The absolute branching fractions for the decays D{sub s}− → l−{bar?}{sub l} (l = e,?, or?) are measured using a data sample corresponding to an integrated luminosity of 521 fb−1 collected at center of mass energies near 10.58 GeV with the BABAR detector at the PEP-II ee− collider at SLAC. The number of D{sub s}− mesons is determined by reconstructing the recoiling system DKX? in events of the type e+e−DKXD*{sub s}−, where D*{sub s}− → D{sub s}−? and X represents additional pions from fragmentation. The D{sub s}− → l°{nu}{sub {ell}} events are detected by full or partial reconstruction of the recoiling system DKX?{ell}. The branching fraction measurements are combined to determine the D{sub s}− decay constant f{sub D{sub s}} = (258.6 ± 6.4 ± 7.5) MeV, where the first uncertainty is statistical and the second is systematic.

The authors measure the absolute branching fraction for D{sup 0} {yields} K{sup -} {pi}{sup +} using partial reconstruction of {bar B}{sup 0} {yields} D*{sup +} X {ell}{sup -} {bar {nu}}{sub {ell}} decays. Only the charged lepton and the soft pion from the decay D*{sup +} {yields} D{sup 0} {pi}{sup +} are used. Based on a data sample of 230 million B{bar B} pairs collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, they obtain {Beta}(D{sup 0} {yields} K{sup -} {pi}{sup +}) = (4.025 {+-} 0.038 {+-} 0.098)%, where the first error is statistical and the second error is systematic.

Decays of the type B 2!D{sup (*)} {bar D}(*) can be used to provide a measurement of the parameter sin2[beta] of the Unitarity Triangle that is complementary to the measurement derived from the mode B° 2!K{sub S}°. In this document we report a measurement of the branching fraction for the decay B° 2!D*D*− with the BABAR detector. With data corresponding to an integrated luminosity of 20.7 fb−1 collected at the [Upsilon](4S) resonance during 1999-2000, we have reconstructed 38 candidate signal events in the mode B° 2!D*D*− with an estimated background of 6.2 ± 0.5 events. From these events, we determine the branching fraction to be [Beta](B° 2!D*+D*−) = (8.0 ± 1.6(stat) ± 1.2(syst)) x 10−4 (preliminary). The measured fraction of the component with odd CP parity is 0.27± 0.17(stat) ± 0.02(syst).