Determination of B*B pi coupling in unquenched QCD

TL;DR

This paper calculates the B*B pi coupling in unquenched QCD using lattice simulations with improved techniques, achieving high statistical accuracy to inform chiral effective theories involving heavy-light mesons.

Contribution

The study introduces a precise lattice QCD computation of the B*B pi coupling with unquenched simulations and advanced statistical methods, improving accuracy over previous quenched results.

Findings

Achieved 1-2% statistical accuracy in coupling measurement.

Successfully applied all-to-all propagator technique to unquenched lattices.

Provided data to constrain chiral behavior of heavy-light meson parameters.

Abstract

The $B^* B\pi$ coupling is a fundamental parameter of chiral effective Lagrangian with heavy-light mesons and can constrain the chiral behavior of $f_B$, $B_B$ and the $B\to \pi l \nu$ form factor in the soft pion limit. We compute the $B^* B \pi $ coupling with the static heavy quark and the $O(a)$-improved Wilson light quark. Simulations are carried out with $n_f=2$ unquenched $12^3\times 24$ lattices at $\beta=1.80$ and $16^3\times 32$ lattices at $\beta=1.95$ generated by CP-PACS collaboration. To improve the statistical accuracy, we employ the all-to-all propagator technique and the static quark action with smeared temporal link variables following the quenched study by Negishi {\it et al.}. These methods successfully work also on unquenched lattices, and determine the $B^*B\pi$ coupling with 1--2% statistical accuracy on each lattice spacing.