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The Q2 dependence of dijet cross sections in γp interactions at HERA
Journal article   Peer reviewed

The Q2 dependence of dijet cross sections in γp interactions at HERA

ZEUS Collaboration, J. Repond and U. Mallik
Physics letters. B, Vol.479(1), pp.37-52
04/2000
DOI: 10.1016/S0370-2693(00)00311-7
url
https://arxiv.org/pdf/hep-ex/0002010View
Open Access

Abstract

The dependence of the photon structure on the photon virtuality, Q2, is studied by measuring the reaction e+p → e+ + jet + jet + X at photon-proton centre-of-mass energies 134 < W < 223 GeV. Events have been selected in the Q2 ranges ≃ 0 GeV2, 0.1-0.55 GeV2, and 1.5-4.5 GeV2, having two jets with transverse energy E(T)/(jet) > 5.5 GeV in the final state. The dijet cross section has been measured as a function of the fractional momentum of the photon participating in the hard process, x(γ)/(OBS). The ratio of the dijet cross section with x(γ)/(OBS) < 0.75 to that with x(γ)/(OBS) > 0.75 decreases as Q2 increases. The data are compared with the predictions of NLO pQCD and leading-order Monte Carlo programs using various parton distribution functions of the photon. The measurements can be interpreted in terms of a resolved photon component that falls with Q2 but remains present at values of Q2 up to 4.5 GeV2. However, none of the models considered gives a good description of the data.

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