Speaker
Description
In this work, we present a comprehensive analysis of axion-meson mixing and scattering processes at leading order in three-flavor, large Nc chiral perturbation theory (ChPT). Treating the axion as a general axion-like particle (ALP) coupled derivatively to quark axial currents, we construct the effective chiral Lagrangian including meson and axion degrees of freedom, with all mixing effects consistently accounted for via a chiral rotation of the quark mass matrix.
We systematically derive the kinetic and mass mixing matrices for the neutral fields that, after the necessary rotations, give rise to the physical axion and the known neutral mesons (π⁰, η, η′). We perform this diagonalization at a leading order in the ratio of the pion and axion decay constants, F/fa, and include a full analysis of the leading order isospin breaking corrections to the axion-meson mixing angles.
Having calculated the physical states of the axion and mesons, we present the full leading order 4 field Lagrangian that allows us to calculate 1→3 decays and 2→2 scattering processes. We present general parameterizations of those amplitudes for an arbitrary number of axions in the initial and final states and provide simple methods to calculate the coefficients these amplitudes depend on.
Our method allows us to obtain a complete and comprehensive description of axion-meson interactions at a leading order, accounting for isospin breaking, and a direct relation between the parameters of the ultraviolet theory (axion-quark couplings) and those of the low-energy effective theory (axion-meson mixing angles). Also, we provide guidelines to easily extrapolate this analysis to NLO calculations or to focus on a particular axion model, that being an ALP or the QCD axion.
The very general character of our axion model opens the door for future uses on different fields, having the possibility to search for ALPs in the ~MeV mass range on particle colliders or lighter species as a dark matter candidate.
