Physics Department Colloquium

The phenomenon of CP violation, the propensity of nature to treat matter and antimatter differently, is one of the necessary conditions to produce the observed baryon-antibaryon asymmetry of the universe. In the Standard Model of particle physics, the Kobayashi-Maskawa (KM) mechanism explains CP violation as arising from a single phase in the weak-interaction Lagrangian describing transitions between different quark flavors. This picture has been dramatically confirmed by the B-Factory experiments (BaBar in the US, and Belle in Japan) through precision measurements of the CP-violating parameter sin(2*beta), and more recently, through observation of a significant difference between the decay rates for B^0 ---> K^+ pi^- and the CP-conjugate decay B^0 bar---> K^- pi^+ . At the same time, it is known that the KM mechanism by itself is insufficient to explain the baryon asymmetry, while New Physics models predict additional CP-violating phases that could show observable effects at the B Factories. The study of CP violation in the B system therefore offers a unique window on new phenomena in the remaining years before start-up of the Large Hadron Collider at CERN (expected late 2007). I will summarize recent progress in the understanding of CP violation, and possible avenues in the search for signs of physics beyond the Standard Model.