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T: Fachverband Teilchenphysik
T 26: QCD 2
T 26.4: Talk
Tuesday, February 28, 2012, 17:40–17:55, ZHG 009
Dijet cross sections in photoproduction at HERA — •Inna Makarenko — Notkestrasse 85, DESY, Hamburg, Germany
At high collision energies accessible at ep collider HERA hard hadronic jets can be produced. At leading order, at low virtualities of the exchanged photon, two processes contribute to the jet production. In the direct photon process an almost real photon interacts as a point-like particle with a parton of the proton. In contrast in resolved processes the photon fluctuates to an hadronic state. The measurements of the jet production give an important information about the structure of the photon and the proton. Dijet cross sections have been measured in the reaction ep → e + jet + jet + X with the ZEUS detector using an integrated luminosity of 189 pb−1. Differential cross sections are presented as functions of average jet transverse energy and presudorapidity for dijet events with ETjet1 > 21 GeV, ETjet2 > 17 GeV, −1 < ηjet1(2) < 3 for γ p centre-of-mass energies in range 142 < Wγ p < 293 GeV and photon virtuality Q2 < 1 GeV2. In addition, the dijet cross section was measured as a function of the fraction of the incoming photon momentum taken by the dijet system. The dijet cross sections were also measured as functions of the dijet invariant mass, Mjj and scattering angle in the dijet centre-of-mass system for ETjet1(2) > 17 GeV, −1 < ηjet1(2) < 3 and Mjj > 60 GeV. Next-to-leading order calculations give a good description of the measurements. These measurements can be used to further constraint the gluon component of the proton parton density function at medium to high x.