Observation of CP violation in the B° meson system

B Aubert, Paul Bright-Thomas, Theresa Harrison, Christopher Hawkes, David Knowles, Stephen O'Neale, Richard Penny, Alan Watson, Nigel Watson

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508 Citations (Scopus)


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 Upsilon(4S) decays collected in 2001, bringing the data available to 32 x 10(6) BB macro 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 sin2 beta, is derived from the decay time distributions in such events. The result sin2 beta = 0.59+/-0.14(stat)+/-0.05(syst) establishes CP violation in the B(0) meson system. We also determine absolute value of lambda = 0.93+/-0.09(stat)+/-0.03(syst), consistent with no direct CP violation.
Original languageEnglish
Pages (from-to)091801
Number of pages1
JournalPhysical Review Letters
Issue number9
Early online date1 Aug 2001
Publication statusPublished - 1 Aug 2001


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