We present the results of the physical point simulation in $2+1$ flavor lattice QCD with the nonperturbatively $O(a)$-improved Wilson quark action and the Iwasaki gauge action at $\beta =1.9$ on a ${32}^3\times 64$ lattice. The physical quark masses together with the lattice spacing is determined with $m_{\pi }$, $m_K$ and $m_{\Omega }$ as physical inputs. There are two key algorithmic ingredients to make possible the direct simulation at the physical point: One is the mass-preconditioned domain-decomposed HMC algorithm to reduce the computational cost. The other is the reweighting technique to adjust the hopping parameters exactly to the physical point. The physics results include the hadron spectrum, the quark masses and the pseudoscalar meson decay constants. The renormalization factors are nonperturbatively evaluated with the Schrödinger functional method. The results are compared with the previous ones obtained by the chiral extrapolation method.

• Received 13 November 2009

DOI:https://doi.org/10.1103/PhysRevD.81.074503