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Phys. Rev. Lett. 87, 091801 (2001) [8 pages]

Observation of CP Violation in the B0 Meson System

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B. Aubert et al. (BABAR Collaboration)
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Received 5 July 2001; published 14 August 2001

We present an updated measurement of time-dependent CP-violating asymmetries in neutral B decays with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. This result uses an additional sample of ϒ(4S) decays collected in 2001, bringing the data available to 32×106 BB̅ pairs. We select events in which one neutral B meson is fully reconstructed in a final state containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the standard model is proportional to sin2β, is derived from the decay time distributions in such events. The result sin2β = 0.59±0.14(stat)±0.05(syst) establishes CP violation in the B0 meson system. We also determine |λ| = 0.93±0.09(stat)±0.03(syst), consistent with no direct CP violation.

© 2001 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.87.091801
DOI:
10.1103/PhysRevLett.87.091801
PACS:
13.25.Hw, 11.30.Er, 12.15.Hh