Charm fragmentation functions in the Nambu-Jona-Lasinio model

We derive the fragmentation function (FF), which describes the probability for a charm quark to emit a D meson with a certain momentum fraction, in the Nambu-Jona-Lasinio model. The corresponding elementary FF is calculated with the quark-meson coupling determined in the Nambu-Jona-Lasinio model involving charm quarks. The FF in the infinite momentum frame is constructed through the jet process governed by the elementary FF, and then evolved to the charm scale, at which it is defined. To prepare the FF suitable for an analysis of D meson production at CLEO, we further match the above FF to that in the finite momentum frame at one loop in QCD. It is shown that the charm quark FF, including the finite momentum effects, leads to theoretical results in agreement with the CLEO data.