Universality driven analytic structure of QCD crossover: radius of convergence and QCD critical point

Understand

Recent lattice QCD calculations show strong indications that the crossover of QCD at zero baryon chemical potential ($\mu_B$) is a remnant of the second order chiral phase transition.

• The non-universal parameters needed to map temperature $T$ and $\mu_B$ to the universal properties of the second order chiral phase transition were determined by lattice QCD calculations.
• Motivated by these advances, first, we discuss the analytic structure of the partition function -- the so-called Yang-Lee edge singularity -- in the QCD crossover regime, solely based on universal properties.
• Then, utilizing the lattice calculated non-universal parameters, we map this singularity to the real $T$ and complex $\mu_B$ plane, in order to find the radius of convergence for a Taylor series expansion of QCD partition function around $\mu_B=0$ in the QCD crossover regime.