Search for the decay of a B0 or B¯0 meson to K¯*0K0 or K*0K¯0

We present a search for the decay of a B0 or B̅ 0 meson to a K̅ *0K0 or K*0K̅ 0 final state, using a sample of approximately 232×106 BB̅ events collected with the BABAR detector at the PEP-II asymmetric energy e+e- collider at SLAC. The measured branching fraction is B(B0→K̅ *0K0)+B(B0→K*0K̅ 0)=(0.2-0.8-0.3+0.9+0.1)×10-6. We obtain the following upper limit for the branching fraction at 90% confidence level: B(B0→K̅ *0K0)+B(B0→K*0K̅ 0)<1.9×10-6. We use our result to constrain the standard model prediction for the deviation of the CP asymmetry in B0→ϕK0 from sin⁡2β.