Constraints on Axion-Lepton coupling from Big Bang Nucleosynthesis

Abstract

In this article, we study the implications of the coupling between Axion-Like-Particles (ALPs) and Leptons to cosmology in particular, the Big Bang Nucleosynthesis (BBN) . We show that the BBN, through the constraint on the effective number of relativistic neutrino species, provides the most stringent bound on the ALP-electron interaction strength for the mass of axion between 20 keV and 1 MeV . For other values of the mass, the BBN bound complements the stellar-evolution and laboratory bounds.