Measurement of the Ratios of Branching Fractions B(Bs0→Ds-π+)/B(B0→D-π+) and B(B+→D¯0π+)/B(B0→D-π+)

We report an observation of the decay B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +} in pp collisions at {radical}(s)=1.96 TeV using 115 pb{sup -1} of data collected by the CDF II detector at the Fermilab Tevatron. We observe 83{+-}11(stat) B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +} candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at a pp collider. We present the first measurement of the relative branching fraction B(B{sub s}{sup 0}{yields}D{sub s}{sup -}{pi}{sup +})/B(B{sup 0}{yields}D{sup -}{pi}{sup +})=1.32{+-}0.18(stat){+-}0.38(syst). We also measure B(B{sup +}{yields}D{sup 0}{pi}{sup +})/B(B{sup 0}{yields}D{sup -}{pi}{sup +})=1.97{+-}0.10(stat){+-}0.21(syst), which is consistent with previous measurements.