## Nucleon axial charge and pion decay constant from two-flavor lattice QCD    [PDF]

R. Horsley, Y. Nakamura, A. Nobile, P. E. L. Rakow, G. Schierholz, J. M. Zanotti
The axial charge of the nucleon $g_A$ and the pion decay constant $f_\pi$ 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 $m_\pi=130\,{MeV}$. The volume dependence of $g_A$ and $f_\pi$ can be understood quantitatively in terms of lattice ChPT. At the physical pion mass we find $g_A=1.24(4)$ and $f_\pi=89\pm 1.1\pm 1.8\, {MeV}$, using $r_0=0.50(1)\,{fm}$ to set the scale, in good agreement with experiment. As a by-product we obtain the low-energy constant $\bar{l}_4=4.2(1)$.
View original: http://arxiv.org/abs/1302.2233