Speaker
Nataliia Zakharchuk
(Deutsches Elektronen-Synchrotron (DE))
Description
The cross sections for the photoproduction of $D^\star$ mesons have been measured with the ZEUS detector at HERA at three different $ep$ centre-of-mass energies, $\sqrt{s}$, of 318, 251 and 225\,GeV. For each data set, $D^\star$ mesons were required to have a transverse momentum, $p_T^{D^\star}$, and pseudorapidity, $\eta^{D^\star}$, in the ranges, $1.9 < p_T^{D^\star} < 20$\,GeV and $|\eta^{D^\star}|<1.6$, respectively. The events were required to have a virtuality of the incoming photon, $Q^2$, of less than 1 GeV$^2$ and three different photon-proton centre-of-mass energies, corresponding to the same value of $y$, the fraction of the incoming electron momentum carried by the photon. The dependence on $\sqrt{s}$ was studied by normalising to the high-statistics measurement at $\sqrt{s} =318$ GeV. This led to the cancellation of a number of systematic effects both in data and in theory. Predictions from next-to-leading-order QCD describe well the energy dependence in data.
Author
Matthew Wing
(UCL)
