Measurement of the branching fraction and charge asymmetry for the decay Ks->pi e nu with the KLOE detector

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  • 13 January 2006
Abstract
Among some 400 million KsKl pairs produced in e+e- annihilations at DAFNE, about 6500 each of Ks->pi+e-nubar and Ks->pi-e+nu decays have been observed with the KLOE detector. From these, BR(Ks->pienu)=(7.046+-0.091)10-4 is obtained, improving the accuracy on the BR by a factor of four and providing the most precise test of the DeltaS=DeltaQ rule. From the partial width Gamma(Ks->pienu), f+(K0)Vus=0.2162+-0.0014 is obtained, in good agreement with unitarity of the quark-mixing matrix. The lepton charge asymmetry is AS=(1.5+-10)10-3, which is compatible with the corresponding asymmetry from semileptonic Kl decays as expected from CPT invariance. The form-factor slope in the linear approximation is found to agree with recent measurements from semileptonic Kl and K+ decays. These are the first measurements of the charge asymmetry and form-factor slope for semileptonic Ks decays.

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