A Study of Heavy Flavoured Meson Fragmentation Functions in e+ e- annihilation
Matteo Cacciari, Paolo Nason, Carlo Oleari
TL;DR
Heavy-flavoured meson fragmentation in e+e- annihilation is analyzed with a comprehensive perturbative framework that combines NLO initial conditions, NLO coefficient functions, and NLL Sudakov resummation for both initial-state and final-state contributions, plus a phenomenological non-perturbative component. Mellin-space techniques and bottom-threshold matching are used to control large-x and threshold effects. Fits to CLEO and BELLE data for D and D* show excellent agreement, but evolution to LEP energies reveals tension with ALEPH data unless sizable non-perturbative corrections to coefficient functions are invoked, indicating non-perturbative physics in the hard coefficient sector. The study provides extracted non-perturbative parameters to improve predictions for heavy-flavour production in hadron-hadron and photon-induced processes and highlights the need for careful perturbative/non-perturbative matching across experiments.
Abstract
We compare QCD theoretical predictions for heavy flavoured mesons fragmentation spectra in e+ e- annihilation with data from CLEO, BELLE and LEP. We include several effects in our calculation: next-to-leading order initial conditions, evolution and coefficient functions. Soft-gluon effects are resummed at next-to-leading-log accuracy. A matching condition for the crossing of the bottom threshold in evolution is also implemented at next-to-leading order accuracy. Important initial-state electromagnetic radiation effects in the CLEO and BELLE data are accounted for. We find that, with reasonably simple choices of a non-perturbative correction to the fixed-order initial condition for the evolution, the data from CLEO and BELLE can be fitted with remarkable accuracy. The fitted fragmentation function, when evolved to LEP energies, does not however represent fairly the D* fragmentation spectrum measured by ALEPH. Large non-perturbative corrections to the coefficient functions of the meson spectrum are needed in order to reconcile CLEO/BELLE and ALEPH results. Non-perturbative parameters extracted from the fits to e+ e- fragmentation data for D/D* and B mesons are tabulated. They can be employed in the theoretical predictions for the production of charmed and bottomed mesons in hadron-hadron, photon-hadron and photon-photon collisions.