Search for B+ meson decay to a1+ K*0

We present a search for the decay $B^{+}\to a_1^{+}(1260)K^{\ast 0}(892)$. The data, collected with the \mbox{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the SLAC National Accelerator Laboratory, represent 465 million $B\bar{B}$ pairs produced in $e^{+}{e}^{-}$ annihilation at the energy of the $\mathrm{{\rm Y}}(4s)$. We find no significant signal and set an upper limit at 90%\ confidence level on the product of branching fractions {\cal B}(B^+ \rightarrow a_1^+(1260) K^{*0}(892)) \times {\cal B}(a_1^+(1260) \rightarrow \pi^+ \pi^- \pi^+) of $1.8 \times 10^{-6}$.