Measurement of the absolute branching ratios for semileptonic K+- decays with the KLOE detector.

Using a sample of over 600 million → K+K− decays collected at the DAΦNE e+e− collider, we have measured with the KLOE detector the absolute branching ratios for the charged kaon semileptonic decays, K± → π0e±ν(γ) and K± → π0μ±ν(γ). The results, BR(Ke3) = 0.04965±0.00038stat±0.00037syst and BR(Kμ3) = 0.03233±0.00029stat±0.00026syst, are inclusive of radiation. Accounting for correlations, we derive the ratio Γ(Kμ3)/Γ(Ke3) = 0.6511±0.0064. Using the semileptonic form factors measured in the same experiment, we obtain |Vus f+(0)| = 0.2141 ±0.0013$.