Measurement Of The Branching Fraction Bs Dsds Using The D0 Detector At Fermilab

This thesis describes a measurement of the branching fraction Br(B°{sub s} → D{sup (*)}{sub s} D{sup (*)}{sub s}) 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{sup (*)}{sub s} meson was partially reconstructed in the decay D{sub s} → [phi][mu][nu], and the other D{sup (*)}{sub s} meson was identified using the decay D{sub s} → [phi][pi] where no attempt was made to distinguish D{sub s} and D{sup *}{sub s} states. The resulting measurement is Br(B°{sub s} → D{sup (*)}{sub s} D{sup (*)}{sub s}) = 0.039{sup +0.019}{sub -0.017}(stat){sup +0.016}{sub -0.015}(syst). This was subsequently used to estimate the width difference [Delta][Gamma]{sup CP}{sub s} in the B°{sub s}-{anti B}°{sub s} system: [Delta][Gamma]{sup CP}{sub s}/[Gamma]{sub s} = 0.079{sup +0.038}{sub -0.035}(stat){sup +0.031}{sub 0.030}(syst), and is currently one of the most precise estimates of this quantity and consistent with the Standard Model.