Abstract
We analyze the pseudo-critical behavior of three-flavor QCD using highly improved staggered quarks (HISQ) on lattices with temporal extent $N_\tau =8$ and for quark masses corresponding to a pseudoscalar Goldstone mass in the range $80 ~ {\rm MeV} ~ \lesssim ~ m_\pi ~ \lesssim ~ 140 ~ {\rm MeV}$. Our findings are consistent with the occurrence of a second order chiral phase transition at vanishing values of the quark masses. The chiral phase transition temperature at this finite value of the lattice spacing is determined to be $T_c = 98_{-6}^{+3}~{\rm MeV}$. A comparison with a corresponding analysis performed in (2+1)-flavor QCD suggests that the continuum limit extrapolated chiral phase transition temperature in 3-flavor QCD will turn out to be below $90 ~ {\rm MeV}$.
Highlights
The nature of the QCD chiral phase transition as a function of the number of light flavors and the value of the quark masses has been the subject of intense and ongoing study ever since the first work of Pisarski and Wilczek [1]
We analyze the pseudocritical behavior of three-flavor QCD using highly improved staggered quarks on lattices with temporal extent Nτ 1⁄4 8 and for quark masses corresponding to a pseudoscalar Goldstone mass in the range 80 MeV ≲ mπ ≲ 140 MeV
The calculations for Nτ 1⁄4 6 [10] have been performed at various temperature values, keeping the quark mass fixed in units of the lattice spacing while in our current calculations on Nτ 1⁄4 8 lattices the quark mass is varied along a line of constant physics by keeping the ratio H fixed
Summary
The nature of the QCD chiral phase transition as a function of the number of light flavors and the value of the quark masses has been the subject of intense and ongoing study ever since the first work of Pisarski and Wilczek [1]. Lattice studies have provided strong evidence for the expected second order nature of the chiral phase transition in the two-flavor chiral limit for physical value of the strange quark mass. The functional RG analysis of the three-flavor chiral transition, suggests that a first order transition, only occurs for rather small values of the pion mass, mπ ≲ 25 MeV This is in accordance with lattice QCD calculations using staggered fermions. In the study presented here we want to further explore the nature of the chiral phase transition in three-flavor QCD and, in particular, provide a first estimate of the chiral phase transition temperature based on calculations with the highly improved staggered quark (HISQ) action.
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