Flavor physics: precision as an avenue to discovery

The present manuscript describes work pursued in the years 2008-2013 on improving the Standard-Model prediction of selected flavor-physics observables. The latter include: (1) ' K , that quantifies indirect CP violation in the K 0 ≠K 0 system and (2) the very rare decay B s ae µµ, recently measured at the LHC. Concerning point (1), the manuscript describes our reappraisal of the long-distance contributions to ' K (refs. [1-3]), that have permitted to unveil a potential tension between CP violation in the K 0-and in the B d-system. Concerning point (2), the manuscript gives a detailed account of various systematic e ects, pointed out in ref. [4] and a ecting the Standard-Model B s ae µµ decay rate at the level of 10%-hence large enough to be potentially misinterpreted as non-standard physics, if not properly included. The manuscript further describes the multifaceted importance of the B d,s ae µµ decays as new-physics probes, for instance how they compare with Z-peak observables at LEP, following the e ective-theory approach of ref. [5]. Both cases (1) and (2) o er clear examples in which the pursuit of precision in Standard-Model predictions o ered potential avenues to discovery. Finally, the manuscript describes the impact of the above results on the literature, and what is the further progress to be expected on these and related observables