End point of the first-order phase transition of QCD in the heavy quark region by reweighting from quenched QCD

Abstract

We study the end point of the first-order deconfinement phase transition in two and 2+1 flavor QCD in the heavy quark region of the quark mass parameter space. We determine the location of critical point at which the first-order deconfinement phase transition changes to crossover, and calculate the pseudo-scalar meson mass at the critical point. Performing quenched QCD simulations on lattices with the temporal extents N t = 6 and 8, the effects of heavy quarks are determined using the reweighting method. We adopt the hopping parameter expansion to evaluate the quark determinants in the reweighting factor. We estimate the truncation error of the hopping parameter expansion by comparing the results of leading and next-toleading order calculations, and study the lattice spacing dependence as well as the spatial volume dependence of the result for the critical point. The overlap problem of the reweighting method is also examined. Our results for N t = 4 and 6 suggest that the critical quark mass decreases as the lattice spacing decreases and increases as the spatial volume increases.

Determination of the endpoint of the first order deconfiniement phase transition in the heavy quark region of QCD

“…However, V eff remains double-well up to quite large K where the hopping parameter expansion is not applicable. Thus, we can not find K ct for N t = 8 with the present method [3].…”

“…We have also tried to calculate K ct on a 36 3 × 6 lattice. However, unlike the cases of 24 3 × 6 and 32 3 × 6 lattices, the overlap problem turned out to be severe on this lattice to obtain a reliable V eff up to the critical point [3]. We come back to the issue of overlap problem in Sec.…”

“…We found that the overlap problem occurs in the determination of K ct on the 36 3 × 6 lattice [3]. As an attempt to avoid the overlap problem, we perform simulations with an effective action for QCD with heavy quarks, S eff = −6N site βP − N 3 s λ ReΩ.…”

Deconfinement in the presence of a strong magnetic field

“…(The continuum extrapolation, however, remains elusive.) For a rough comparison to a recent work [55], the study reported m PS =T CEP ¼ ð15.73; 11.15Þ for N t ¼ ð4; 6Þ in 2-flavor QCD system (NLO). In our 2-flavor model, taking the pseudoscalar mass m PS ≈ 2m crit , with m crit ≈ 1.353 GeV and T CEP ≈ 0.261 GeV, the ratio m PS =T CEP ≈ 10.37.…”

“…See also Refs. [53][54][55] for the LQCD determination of this graph. (The continuum extrapolation, however, remains elusive.)…”