Preparations for precise measurements of rare muonic B-decays

The LHC experiments will perform sensitive tests of physics phenomena beyond the Standard Model (BSM). Decays of beauty hadrons represent an alternative approach in addition to direct BSM searches. In rare B-decay sector, ATLAS concentrates on the decays with two muons in final state. In family of semi-muonic rare decays, ATLAS prepares measurements in six decay channels of Bd , Bs and Λb . After three years, ATLAS will be able unambiguously to confirm or exclude certain classes of Minimal Super Symmetric Models (MSSM) in confrontation with SM. The strategy is to carry on the di-muon channel program up to nominal LHC luminosity. In particular, for the Bs → µµ channel, a branching fraction sensitivity up to few times 10^−10 is expected already after one year of LHC operation at a luminosity of 10^34 cm^−2 s^−1 . This precision allows excluding or confirming the SM unambiguously.