Search for the decay B0s→D∗∓π±

A search for the decay B0s→D∗∓π± is presented using a data sample corresponding to an integrated luminosity of 1.0 fb−1 of pp collisions collected by LHCb. This decay is expected to be mediated by a W-exchange diagram, with little contribution from rescattering processes, and therefore a measurement of the branching fraction will help to understand the mechanism behind related decays such as B0s→π+π− and B0s→DD−−. Systematic uncertainties are minimised by using B0→D∗∓π± as a normalisation channel. We find no evidence for a signal, and set an upper limit on the branching fraction of B(B0s→D∗∓π±)<6.1(7.8)×10−6 at 90% (95%) confidence level.