Calculation of the heavy-hadron axial couplings g ₁, g ₂, and g ₃ using lattice QCD

In a recent letter we have reported on a lattice QCD calculation of the heavy-hadron axial couplings g ₁, g ₂, and g ₃. These quantities are low-energy constants of heavy-hadron chiral perturbation theory (HHχPT) and are related to the B ^*Bπ, Σb*Σ _bπ, and Σb(*) Λ _bπ couplings. In the following, we discuss important details of the calculation and give further results. To determine the axial couplings, we explicitly match the matrix elements of the axial current in QCD with the corresponding matrix elements in HHχPT. We construct the ratios of correlation functions used to calculate the matrix elements in lattice QCD, and study the contributions from excited states. We present the complete numerical results and discuss the data analysis in depth. In particular, we demonstrate the convergence of SU(4|2) HHχPT for the axial-current matrix elements at pion masses up to about 400MeV and show the impact of the nonanalytic loop contributions. Finally, we present additional predictions for strong and radiative decay widths of charm and bottom baryons.