Decay Constants of Heavy Meson of $0^-$ State in Relativistic Salpeter Method

The decay constants of pseudoscalar heavy mesons of $0^-$ state are computed by means of the relativistic (instantaneous) Salpeter equation. We solved the full Salpeter equation without making any further approximation, such as ignoring the small component wave function. Therefore, our results for the decay constants include the complete relativistic contributions from the light and the heavy quarks. We obtain $F_{D_s} \approx 248 \pm 27 $, $F_{D} \approx 230 \pm 25 (D^0,D^\pm)$, $F_{B_s} \approx 216 \pm 32 $, $F_{B} \approx 196 \pm 29 (B^0,B^\pm)$, $F_{B_c} \approx 322 \pm 42 $ and $F_{η_c} \approx 292 \pm 25 $ MeV.