Acceptance effects and background studies in the $B_{d} \rightarrow K^{*} \mu^{+}\mu^{-}$ decay at LHCb

Potential biases on the dimuon mass squared distribution and forward-backward asymmetry (FBA) in the $B_{d} \rightarrow K^{*} \mu^{+}\mu^{-}$ channel are discussed. Biases due to the offline or trigger selection of the events and due to the mismeasurement of the background distributions were studied. The major contribution to the event selection biases was found to be from the selection applied to muon candidates. A method to study this bias with data is suggested. The sensitivity obtained for the FBA zero crossing point was $\sigma_{S_{0}}$=GeV$^{2}$/c $^{4}$ for 2 fb $^{-1 }$ data when the background contribution was taken into account. Mismeasurement of the background level can lead to a bias in the FBA, and the asymmetric forward-backward background component should be estimated with an accuracy better that 50 % to prevent biases comparable to the 2 fb$^{-1 }$ statistical sensitivity. These studies were performed using an unbinned FBA analysis.