Calculation of the heavy-hadron axial couplings g_1, g_2, and g_3 using lattice QCD

TL;DR

This paper reports on a lattice QCD calculation of heavy-hadron axial couplings g_1, g_2, and g_3, which are essential for understanding interactions involving heavy baryons and pions, with detailed analysis and additional predictions.

Contribution

The paper provides a detailed lattice QCD calculation of heavy-hadron axial couplings and discusses the convergence of chiral perturbation theory at various pion masses, including new numerical results and decay predictions.

Findings

Numerical values for g_1, g_2, g_3 obtained from lattice QCD.

Confirmation of chiral perturbation theory convergence up to 400 MeV pion mass.

Predictions for decay widths of charm and bottom baryons.

Abstract

In a recent letter [Phys. Rev. Lett. 108, 172003 (2012), arXiv:1109.2480] 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 (HH$\chi$PT) and are related to the $B^*B\pi$, $\Sigma_b^*\Sigma_b\pi$, and $\Sigma_b^{(*)}\Lambda_b\pi$ 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 HH$\chi$PT. 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 $SU(4|2)$ HH$\chi$PT for the axial-current matrix elements at pion masses up to about 400 MeV 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.