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Study of the CP asymmetry of B0 -> J/psi K0S decays in ALEPH

ALEPH Collaboration
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Abstract

The decay B0 -> J/psi K0_S is reconstructed with J/psi -> e+ e- or mu+ mu- and K0_S -> pi+ pi-. From the full ALEPH dataset at LEP1 of about 4 million hadronic Z decays, 23 candidates are selected with an estimated purity of 71%. They are used to measure the CP asymmetry of this decay, given by sin 2beta in the Standard Model, with the result sin 2beta = 0.84 +0.82-1.04 +-0.16. This is combined with existing measurements from other experiments, and increases the confidence level that CP violation has been observed in this channel to 98%.

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ALEPH Collaboration. 2000-09-27. Study of the CP asymmetry of B0 -> J/psi K0S decays in ALEPH. https://doi.org/10.1016/s0370-2693(00)01091-1

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