New weakly coupled forces hidden in low-energy QCD

Is it possible to detect a new weakly coupled force at the QCD scale that interacts primarily with quarks? This work investigates experimental signatures of a new MeV--GeV gauge boson that couples to the baryon number, with attention to the 100 MeV--GeV mass range that is the regime of nonperturbative QCD. Such a state can be searched for in rare radiative decays of light mesons (η,η^',φ,ω) as a π⁰γ resonance, which is its leading decay mode from 140 to 620 MeV. This is a new discovery window for forces beyond the Standard Model that is not covered by existing dark photon searches.