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

doi:10.1016/j.physletb.2014.03.002

paper

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

arXiv:1302.2233 · doi:10.1016/j.physletb.2014.03.002

Abstract

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 $m_π=130\,\mbox{MeV}$. 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 decreasing 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 $f_π^R=89.6(1.1)(1.8)\,\mbox{MeV}$. Both sets of results are in good agreement with experiment. As a by-product we obtain the low-energy constant $l ˉ_{4} = 4.2 (1)$ .

16 pages, 8 figures; published version (Physics Letters B)

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

Abstract

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