QCD crossover temperature and curvature coefficient from unbiased exponential resummation at physical quark masses in (2+1)-flavor lattice QCD

We present the first application of the unbiased exponential resummation method to the determination of the QCD pseudocritical temperature Tpc at vanishing baryon chemical potential μB. By reconstructing the finite-density baryon number susceptibility χ₂B, we define two thermal-derivative observables whose peak positions yield TpcT=160.2(4)(3) MeV and TpcC=158.1(5)(3) MeV. We also show that the pseudocritical temperature, Tpc^χ obtained from the peak of the fourth-order baryon number susceptibility χ₄B is consistent with these determinations and with previous lattice-QCD results based on Taylor expansions {Bollweg:2022Pade}. Further, we demonstrate that scaling relations {Bollweg:2022fqq} between χ₄B and the thermal derivatives of χ₂B yield mutually consistent estimates of the leading second order curvature coefficient κ₂B at the corresponding pseudocritical temperatures. A direct analysis of the μB dependence of the pseudocritical temperatures provides an independent but substantially less constrained determination of the curvature, which remains statistically consistent with the scaling-based estimates. These results demonstrate the consistency of unbiased exponential resummation with the expected scaling behavior and establish it as a complementary approach for probing the QCD crossover at small finite baryon density.