Observation of CP violation in the $B^0$ system

Abstract

The BABAR detector, operating at energies near the ${\rm Y}(4S)$ resonance at the PEP-II asymmetric $B$ Factory at SLAC, has collected a sample of 32 million $B\bar{B}$ pairs by May 2001. A study of time-dependent CP-violating asymmetries in events where one neutral $B$ meson is fully reconstructed in a final state containing charmonium has resulted in the measurement $\sin 2\beta =0.59\pm 0.14(\mathrm{stat})\pm 0.05(\mathrm{syst})$, which establishes CP violation in the $B^0$ meson system at the 4$\sigma$ level. $B$ lifetime and mixing measurements from a sub-sample of 23 million $B\bar{B}$ pairs are also presented.

11 pages, 5 figures, contributed to the Proceedings of the International Europhysics Conference on HEP (HEP2001)