CP Violation in B mesons

Symmetries and their conservation laws play a fundamental role in Physics. Among them, the discrete symmetries corresponding to charge (C), parity (P ), and time (T ) transformations are extensively used in the theory of the elementary particles and their interactions (so called Standard Model (SM)) to give the basis of the fundamental physical description of nature. Eventual discoveries of violations of these symmetries become a crucial test for our understanding of the nature. It was assumed that the three discrete symmetries were not violated until 1956 when it was found that P is violated in the weak interaction. Soon it was understood that also the C is violated in the weak interaction. At that time these two violated symmetries were replaced by their combination, CP , which was considered a new fundamental symmetry. In 1964 also the CP was found violated in the case of the neutral K meson system. Since that year there were many achievements in theories and experiments in order to explain this symmetry violation. In the last five years the main contribution comes from the discovery of the CP violation in B meson system. In this note we will describe briefly how the CP violation is described in the SM and the main experimental results obtained in the B mesons system. Contributed to the Proceedings of the XLV International Winter Meeting on Nuclear Physics, 1/14/2007—1/21/2007, Bormio, Italy. Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309 Work supported in part by Department of Energy contract DE-AC02-76SF00515.