Critical end points in (2+1)-flavor QCD with imaginary chemical potential

Understand

We present here the results from an ongoing determination of the critical quark mass in simulations of (2+1)-flavor QCD with an imaginary chemical potential.

• Studies with unimproved actions found the existence of a critical quark mass value at which the crossover transition ends on a second order phase transition and becomes first order for smaller values of the quark mass for the case of both vanishing and imaginary chemical potential.
• We use the Highly Improved Staggered Quark (HISQ) action and perform calculations in the Roberge-Weiss (RW) plane, where the value of the critical mass is expected to be largest.
• The lowest quark mass value used in our simulation corresponds to the pion mass $m_\pi$, down to $40$ MeV.