Axial vectors in DarkCast

Abstract

In this work, we explore new spin-1 states with axial couplings to the standard model fermions. We develop a data-driven method to estimate their hadronic decay rates based on data from τ decays and using SU(3) flavor symmetry. We derive the current and future experimental constraints for several benchmark models. Our framework is generic and can be used for models with arbitrary vectorial and axial couplings to quarks. We have made our calculations publicly available by incorporating them into the DarkCast package, see https://gitlab.com/darkcast/releases.

On (g − 2)μ from gauged U(1)X

“…For processes where the mass can be neglected, such as NA64, there is no difference between the axial and the vectorial couplings. Also for the BaBar search, the above vector model reinterpretation still approximates rather well the actual bounds [130,131]. Below the di-muon threshold, the dominate decay channel of X is to invisible final states, while above the di-muon threshold there is a sizeable branching ratio for X → µ + µ − .…”