Measurement Of The Branching Fraction Br B0s U2192 Dsds Using The D0 Detector At Fermilab

This thesis describes a measurement of the branching fraction Br (B0s → Ds*Ds*) made using a data sample collected from proton-antiproton collisions at a centre-of-mass energy of 1.96 TeV, corresponding to approximately 1.3 fb-1 of integrated luminosity collected in 2002--2006 by the D0 detector at the Fermilab Tevatron Collider. One D*s meson was partially reconstructed in the decay Ds → ??v, and the other D*s meson was identified using the decay Ds → ?? where no attempt was made to distinguish Ds and D*s states. The resulting measurement is Br (B0s → Ds*Ds*) = 0.039+0.019-0.017(stat) +0.016-0.015(syst). This was subsequently used to estimate the width difference ??CPs in the B0s-$ar{B}$0s system: ??CPs/?s = 0.079+0.038-0.035(stat)+0.031-0.030(syst), and is currently one of the most precise estimates of this quantity and consistent with the Standard Model.