KLOE extraction of Vus from kaon decays and lifetimes

Abstract

The most precise determination of Vus comes from semileptonic kaon decays. The KLOE experiment at DA\PhiNE the Frascati \phi-factory, has measured all the exeperimental inputs to Vus for both neutral and charged kaons. Preliminary results for BR(K^\pm\to\pi^0 e^\pm\nu) and BR(K^\pm\to\pi^0 \mu^\pm\nu), and for \tau_\pm are presented, together with measurements of the K_Le3 and K_L\mu3 decay BR, the K_Se3 decay BR and the K_L lifetime \tau_L. From our results for the 5 braching ratios and \tau_L we find Vus=0.2258\pm0.0022. We have also measured the fully inclusive K^+\mu2(\gamma) absolute branching ratio for which we obtain BR(K^+\to\mu\nu(\gamma))=0.6366\pm0.0017. Combining this value with recent lattice results for f_K/f_\pi gives Vus=0.2223\pm0.0026.