Charmless B decays in modes with similar tree and penguin contributions

Charmless B decays are dominated by contributions from the short distance amplitudes from tree level and penguin loop-level amplitudes. The Tree contribution presents a weak phase γ. The interference between these two amplitudes can generate a CP asymmetry depending on the relative contribution of each amplitude. In multi-body charmless B decays, these relative contributions can change along the phase space, given a non isotropic distribution of CP asymmetries in the Dalitz plot. Two recent LHCb analyses involving charmless multi-body B decays are discussed: the observation of CP asymmetries in the phase space of the three-body decays B± → π±π+π- and B± → π±K+K-; and the angular analysis of the B0 → φK*(892)0 decay. (author)