A New Flavor of Searches for Axion-Like Particles

Abstract: We propose new searches for axion-like particles (ALPs) produced in flavor-changing neutral current (FCNC) processes. This proposal exploits the often-overlooked coupling of ALPs to W bosons, leading to FCNC production of ALPs even in the absence of a direct coupling to fermions. Our proposed searches for resonant ALP production in decays such as $B\rightarrow K^{(*)}a,\,a\rightarrow \gamma\gamma$ and $K\rightarrow \pi a, \,a\rightarrow \gamma\gamma$ could greatly improve upon the current sensitivity to ALP couplings to Standard Model particles. We also determine analogous constraints and discovery prospects for invisibly decaying ALPs.