Eur. Phys. J. A 11, 345-356 (2001)
Long-range Coulomb forces in DIS: missed radiative corrections?
B.Z. Kopeliovich1, 2, 3, A.V. Tarasov1, 2, 3 and O.O. Voskresenskaya31 Max-Planck Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany
2 Institut für Theoretische Physik der Universität, 93040 Regensburg, Germany
3 Joint Institute for Nuclear Research, Dubna, 141980 Moscow Region, Russia
Boris.Kopeliovich@mpi-hd.mpg.de
(Received: 16 May 2001 / Revised version: 3 July 2001 Communicated by A. Schäfer)
Abstract
The Born approximation, one photon exchange, used for DIS (deep inelastic scattering)
is subject to virtual
radiative corrections which are related to the long-range Coulomb forces. They may
be sizeable for heavy nuclei since 
is not a small parameter. So far,
these corrections are known only for two processes, elastic scattering and
bremsstrahlung on the Coulomb field of a point-like target. While the former
amplitude acquires only a phase, in the latter case also the cross-section is modified. Although the problem of Coulomb corrections
for DIS on nuclei is extremely
difficult, it should be challenged rather than "swept under the carpet" . The
importance of these radiative corrections is questioned in the present paper. We show
that, in the simplest case of a constant hadronic current, the Coulomb corrections
provide a phase to the Born amplitude, therefore the cross-section remains the
same. Inclusion of more realistic hadronic dynamics changes this conclusion. The
example of coherent production of vector mesons off nuclei reveals large effects.
So far a little progress has been made deriving lepton wave functions in the
Coulomb field of an extended target. Employing available results based on the
first-order approximation in , we conclude that the Coulomb corrections
are still important for heavy nuclei. We also consider an alternative approach for
extended nuclear targets, the eikonal approximation, which we demonstrate to
reproduce the known exact results for Coulomb corrections. Calculating
electroproduction of vector mesons, we again arrive at a large deviation from the
Born approximation. We conclude that one should accept with caution the
experimental results for nuclear effects in DIS based on analyses done in the Born
approximation.
25.30.-c - Lepton-induced reactions.
25.30.Rw - Electroproduction reactions.
13.40.-f - Electromagnetic processes and properties.
25.30.Bf - Elastic electron scattering.
© Società Italiana di Fisica, Springer-Verlag 2001
