Measurement of di-jet cross-sections in photoproduction and photon structure

The production of hard di-jet events in photoproduction at HERA is dominated by resolved photon processes in which a parton in the photon with momentum fraction xγ is scattered from a parton in the proton. These processes are sensitive to the quark and gluon content of the photon. The differential di-jet cross-section dσ/dlog(xγ) is presented here, measured in tagged photoproduction at HERA using data taken with the H1 detector, corresponding to an integrated luminosity of 7.2 pb−1. Using a restricted data sample at high transverse jet energy, ET,jet>6 GeV, the effective parton density fγ,eff(xγ)=q(xγ)+q̄(xγ)+9/4g(xγ) in the photon in leading order QCD is measured down to xγ= 0.05 from which the gluon density in the photon is derived.