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Measurements of Charged Kaon Semileptonic Decay Branching Fractions K^+- -> pi^0 mu^+- nu and K+- -> pi^0 e^+- nu and Their Ratio

J. R. Batley·NA48/2 collaboration
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Abstract

Measured ratios of decay rates for Ke3/K2π, K\mu3/K2πand K\mu3/Ke3 are presented. These measurements are based on K^+- decays collected in a dedicated run in 2003 by the NA48/2 experiment at CERN. The results obtained are Ke3/K2π= 0.2470 +/- 0.0009 (stat) +/- 0.0004 (syst) and K\mu3/K2π= 0.1637 +/- 0.0006 (stat) +/- 0.0003 (syst). Using the PDG average for the K^+- -> π^+-π^0 normalisation mode, both values are found to be larger than the current values given by the Particle Data Book and lead to a larger magnitude of the |V_{us}| CKM element than previously accepted. When combined with the latest Particle Data Book value of |V_{ud}|, the result is in agreement with unitarity of the CKM matrix. In addition, a new measured value of K\mu3/Ke3 = 0.663 +/- 0.003(stat) +/- 0.001(syst) is compared to the semi-empirical predictions based on the latest form factor measurements.

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J. R. Batley, NA48/2 collaboration. 2007-05-21. Measurements of Charged Kaon Semileptonic Decay Branching Fractions K^+- -> pi^0 mu^+- nu and K+- -> pi^0 e^+- nu and Their Ratio. https://doi.org/10.1140/epjc%2Fs10052-007-0253-3%2010.1140%2Fepjc%2Fs10052-007-0454-9

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