New perspective in searching for axionlike particles from flavor physics

We propose new perspective in searching for axionlike particles (ALPs) from quark and lepton flavor physics: measurements of the time-dependent C P asymmetry in B0 → K0Sπ0γ and the branching ratio of Bs → e±μ∓ decay possess, along with the anomalous magnetic moment of muon. In the mass range of sub-GeV, accessible by the flavorful ALPs search, the experimental sensitivity for these flavor observables reaches the maximum at around the pion mass scale (called the sweetest spots), where a couple of loopholes (unexplored regions) for the ALP parameter space have heretofore been present, because of an unavoidable contamination with pion background events. The proposed complementary probes can precisely determine the ALP coupling to photon at these sweetest spots/loopholes, and will significantly help cover whole parameter spaces in the ALP search including the present loopholes in the future.