Bound on the Ratio of Decay Amplitudes for B̅ 0→J/ψK*0 and B0→J/ψK*0

We have measured the time-dependent decay rate for the process B→J/ψK*0(892) in a sample of about 88×10^6 Υ(4S)→BB̅ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. In this sample we study flavor-tagged events in which one neutral B meson is reconstructed in the J/ψK*0 or J/ψK̅ *0 final state. We measure the coefficients of the cosine and sine terms in the time-dependent asymmetries for J/ψK*0 and J/ψK̅ *0, find them to be consistent with the standard model expectations, and set upper limits at 90% confidence level (C.L.) on the decay amplitude ratios |A(B̅ 0→J/ψK*0)|/|A(B0→J/ψK*0)|<0.26 and |A(B0→J/ψK̅ *0)|/|A(B̅ 0→J/ψK̅ *0)|<0.32. For a single ratio of wrong-flavor to favored amplitudes for B0 and B̅ 0 combined, we obtain an upper limit of 0.25 at 90% C.L.