Search for b -> u transitions in B-0 -> (DK)-K-0*(0) decays

We present a study of the decays B-0 -> (DK)-K-0*(0) and B-0 -> (D) over bar K-0*(0) and K*(0) -> K+pi(-). The D-0 and the (D) over bar (0) mesons are reconstructed in the final states f = K+pi(-), K+pi(-)pi(0), K+pi(-)pi(+)pi(-), and their charge conjugates. Using a sample of 465 x 10(6) B (B) over bar pairs collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at SLAC, we measure the ratio R-ADS = [Gamma((B) over bar -> [f] (K) over bar (0)) + Gamma(B-0 -> [(f) over bar K-D*(0))]/[Gamma((B) over bar (0) -> [(f) over bar (D)(K)over bar>*(0))] + Gamma(B-0 -> [f](D)K*(0))] for the three final states. We do not find significant evidence for a signal and set the following limits at 95% probability: R-ADS (K pi) < 0.244, R-ADS (K pi pi(0)) < 0.181, and R-ADs (K pi pi pi)<0.391. From the combination of these three results, we find that the ratio r(S) between the b -> u and the b -> c amplitudes lies in the range [0.07,0.41] at 95% probability.