Measurement of the Branching Fraction for ${B}_{s} \rightarrow {D}_{s1}^{\pm}(2536) \mu \nu {X} \:$ at D0

The state ${B}^0_{s} \rightarrow {D}_{s1}^{\pm}(2536) \mu \nu {X} \:$ has been observed at D0 through the decay channel ${D}_{s1}^ {\pm}(2536) \rightarrow {D}^{* \pm} K^0_S \:$ with $D^{*+}$ $\rightarrow$ ${D^0}$ $\pi^+$, ${D^0}$ $\rightarrow K^- \pi^+$ and $K_S^0 \rightarrow \pi^+ \pi^-$. The branching fraction for this $B^0_s$ semileptonic decay to an orbitally excited $D_s$ state is measured for the first time and the ${D}_{s1}^{\pm}(2536)\:$ mass peak is presented with a signal significance of greater than 5.0 sigma in approximately 1.3 fb$^{-1}$ of data from the D0 detector.