Study of branching ratio and polarization fraction in neutral B meson decays to negative rho meson positive kaon resonance

We present the preliminary results on the search for B 0 → rho-K*+. The data sample comprises 122.7 million BB¯ pairs in the e+e- annihilation through the Upsilon(4S) resonance collected during 1999--2003 with the BABAR detector at the PEP-II asymmetric-energy collider at Stanford Linear Accelerator Center (SLAC). We obtain an upper limit of the branching ratio at 90% confidence level as B (B0 → rho- K*+) < 17.2 x 10-6 . The fitted result on the polarization fraction shows no evidence that the decay is longitudinally dominated as predicted by various theoretical models.