Pseudoscalar decay constants in the relativized quark model and measuring the CKM matrix elements

We have calculated the pseudoscalar decay constants using the relativized quark model. We find fD240±20 MeV, fDₛ290±20 MeV, fB155±15 MeV, fBₛ210±20 MeV, and fBc410±40 MeV where the "errors" are our estimates of the reliability of the results. We used these values to study the Cabibbo-Kobayashi-Maskawa matrix elements. In particular, we combined our theoretical estimate of fB with the ARGUS/CLEO result for B⁰-B̄⁰ mixing to study the relation between |Vtd| and the t-quark mass. Recent measurements of |Vbc| and |Vbu| constrain mₜ70 GeV.