Measurements of open charm hadrons at the STAR experiment

Because of their large masses, charm quarks are predominantly produced in the early stages of the heavy-ion collisions via hard scatterings. Therefore, they experience the entire evolution of the Quark-Gluon Plasma created in such collisions. Compared to light quarks, charm quarks thermalize more slowly. Therefore, the open charm hadrons present a unique probe to the properties of the hot and dense nuclear matter by measuring their energy loss and degree of thermalization in the medium. Furthermore, with the combined measurements of D⁰ and D_s mesons, we can study multiple modes of coalescence of charm quarks with light quarks in heavy-ion collisions. Heavy Flavor Tracker at the STAR experiment enables full topological reconstruction of open charm hadrons which greatly improves measurements of D⁰ mesons and opens the door to reconstructing the D_s mesons for the first time at RHIC. In this paper, we present the nuclear modification factor and azimuthal anisotropy for the D⁰ and D_s mesons as well as the ratio of D_s/D⁰ in Au+Au collisions at the center-of-mass energy $\sqrt{{s}_{{\rm{N}}{\rm{N}}}}=200\,\mathrm{GeV}$.