  Ratios of cumulants of conserved net charge fluctuations are sensitive to the
degrees of freedom that are carriers of the corresponding quantum numbers in
different phases of strong interaction matter. We calculate second and fourth
order cumulants of net charm and strange fluctuations and their correlations
with other conserved charges such as net baryon number and electric charge.
Simulation are performed on $N_\tau$=6 and 8 lattices using the Highly Improved
Staggered Quark (HISQ) action with a light to strange quark mass ratio of 1/20
and having charm quarks treated in the quenched approximation. Analysing
appropriate ratios of these cumulants we observe that both open strange and
charm hadrons start to get dissociated in the chiral crossover region. We
provide indirect evidence for the existence of additional, experimentally yet
unobserved open charm and strange hadrons from QCD thermodynamics. This is done
by comparing lattice QCD results to Hadron Resonance Gas (HRG) model
calculations performed with a hadron spectrum as listed in the Particle Data
Tables as well as with a spectrum predicted in the relativistic quark model and
observed in lattice QCD calculations. We also discuss the influence of these
experimentally yet unobserved states on the determination of freeze-out
temperature and chemical potentials from heavy ion collision experiments. We
found that including these additional states in the HRG model leads to a
systematic 5-8 MeV decrease in the freeze-out temperature of strange hadrons.
