A cut-based selection for $Bd \to K^{*0} \mu+ \mu-$ at LHCb

The decay $Bd \to K^{*0} \mu+ \mu-$ proceeds via a flavour changing neutral current and is sensitive to new physics. This note describes a cut-based selection for this decay, developed with the latest generation of simulated data, which includes an improved description of the detector material. The background was studied with a sample of events in which b\overline{b} quarks generated in the primary interaction gave rise to two muons. The total selection efficiency is estimated to be (0.71 +- 0.02)%, assuming a trigger efficiency of 87%. The signal yield is then expected to be 4200 -1000 +1100 events per 2fb^{-1} integrated luminosity, with a residual background of 200 +- 140 events, giving a background-to-signal ratio 0.05 +- 0.04. The residual background consists of candidates in which three particles originating from a single B hadron decay are combined with a particle selected from another B decay. A selection suitable for preliminary event filtering or 'stripping' is also outlined.