Given the 3σ deviations for nearly a decade in several measurements of the B sector (including differential BF of rare decays, angular observables and tests of lepton flavour universality; which create an interesting pattern of deviations), we deployed a novel trigger strategy to confirm these results. The strategy is based on a single displaced muon to collect interesting events, which are stored directly on tapes until there are computing resources available to process them. Since the events are not reconstructed promptly, there is no prompt reconstruction bottleneck, which permits to store huge amount of data. In this analysis we measured the Rk which is defined as BF (B->Kμμ)/BF(Β->Κee ) and is one of the most sensitive observables for lepton flavour universality tests. In the same analysis we also measured differential BF for B->Κμμ with precision that rivals the world average.
