Jets with high transverse momenta in photoproduction at HERA

Dijet production in the region of photon virtualities Q"2 < 1 GeV"2 and inelasticities 0.1 < y < 0.9 is investigated with the H1 detector at the ep collider HERA. The data sample comprises data collected during the years 1999 and 2000 with an integrated luminosity of 66.6 pb"-"1. Jets are defined using the inclusive k _p_e_r_p_e_n_d_i_c_u_l_a_r _t_o algorithm with a minimum transverse momentum of the leading jet of 25 GeV. Longitudinal photon momentum fractions of 0.1 < x_#gamma# < 1.0 and longitudinal proton momentum fractions of 0.05 < x_p < 0.7 are reached. The data are compared to Monte Carlo event generators based on LO QCD cross sections and NLO QCD parton level calculations. Both yield a good description of the measured cross sections over a wide kinematical range. In the case of the NLO calculations results obtained using different photon and proton parton densities are found to be in good agreement with the data and yield differences of the same size or smaller than both experimental and theoretical uncertainties. (orig.)SIGLEAvailable from TIB Hannover: RA 8919(2004-047) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman