Strong supernovae bounds on ALPs from quantum loops

Abstract: We show that in theories of axionlike particles (ALPs) coupled to electrons at tree-level, the one-loop effective coupling to photons is process dependent: the effective coupling relevant for decay processes, $g_{a\gamma}^{\text{(D)}}$, differs significantly from the coupling appearing in the phenomenologically important Primakoff process, $g_{a\gamma}^{\text{(P)}}$. We show that this has important implications for the physics of massive ALPs in hot and dense environments, such as supernovae. We derive, as a consequence, new limits on the ALP-electron coupling, $\hat{g}{ae}$, from SN 1987A by accounting for all relevant production processes, including one-loop processes, and considering bounds from excess cooling as well as the absence of an associated gamma-ray burst from ALP decays. Our limits are among the strongest to date for ALP masses in the range $0.03 \, \text{MeV} \, < m_a< 240 \, \text{MeV}$. Moreover, we also show how cosmological bounds on the ALP-photon coupling translate into new, strong limits on $\hat{g}{ae}$ at one loop. Our analysis emphasises that large hierarchies between ALP effective couplings are difficult to realise once quantum loops are taken into account.