Measurement of the charm fragmentation function in D* photoproduction at HERA

The charm fragmentation function has been measured in D* photoproduction with the ZEUS detector at HERA using an integrated luminosity of 120 pb-1. The fragmentation function is measured versus z = (E+p_parallel){D*}/2E{jet}, where E is the energy of the D* meson and p_parallel is the longitudinal momentum of the D* meson relative to the axis of the associated jet of energy E{jet}. Jets were reconstructed using the kT clustering algorithm and required to have transverse energy larger than 9 GeV. The D* meson associated with the jet was required to have a transverse momentum larger than 2 GeV. The measured function is compared to different fragmentation models incorporated in leading-logarithm Monte Carlo simulations and in a next-to-leading-order QCD calculation. The free parameters in each fragmentation model are fitted to the data. The extracted parameters and the function itself are compared to measurements from e+e- experiments.

Note:

19 pages, 5 figures, 3 tables, submitted to JHEP

D*(2010): photoproduction
charm: fragmentation function
fragmentation: model
jet: energy
numerical calculations: Monte Carlo
DESY HERA Stor
D*(2010): longitudinal momentum
transverse momentum dependence
ZEUS
electron p: interaction

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