PACS-CS results for 2+1 flavor lattice QCD simulation on and off the physical point

TL;DR

This paper reports on a comprehensive lattice QCD simulation at the physical point, analyzing meson and baryon masses using chiral perturbation theories, and compares direct simulation results with extrapolated estimates.

Contribution

It presents the first direct 2+1 flavor lattice QCD simulation at the physical point with detailed chiral analysis and comparison to extrapolated results.

Findings

Successful simulation at the physical point with light quark masses as low as 3 MeV.

Convergence analysis of SU(2) and SU(3) chiral expansions up to NLO.

Demonstrated the importance of direct simulation over extrapolation methods.

Abstract

We report on the PACS-CS project focusing on a direct simulation of 2+1 flavor QCD on the physical point and chiral analysis of meson and baryon masses off the physical point with both the SU(2) and SU(3) chiral perturbation theories. Configurations are generated with the O(a)-improved Wilson quark action and the Iwasaki gauge action. The up-down quark is simulated by employing the DDHMC algorithm with several improvements and the UV-filtered PHMC algorithm is implemented for the strange quark. We investigate the convergence behaviors of the SU(2) and SU(3) chiral expansions up to NLO for the pseudoscalar meson sector, where the up-down quark mass ranges from 3 MeV to 24 MeV and the strange quark mass is chosen around the physical value. The fit results for the low energy constants are compared with those recently obtained by other groups. We also discuss the importance of the direct simulation at the physical point by comparing the physical quantities measured on the physical point with those estimated by the extrapolation method.