in Nuclear Matter
We calculate the effect of many-body interactions in nuclear matter on the
spectral function of and meson. In particular, we focus on the
role played by baryon resonances in this context.Comment: 4 pages, 4 figures, to be published in proceedings of the Third
International Conference on Perspectives on Hadronic Physics, 7 - 11 May
2001, Miramare-Trieste, Ital
Vector Meson Decay of Baryon Resonances
We investigate the coupling of vector mesons with nucleons to nucleon
resonances in an isospin-selective VMD approach and explore the in-medium
properties of vector mesons.Comment: 8 pages, 2tables, 4 figures, invited talk at NSTAR 2001, Workshop on
the Physics of Excited Nucleons, University of Mainz, Germany, March 7-10,
2001. To be published in World Scientifi
Exclusive pion electroproduction off nucleons and nuclei
We present our results for the exclusive electroproduction of pions off
nucleons and nuclei at high values of . In electroproduction of nuclei
we consider the Color Transparency (CT) effect recently observed
at JLAB. It is shown that the description of production off nucleons is
mandatory for the proof of the CT signal at JLAB. We further develop the models
for exclusive production of off nucleons at JLAB and HERMES. At first we
describe a model based on exclusive-inclusive connection. In the second
approach we combine a Regge pole approach with the residual effect of nucleon
resonances. The nucleon resonances are described using a dual connection
between the exclusive form factors and inclusive deep inelastic structure
functions. We present the results for the beam spin azimuthal asymmetries
measured at JLAB in exclusive electroproduction of charged and neutral pions.Comment: 15 pages, 10 figures. Invited talk at the NAPP 2010 - 3rd
International Conference on Nuclear and Particle Physics with CEBAF, October
3rd to 8th 2010, Dubrovnik, Croati
Deep exclusive electroproduction of at HERMES
Deeply virtual electroproduction of pion in exclusive reaction
is studied using a two-component model which includes soft
hadronic and hard partonic reaction mechanisms. The results are compared with
the experimental data measured at HERMES in the deep inelastic region for
values of GeV and GeV. At forward angles the
cross section is longitudinal and is dominated by exchange of Regge poles, with
the dominant trajectory. The off-forward region with GeV is
transverse and shows the dominance of partonic subprocesses. An implication of
present results for the future JLAB facilities are briefly discussed.Comment: 10 pages, 4 figure
Kaon production from 1 to 40 A GeV
Kaon production is studied within the Giessen Boltzmann-Uehling-Uhlenbeck
(GiBUU) model. Results are compared with experiment and with other models. The
influence of the kaon potential on the kaon azimuthal distributions at SIS
energies is considered. We also discuss the role of the many-body collisions at
high-density phase of reaction.Comment: 6 pages, 4 figures, Proc. of the Int. Workshop on Hot and Dense
Matter in Relativistic Heavy Ion Collisions, 09-12.04.2006, Budapes
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