Evidence for the decay $B^0\to \omega \omega$ and search for $B^0\to \omega \varphi$

We describe searches for $B$ meson decays to the charmless vector-vector final states $\omega \omega$ and $\omega \varphi$ with $471\times 10^{6}B\overline{B}$ pairs produced in $e^{+}{e}^{-}$ annihilation at $\sqrt{s}=10.58\mathrm{GeV}$ using the BABAR detector at the PEP-II collider at the SLAC National Accelerator Laboratory. We measure the branching fraction $\mathcal{B}(B^0\to \omega \omega )=(1.2\pm {0.3}_{-0.2}^{+0.3})\times {10}^{-6}$, 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 $\mathcal{B}(B^0\to \omega \varphi )<0.7\times {10}^{-6}$ at 90% confidence level. These measurements provide the first evidence for the decay $B^0\to \omega \omega$, and an improvement of the upper limit for the decay $B^0\to \omega \varphi$.

Figure 1

Distribution of $-2\ln \mathcal{L}(\mathcal{B})$ (normalized to the maximum likelihood ${\mathcal{L}}_0$) for $B^0\to \omega \omega$ (left) and $B^0\to \omega \varphi$ (right) decays. The dashed curves include only statistical uncertainties; the solid curves include systematic uncertainties as well.

Figure 2

Projections of $m_{\text{ES}}$ (left) and $\mathrm{\Delta }E$ (right) for a signal-enriched sample of events passing a set of dedicated selection cuts for $B^0\to \omega \omega$ (upper plots), and $B^0\to \omega \varphi$ (lower plots). The solid curve gives the total PDF (computed without the variable plotted), the dashed curve is the signal contribution, and the dot-dashed curve is the background contribution, which includes both combinatoric and peaking $B\overline{B}$ backgrounds.