Nucleon axial charge and pion decay constant from two-flavor lattice QCD

R. Horsley, Y. Nakamura, A. Nobile, P.E.L. Rakow, G. Schierholz, J.M. Zanotti
2014 Physics Letters B  
The axial charge of the nucleon g_A and the pion decay constant f_π are computed in two-flavor lattice QCD. The simulations are carried out on lattices of various volumes and lattice spacings. Results are reported for pion masses as low as m_π=130 MeV. Both quantities, g_A and f_π, suffer from large finite size effects, which to leading order ChEFT and ChPT turn out to be identical. By considering the naturally renormalized ratio g_A/f_π, we observe a universal behavior as a function of
more » ... ng quark mass. From extrapolating the ratio to the physical point, we find g_A^R=1.29(5)(3), using the physical value of f_π as input and r_0=0.50(1) to set the scale. In a subsequent calculation we attempt to extrapolate g_A and f_π separately to the infinite volume. Both volume and quark mass dependencies of g_A and f_π are found to be well decribed by ChEFT and ChPT. We find at the physical point g_A^R=1.24(4) and f_π^R=89.6(1.1)(1.8) MeV. Both sets of results are in good agreement with experiment. As a by-product we obtain the low-energy constant l̅_4=4.2(1).
doi:10.1016/j.physletb.2014.03.002 fatcat:oagnbi2lnncphetudkjb6uns4q