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

We search for B-->(D) over tilde K-0(-) and B-->(D) over tilde K-*0(-) and charge conjugates. Here the symbol D-0 indicates decay of a D-0 or (D) over bar (0) into K(+)pi(-), while the symbol (D) over tilde (*0) indicates decay of a D-*0 or (D) over bar (*0) to D(0)pi(0) or D(0)gamma. These final states can be reached through the b -> c transition B--> (DK-)-K-(*)0 followed by the doubly Cabibbo-Kobayashi-Maskawa (CKM)-suppressed D-0-> K(+)pi(-), or the b -> u transition B-->(D) over bar K-(*)0(-) followed by the CKM-favored (D) over bar (0)-> K(+)pi(-). The interference of these two amplitudes is sensitive to the angle gamma of the unitarity triangle. Our results are based on 232x10(6) Upsilon(4S)-> B (B) over bar decays collected with the BABAR detector at SLAC. We find no significant evidence for these decays. We set a limit r(B)equivalent to vertical bar A(B-->(D) over bar K-0(-))/A(B--> (DK-)-K-0)vertical bar < 0.23 at 90% C.L. using the most conservative assumptions on the values of the CKM angle gamma and the strong phases in the B and D decay amplitudes. In the case of the D-* we set a 90% C.L. limit r(B)(*2)equivalent to A(B-->(D) over bar K-*0(-))/A(B--> (DK-)-K-*0)(2)<(0.16)(2) which is independent of assumptions on gamma and strong phases.