Flavoured aspects of the QCD thermodynamics

We discuss recent progress in lattice QCD studies on various aspects involving strange and heavy quarks. Appropriate combinations of conserved net strange and net charm fluctuations and their correlations with other conserved charges provide evidence that in the hadronic phase so far unobserved hadrons contribute to the thermodynamics and need to be included in hadron resonance gas models. In the strange sector this leads to significant reductions of the chemical freeze-out temperature of strange hadrons. We have found that a description of the thermodynamics of open strange and open charm degrees of freedom in terms of an uncorrelated hadron gas is valid only up to temperatures close to the chiral crossover temperature. This suggests that in addition to light and strange hadrons also open charm hadrons start to dissolve already close to the chiral crossover. Further indications that open charm mesons start to melt in the vicinity of Tc is obtained from an analysis of screening masses, while in the charmonium sector these screening masses show a behavior compatible with a sequential melting pattern. In the last section we discuss resent progress in extracting a transport coefficient, the heavy quark momentum diffusion coefficient, based on continuum extrapolated color-electric field correlation functions and estimate the time scale associated with the kinetic equilibration of heavy quarks. Close to Tc this suggests that charm quark kinetic equilibration appears almost as fast as that of light partons in agreement with qualitative discoveries at RHIC and LHC that charm quarks appear to flow about as effectively as light quarks. 1. Additional strange hadrons and strangeness freeze-out in Heavy Ion Collisions Fluctuations and correlations of conserved quantum numbers like baryon number B, electric charge Q, strangeness S and charm C are important quantities that can be used to analyze different contributions to thermodynamic quantities. Especially in the strange and charm sector they can serve as probes for the liberation of degrees of freedom and the appearance of fractional charge quantum numbers, e.g. by comparing to the limiting cases, i.e. Hadron Resonance Gas (HRG) in the hadronic phase and the non-interaction Stefan Boltzmann limit at high temperatures. Furthermore, by comparing to hadron resonance gas models information on the abundance of open strange and open charm hadrons can be gained. The mesonic (M) and baryonic (B) pressure contributions of open strange hadrons in the hadron resonance gas model, using the classical Boltzmann approximation, can be evaluated separately by summing over all open strange mesons and baryons respectively, P M/B(T, ~μ) = T 4 2π2 ∑ i∈X gi (mi T )2 K2(mi/T ) · cosh (Biμ̂B +Qiμ̂Q + Siμ̂S) , (1) 15th International Conference on Strangeness in Quark Matter (SQM2015) IOP Publishing Journal of Physics: Conference Series 668 (2016) 012003 doi:10.1088/1742-6596/668/1/012003 Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1