Measurement of the absolute branching ratios for semileptonic K± decays with the KLOE detector

Using a sample of over 600 million φ → K+K − decays collected at the DANE 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 ± → π0� ±ν(γ). The results, BR(Ke3) = 0.04965 ± 0.00038stat ± 0.00037syst and BR(K� 3) = 0.03233 ± 0.00029stat ± 0.00026syst, are inclusive of radiation. Accounting for correlations, we derive the ratio ( K� 3)/( Ke3) = 0.6511 ± 0.0064. Using the semileptonic form factors measured in the same experiment, we obtain |Vus f+(0)| = 0.2141 ± 0.0013.