2020 Impact factor 4.590
Particles and Fields
Eur. Phys. J. C 7, 225-232
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 $< M_{\rm 3-jet} <$ 80 GeV. The measured leading jet scattering angle distribution is consistent with the t-channel exchange of a massless fermion in $2\rightarrow 2$ 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