The paper advocates the use of a statistical tool dedicated to the exploration of data samples populated by several sources of events. This new technique, called s Plot, is able to unfold the contributions of the different sources to the distribution of a data sample in a given variable. The s Plot tool applies in the context of a Likelihood fit which is performed on the data sample to determine the yields of the various sources.

The Standard Model constraints on α which can be derived from the B → ππ decays are revisited in some depth. As experimental inputs, the B 0 → π + π − , B + → π + π 0 decays complemented by the B 0 → π 0 π 0 decays, the CP parameters S ππ and C ππ , and/or the value of α as determined by the global CKM fit are used. The constraints discussed here are model independent in the sense that they rely only on Isospin symmetry, following the Gronau-London proposal. A new bound on B 00 and the function C 00 (B 00 ) are introduced. While another bound applied to BABAR results is shown to imply that cos(2α eff ) is negative. The Grossman-Quinn bound is rediscussed. A close form expression is given for α as a function of the measurements. Various scenarii for the future of the isospin analysis are explored. To probe the Standard Model the (B 00 , C 00 ) plane is introduced.