Charmed hadron production in an improved quark coalescence model

We study the production of charmed hadrons D0 and Λc+ in relativistic heavy ion collisions using the charm quark coalescence. Besides taking into consideration changing hadron sizes in a hot dense medium, which results in an enhanced coalescence probability for charm quarks of very low transverse momenta, we also include the collective flow effect on heavier resonances, which leads to a shift of massive charmed resonances to larger transverse momenta. Including the conversion of charm quarks not undergoing coalescence to hadrons by independent fragmentation, we obtain a good description of the measured yield ratio Λc+/D0 as a function of transverse momentum in Au+Au collisions at sNN=200 GeV by the STAR Collaboration at the Relativistic Heavy Ion Collider.