Direct CP violating asymmetry in B-0 -> K+pi(-) decays

We present a measurement of the direct CP violating asymmetry in the decay B-0-->K(+)pi(-) using a data sample of 227x10(6) Y(4S)-->B (B) over bar decays ollected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at SLAC. We observe a total signal yield of n(K)(-)pi(+)+n(K)(+)pi(-)=1606+/-51 decays and measure the asymmetry (n(K)(-)pi(+)-n(K)(+)pi(-))/(n(K)(-)pi(+)+n(K)(+)pi(-))=-0.133+/-0.030(s tat)+/-0.009(syst). The probability of observing such an asymmetry in the absence of direct CP violation is 1.3x10(-5), corresponding to 4.2 standard deviations.