Search for CP violation in semileptonic Bs decays

We have performed a search for CP violation in a sample of Bs -> Ds mu X decays corresponding to $5$~fb${}^{-1}$ of proton-antiproton collisions collected by the D0 detector in Run~II at the Fermilab Tevatron Collider. New physics in $B_s^0$ mixing could contribute a significant CP violating weak phase, which would be observed as a difference in the decay-time distribution for $B_s^0\to \bar{B}_s^0$oscillatedstatesversusthatfor$\bar{B}s^0\to {B}s^0$. A fit to the decay-time distributions of the $B_s^0\mathrm{/}{\bar{B}}_s^0$ candidates yields the flavor-specific asymmetry $a{fs}^{s}=[-1.7\pm 9.1$(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})$^{+1.4}{-1.5}$(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$] \times 10^{-3}$, which excludes CP violation due to new physics within the experimental sensitivity.