New Constraints on Light Vectors Coupled to Anomalous Currents

Abstract

We derive new constraints on light vectors coupled to standard model (SM) fermions, when the corresponding SM current is broken by the chiral anomaly. The cancellation of the anomaly by heavy fermions results, in the low-energy theory, in Wess-Zumino-type interactions between the new vector and the SM gauge bosons. These interactions are determined by the requirement that the heavy sector preserves the SM gauge groups and lead to (energy/vector mass)^{2} enhanced rates for processes involving the longitudinal mode of the new vector. Taking the example of a vector coupled to a vector coupled to SM baryon number, Z decays and flavor-changing neutral current meson decays via the new vector can occur with (weak scale/vector mass)^{2} enhanced rates. These processes place significantly stronger coupling bounds than others considered in the literature, over a wide range of vector masses.

Light resonances and the low-q2 bin of $$ {R}_{K^{*}} $$

“…One can also wonder how a direct coupling of the vector to the bs current in Q (4) and Q (4) is possible. Recent studies have shown that these interactions do indeed arise in models where a light V couples to quark currents that are not conserved when the SM mass terms and/or quantum anomaly effects are taken into account [35,36]. Models with direct flavour-universal couplings of V to the axial-vector current of quarks tend to develop Q (4) at one loop, while models with a coupling of V to any linear combination of lepton and baryon currents other than B − L induce Q (4) at the two-loop level.…”

“…For Q (4) we assume that the interaction is induced by the couplings of the vector to anomalous currents in which case the coupling is two-loop suppressed [35] and we have…”

“…is a loop function of order one defined in [35]. In other classes of models, this coupling can be induced at one-loop [36], or at tree-level [37,38].…”

“…[35] is gauged baryon number with a gauge coupling g X and with a small kinetic mixing of the U(1) B and the photon. The translation from our coupling C 4 to this model is…”

Exposing the dark sector with future Z factories

“…The fourth topology, denoted as 1D, is Z → A 0 γ → ðχχÞγ. It can come from the Wess-Zumino term ϵ μνρσ A 0 μ B ν ∂ ρ B σ when the dark photons couple to anomalous currents [130,131,131]. After integrating by parts, the longitudinal part of A 0 has interaction similar to the topology 1C; thus, the limit on the exotic Zdecay BR is similar to 1C.…”