DOI 10.1007/s100529801006
Three jet cross sections in photoproduction at HERA
M. Klasen
High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA (e-mail: klasen@hep.anl.gov)
Received: 5 August 1998 / Published online: 19 October 1998
Abstract
We calculate three jet cross sections in photoproduction using exact matrix
elements for the direct and resolved contributions. Numerical distributions
are presented in a generic, irreducible set of variables that allows to
disentangle the dynamics of partonic QCD subprocesses from each other and
from pure phase space distributions. The results are compared to preliminary
data from the ZEUS collaboration at HERA. It is found that the largest
contribution comes from photon-gluon
fusion in the mass range 36 GeV 
80 GeV.
The measured leading jet scattering angle distribution is consistent with the
t-channel exchange of a massless fermion in 
scattering,
where the third parton is assumed to arise from soft bremsstrahlung. The data
are inconsistent with pure phase space and Rutherford scattering distributions.
Copyright Springer-Verlag
