Measurement of inclusive $D^{\ast\pm}$ and associated dijet cross sections in photoproduction at HERA

Abstract

Inclusive photoproduction of D * ± mesons has been measured for photon-proton centre-of-mass energies in the range 130 < W < 280 GeV and photon virtuality Q 2 < 1 GeV 2 . The data sample used corresponds to an integrated luminosity of 37 pb −1 . Total and differential cross sections as functions of the D * transverse momentum and pseudorapidity are presented in restricted kinematical regions and the data are compared with next-to-leading order (NLO) perturbative QCD calculations using the "massive charm" and "massless charm" schemes. The measured cross sections are generally above the NLO calculations, in particular in the forward (proton) direction. The large data sample also allows the study of dijet production associated with charm. A significant resolved as well as a direct photon component contribute to the cross section. Leading order QCD Monte Carlo calculations indicate that the resolved contribution arises from a significant charm component in the photon. A massive charm NLO parton level calculation yields lower cross sections compared to the measured results in a kinematic region where the resolved photon contribution is significant.

Measurement of D ∗ photoproduction at three different centre-of-mass energies at HERA

“…The dominant production mechanism is boson-gluon fusion. Many measurements of charm photoproduction at high ep centre-of-mass energies, √ s = 318 GeV or √ s = 300 GeV, have been made at HERA [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and compared with QCD predictions at next-to-leading order (NLO). The description of the data is generally reasonable, although the uncertainties on the theory are often large.…”