First observation of the decay Bs0→Ds-Ds+ and measurement of its branching ratio

We report the observation of the exclusive decay B-s(0)-> Ds-Ds+ at the 7.5 standard deviation level using 355 pb(-1) of data collected by the CDF II detector in p (p) over bar collisions at root s =1.96 TeV at the Fermilab Tevatron. We measure the relative branching ratio B(B-s(0)-> Ds-Ds+)/B(B-0 -> D-Ds+)=1.44(-0.44)(+0.48). Using the world average value for B(B-0 -> D-Ds+), we find B(B-s(0)-> Ds-Ds+)=(9.4(-4.2)(+4.4))x10(-3). This provides a lower bound Delta Gamma(CP)(s)/Gamma(s)>= 2B(B-s(0)-> Ds-Ds+)> 1.2x10(-2) at 95% C.L.