Study of rare and suppressed processes in B meson decays with ATLAS.

Evidence for New Physics signatures is searched in weak decays that are naturally suppressed in the Standard Model, such us processes with flavor-changing neutral-currents. The presentation will include results on the following topics: a) The angular distribution parameters A_FB and F_L describing the decay of Bd into K*mu+mu- (K+pi-mu+mu-) . The accuracy obtained from data collected in 2011 is comparable to the best previous measurement in the region of large q^2(mu+mu-). b) The study of the rare decay Bs (B0) -> mu+mu- is discussed, including the presentation of the new limit for Bs from data collected in 2011, and the prospect for results based on the large sample collected in 2012.