Observation of $D_s^{**}$ states in semileptonic$B$ decays

Using 460 pb$^{-1}$ of integrated luminosity accumulated with the D\O\ detector, we have observed the semileptonic decays $B \rightarrow \mu \mu D^{**}_s$ where the different excited $D^{**}_s$ are reconstructed in the mode $D^{**}_s \rightarrow D^{*} K^0_S$. Mass peaks in the invariant mass of $D^{*} K^0_S$ are presented.