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Measurement of the branching ratio of the decay KL -> pi e nu and extraction of the CKM parameter |Vus|

NA48 collaboration
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Abstract

We present a new measurement of the branching ratio R of the decay KL -> pi e nu (Ke3), relative to all charged KL decays with two tracks, based on data taken with the NA48 detector at the CERN SPS. We measure R = 0.4978 +- 0.0035. From this we derive the Ke3 branching fraction and the weak coupling parameter |Vus| in the CKM matrix. We obtain |Vus|f+(0) = 0.2146 +- 0.0016, where f+(0) is the vector form factor in the Ke3 decay.

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NA48 collaboration. 2004-10-20. Measurement of the branching ratio of the decay KL -> pi e nu and extraction of the CKM parameter |Vus|. https://doi.org/10.1016/j.physletb.2004.09.056

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