Conserved Currents are Not Anomaly-Safe

TL;DR

This paper demonstrates that conserved currents coupled to new vector bosons can lead to enhanced rare decay processes due to anomalies, imposing strong constraints on models like $U(1)_{B-L}$ and $U(1)_{B_3 - L_2}$.

Contribution

It reveals the anomaly-induced enhancements in processes involving conserved currents and analyzes their implications for specific gauge extensions of the Standard Model.

Findings

Enhanced rates in rare Z and meson decays due to anomalies.

Constraints on $U(1)_{B-L}$ and $U(1)_{B_3 - L_2}$ models from decay processes.

Parameter space restrictions for models addressing the $(g-2)_rac{2}{ ext{mu}}$ anomaly.

Abstract

New vector bosons that are coupled to conserved currents in the Standard Model exhibit enhanced rates below the electroweak scale from anomalous triangle amplitudes, leading to (energy/vector mass)$^2$ enhancements to rare Z decays and flavor-changing meson decays into the longitudinally polarized vector boson. In the case of a vector boson gauging $U(1)_{B-L}$, the mass gap between the top quark and the remaining SM fermions leads to (energy/vector mass)$^2$ enhancements for processes with momentum transfer below the top mass. In addition, we examine the case of an intergenerational $U(1)_{B_3 - L_2}$ that has been proposed to resolve the $(g-2)_\mu$ anomaly with an MeV scale DM candidate, and we find that these enhanced processes constrain the entire parameter space.