Study of the branching ratio and charge asymmetry for the decay K(S) -> pi e nu with the KLOE detector

Among some 400 million K(S)K(L) pairs produced in e(+)e(-) annihilations at DA Phi DNE, similar to 6500 each of K(S) -> pi(+)e(-)(v) over bar and K(S) -> pi(-)e(+)v decays have been observed with the KLOE detector. From these, the ratio Gamma(K(S) -> pi ev)/Gamma(K(S) -> pi(+)pi(-)) = (10.19 +/- 0.13) x 10(-4) is obtained, improving the accuracy on BR(K(S) -> pi ev) by a factor of four and providing the most precise test of the Delta S = Delta Q rule. From the partial width F(K(S) -> pi ev), a value for f(+)(K0) (0) x V(us) is obtained that is in agreement with unitarity of the quark-mixing matrix. The lepton charge asymmetry A(S) = (1.5 +/- 9.6(stat) 2.9(syst)) x 10(-3) is compatible with the requirements of CPT invariance. The form-factor slope agrees with recent results from semileptonic K(L) and K(+) decays. These are the first measurements of the charge asymmetry and form-factor slope for semileptonic K(S) decays. (c) 2006 Elsevier B.V. All rights reserved.