Nonperturbatively improved heavy-light mesons: Masses and decay constants

Abstract

We present a study of the heavy-light spectrum and of the D- and B-meson decay constants. The results were obtained in the quenched approximation, by using the nonperturbatively improved clover lattice action at $\ensuremath{\beta}=6.2,$ with a sample of $100$ configurations, on a ${24}^{3}\ifmmode\times\else\texttimes\fi{}64$ lattice. After a careful analysis of the systematic errors present in the extraction of the physical results, by assuming quite conservative discretization errors, we find ${f}_{{D}_{s}}=231\ifmmode\pm\else\textpm\fi{}{12}_{\ensuremath{-}1}^{+8} \mathrm{MeV},$ ${f}_{D}=211\ifmmode\pm\else\textpm\fi{}{14}_{\ensuremath{-}12}^{+2} \mathrm{MeV},$ ${f}_{{D}_{s}}{/f}_{D}=1.10(2),$ ${f}_{{B}_{s}}=204\ifmmode\pm\else\textpm\fi{}{16}_{\ensuremath{-}0}^{+36} \mathrm{MeV},$ ${f}_{B}=179\ifmmode\pm\else\textpm\fi{}{18}_{\ensuremath{-}9}^{+34} \mathrm{MeV},$ ${f}_{{B}_{s}}{/f}_{B}{=1.14(3)}_{\ensuremath{-}1}^{+1}.$ Our results, which have smaller discretization errors than many previous estimates at fixed value of the lattice spacing a, support a large value of ${f}_{B}$ in the quenched approximation.