Measurement of B¯0→D(*)0K¯(*)0 branching fractions

We present a study of the decays B̅ 0→D(*)0K̅ (*)0 using a sample of 226×106 Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We report evidence for the decay of B0 and B̅ 0 mesons to the D*0KS0 final state with an average branching fraction B(B˜0→D*0K˜0)≡(B(B̅ 0→D*0K̅ 0)+B(B0→D*0K0))/2=(3.6±1.2±0.3)×10-5. Similarly, we measure B(B˜0→D0K˜0)≡(B(B̅ 0→D0K̅ 0)+B(B0→D0K0))/2=(5.3±0.7±0.3)×10-5 for the D0KS0 final state. We measure B(B̅ 0→D0K̅ *0)=(4.0±0.7±0.3)×10-5 and set a 90% confidence level upper limit B(B̅ 0→D̅ 0K̅ *0)<1.1×10-5. We determine the upper limit for the decay amplitude ratio |A(B̅ 0→D̅ 0K̅ *0)/A(B̅ 0→D0K̅ *0)| to be less than 0.4 at the 90% confidence level.