Open Heavy-Flavor Production in Heavy-Ion Collisions

The ultrarelativistic heavy-ion programs at the Relativistic Heavy Ion Collider and the Large Hadron Collider have entered an era of quantitative analysis of quantum chromodynamics (QCD) at high temperatures. The remarkable discovery of the strongly coupled quark–gluon plasma (sQGP), as deduced from its hydrodynamic behavior at long wavelengths, calls for probes that can reveal its inner workings. Charm- and bottom-hadron spectra offer unique insights into the transport properties and the microscopic structure of the QCD medium created in these collisions. At low momentum the Brownian motion of heavy quarks in the sQGP gives access to their diffusion constant, at intermediate momentum these quarks give insight into hadronization mechanisms, and at high momentum they are expected to merge into a radiative-energy loss regime. We review recent experimental and theoretical achievements on measuring a variety of heavy-flavor observables, characterizing the different regimes in momentum and extracting pertinent transport coefficients to unravel the structure of the sQGP and its hadronization.