Measurement of the Bs⁰ → ϕϕ branching fraction and search for the decay B⁰ → ϕϕ

Using a dataset corresponding to an integrated luminosity of 3.0 fb ⁻¹ collected in pp collisions at centre-of-mass energies of 7 and 8 TeV, the B _s ⁰ → ϕϕ branching fraction is measured to be (formula presented.)where f _s/f _d represents the ratio of the B _s ⁰to B ⁰ production cross-sections, and the B ⁰ → ϕK ^*(892) ⁰ decay mode is used for normalization. This is the most precise measurement of this branching fraction to date, representing a factor five reduction in the statistical uncertainty compared with the previous best measurement. A search for the decay B ⁰ → ϕϕ is also made. No signal is observed, and an upper limit on the branching fraction is set as(formula presented.)at 90% confidence level. This is a factor of seven improvement compared to the previous best limit.