UC Berkeley

We present measurements of the branching fraction and fraction of longitudinal polarization for the decay B+→K̄*0K*+ with a sample of (467±5)×106 BB̄ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at the SLAC National Accelerator Laboratory. We obtain the branching fraction B(B+→K̄ *0K*+)=(1.2±0.5±0.1)×10-6 with a significance of 3.7 standard deviations including systematic uncertainties. We measure the fraction of longitudinal polarization fL=0.75-0.26+0.16±0.03. The first error quoted is statistical and the second is systematic. © 2009 The American Physical Society.