Measurement of Di-jet Cross-Sections in Photoproduction and Photon Structure

TL;DR

This paper measures di-jet cross-sections in photoproduction at HERA to probe the quark and gluon content of the photon, providing insights into photon structure using experimental data.

Contribution

It presents the first measurement of the effective parton density in the photon at low x_gamma using di-jet events at HERA.

Findings

Measured the differential di-jet cross-section dsigma/dlog(x_gamma).

Derived the gluon density in the photon from the data.

Provided data down to x_gamma=0.05.

Abstract

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 x_gamma 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 dsigma/dlog(x_gamma) 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, E_(T,jet)>6 GeV, the effective parton density f_gamma,eff(x_gamma) = [q(x_gamma) + bar(q)(x_gamma) +9/4g(x_gamma)] in the photon in leading order QCD is measured down to x_gamma=0.05 from which the gluon density in the photon is derived.