Revisiting the Dark Photon Explanation of the Muon Anomalous Magnetic Moment

Understand

A massive $U(1)^{\prime}$ gauge boson known as a "dark photon" or $A^{\prime}$, has long been proposed as a potential explanation for the discrepancy observed between the experimental measurement and theoretical determination of the anomalous magnetic moment of the muon, ($g_{\mu} - 2$) anomaly.

• Recently, experimental results have excluded this possibility for a dark photon exhibiting exclusively visible or invisible decays.
• In this work, we revisit this idea and consider a model where $A^{\prime}$ couples inelastically to dark matter and an excited dark sector state, leading to a more exotic decay topology we refer to as a semi-visible decay.
• We show that for large mass splittings between the dark sector states this decay mode is enhanced, weakening the previous invisibly decaying dark photon bounds.