  We use the recently obtained two-loop hard thermal loop perturbation theory
thermodynamics functions of a plasma of quarks and gluons to compute the
diagonal second- and fourth-order quark number susceptibilities. The two-loop
hard thermal loop perturbation theory thermodynamic functions used are reliable
in the limit that the ratio of the quark chemical potential to temperature is
small. Using this result, we are able to obtain (semi-)analytic expressions for
the quark number susceptibilities at leading- and next-to-leading-order in hard
thermal loop perturbation theory. We compare the hard thermal loop perturbation
theory results with perturbative quantum chromodynamics calculations, a
Polyakov-loop Nambu-Jona-Lasinio model calculation, and lattice quantum
chromodynamics results.
