Evidence for the decays $B^{ 0}\rightarrow\bar{ D}^{ 0}\phi$ and $B^{ 0} \rightarrow \bar{ D}^{ *0}\phi$ is reported with a significance of 3.6$\,\sigma$ and 4.3$\,\sigma$, respectively. The analysis employs $pp$ collision data at centre-of-mass energies $\sqrt{ s}=7$, 8 and 13 TeV collected by the LHCb detector and corresponding to an integrated luminosity of 9 $\rm{ fb}^{ -1}$. The branching fractions are measured to be $\mathcal{ B}(B^{ 0}\rightarrow\bar{ D}^{ 0}\phi) = (7.7\pm2.1\pm0.7\pm0.7)\times10^{ -7}$,$\mathcal{ B}(B^{ 0} \rightarrow \bar{ D}^{ *0}\phi)=(2.2\pm0.5\pm0.2\pm0.2)\times10^{ -6}$. In these results, the first uncertainties are statistical, the second systematic, and the third is related to the branching fraction of the $B^{ 0}\rightarrow\bar{ D}^{ 0}K^{ +}K^{ -}$ decay, used for normalisation. By combining the branching fractions of the decays $B^{ 0}\rightarrow\bar{ D}^{ (*)0}\phi$ and $B^{ 0}\rightarrow\bar{ D}^{ (*)0}\omega$, the $\omega$-$\phi$ mixing angle $\delta$ is constrained to be $\tan^2\delta = (3.6\pm0.7\pm0.4)\times10^{ -3}$, where the first uncertainty is statistical and the second systematic. An updated measurement of the branching fractions of the $B^{ 0}_{ s} \rightarrow \bar{ D}^{ (*)0}\phi$ decays, which can be used to determine the CKM angle $\gamma$, leads to $\mathcal{ B}(B^{ 0}_{ s}\rightarrow\bar{ D}^{ 0}\phi)=(2.30\pm0.10 \pm 0.11\pm0.20)\times10^{ -5}$,$\mathcal{ B}(B^{ 0}_{ s}\rightarrow\bar{ D}^{ *0}\phi) =(3.17\pm0.16 \pm 0.17 \pm 0.27)\times10^{ -5}$.
Categories: hep-ex