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 $B\rightarrow K^{(*)}a,\,a\rightarrow γγ$ and $K\rightarrow πa, \,a\rightarrow γγ$ 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.

7 pages, 4 figures. Appendix A added to show sensitivity to scenario with additional hypercharge couplings; references added; additional bound on K decays from E949 added (results qualitatively unchanged). Version to be published in PRL