Measurement of three jet distributions in photoproduction at HERA

The cross section for the photoproduction of events containing three jets with a three-jet invariant mass of M_3J > 50 GeV has been measured with the ZEUS detector at HERA. The three-jet angular distributions are inconsistent with a uniform population of the available phase space but are well described by parton shower models and O(alpha alpha_s^2) pQCD calculations. Comparisons with the parton shower model indicate a strong contribution from initial state radiation as well as a sensitivity to the effects of colour coherence.

Note:

13 pages including 5 figures Report-no: DESY-98-162

positron p: colliding beams
positron p: inclusive reaction
jet: photoproduction
mass spectrum: (3jet)
angular distribution: (3jet)
showers: parton
quantum chromodynamics: perturbation theory
radiation: initial-state interaction
color: coherence
channel cross section

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