Dijets and photon remnant studies in photoproduction with the ZEUS detector at HERA

Abstract

At the HERA particle accelerator, 27.5 GeV electrons collide with 920 GeV protons. In the photoproduction mode, the quasi-real exchange photon emitted by the electron interacts with the proton at small momentum transfer. Such events are selected and investigated with the ZEUS detector in the photon proton center-of-mass range 130 GeV < Wgamma p < 270 GeV using the 55.1 pb-1 gated luminosity of the year 2000 data. The two typical photoproduction processes are studied separately: in the direct case photons can interact directly with the proton, while in the resolved case the photon is resolved into its hadronic components. An inclusive data sample of two parton jet events with each a minimum transverse energy of 6 GeV and a third jet with a minimum transverse energy of 2 GeV are reconstructed and selected using the inclusive kT clustering algorithm. The third jet travelling in the electron propagation direction can be assumed to be the photon remnant jet. Jet transverse energy density distributions, which are also known as 'jet shapes' are calculated on the jet sample. The photon remnant jets are found to be broader than the parton jets