Diapositiva 1

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L.P. Kaptari (BLTP JINR Dubna FZ Rossendorf)
L.P. Kaptari (BLTP JINR Dubna FZ Rossendorf)
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Propagation of broad meson resonances in a BUU
type transport model Application to di-electron
production.H.W. Barz,B. Kampfer, Gy. Wolf, M.
Zetenyi nucl-th/0605036
Direct
Dalitz decay
Bremssrahlung
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Bonn with only four mesons
The (covariant, relat. inv. ) amplitude
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Vertex Form Factors
1.
Bonn
2.
Electromagnetic FFs
VMD ? (double count.)
ISI FSI (The Jost function formalism
for FSI. Important only at the upper kinematical
limit of the di-lectron mass)
Coupling Constants (R. Shyam U.Mosel,
PRC67 (2003) 065202)
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Fixing parameters
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Gauge Invariance
a)
b)
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Results for the neutron
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Soft Photon Approximation
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(intermediate) summary contact terms in pn
bremsstrahlung are predominant!
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VMD
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Delta contribution
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Tagging the pn reaction in the spectator
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SUMMARY
An effective model based on direct calculation of
the Feynman diagrams is proposed to
parametrize, in a consistent way, the amplitudes
for the dielectron production in
pp, pn and pD
Bremsstrahlung contribution is important in the
whole kinematical region of the di-electron mass
and at relatively low initial energies. Without
the contact terms our results are compatible
with the soft Photon Approximation and with
calculations by other authors. Contact terms,
needed to restore the gauge invariance, play a
predominant role in the bremsstrahlung amplitude
in pn-reactions (in view of such circumstance, a
more consistent investigation of the recipes of
restoration the GI would be valuable here). Our
approach can be easily generalized to Dp
reactions. Within a covariant Bethe Salpeter
formalism by using the previously found solution
of the BS equation (with the same OBE potential)
we demonstrate that detecting the spectator
protons with velocities close to the deuteron
initial velocity and with momenta in the
forward direction it is possible to study
experimentally the pn
sub-reaction with neutron targets.