Selection of $B^{0}_{s} \to D^{-}_{s}\mu^{+}\nu_{\mu}$ events in LHCb

The semileptonic decay B_s->D_smunu can be used to measure several important parameters of the B_s meson system: the mass difference Deltam_s, the decay width difference DeltaGamma_s and the CP asymmetry in B_s mixing. It is also a control channel to calibrate the flavour tagging procedure. This note briefly describes the selection of B_s->D_smunu with the LHCb experiment. We expect about one million of signal events in 2 fb^-1 of data with a background to signal ratio B/S = 0.36.