Evidence for the decay B0→ωω and search for B0→ωφ

We describe searches for B meson decays to the charmless vector-vector final states ωωand ωφwith 471×106BB̄pairs produced in e+e- annihilation at s=10.58GeV using the BABAR detector at the PEP-II collider at the SLAC National Accelerator Laboratory. We measure the branching fraction B(B0→ωω)=(1.2$\pm$0.3-0.2+0.3)×10- 6, where the first uncertainty is statistical and the second is systematic, corresponding to a significance of 4.4 standard deviations. We also determine the upper limit B(B0→ωφ)<0.7×10-6 at 90{\%} confidence level. These measurements provide the first evidence for the decay B0→ωω, and an improvement of the upper limit for the decay B0→ωφ.