Speaker
Description
We explore the viability of axion-like particle (ALP) effective field theories (EFTs) where the ALP mass $m_a$ is comparable to or larger than the symmetry-breaking scale $f_a$, challenging the conventional hierarchy $m_a < f_a$. Using a data-driven approach, we analise four key observables: the anomalous magnetic moments of the electron and muon, as well as decays ($\mu\to e\gamma$) and ($\mu\to 3e$), considering an ALP coupled only to the less massive charged leptons with both flavour conserving and violating possibilities. Focusing on high ALP masses ($m_a>1$ GeV), we find a viable parameter space where $m_a\geq f_a$ remains consistent with experimental data within 3$\sigma$. This study highlights the potential for non-traditional ALP mass hierarchies in EFT scenarios.
