LAUSR

A measurement of the branching fraction of the decay Bs0→KS0KS0 is performed using proton–proton collision data corresponding to an integrated luminosity of 5  fb-1 collected by the LHCb experiment between 2011 and 2016. The branching fraction is determined to be B(Bs0→KS0KS0)=[8.3±1.6(stat)±0.9(syst)±0.8(norm)±0.3(fs/fd)]×10-6, where the first uncertainty is statistical, the second is systematic, and the third and fourth are due to uncertainties on the branching fraction of the normalization mode B0→ϕKS0 and the ratio of hadronization fractions fs/fd. This is the most precise measurement of this branching fraction to date. Furthermore, a measurement of the branching fraction of the decay B0→KS0KS0 is performed relative to that of the Bs0→KS0KS0 channel, and is found to be B(B0→KS0KS0)B(Bs0→KS0KS0)=[7.5±3.1(stat)±0.5(syst)±0.3(fs/fd)]×10-2.