# New constraints on light vectors coupled to anomalous currents

## TL;DR

This paper establishes new experimental constraints on light vectors coupled to SM fermions, especially when anomalies are canceled by heavy fermions, leading to enhanced decay rates and stronger bounds on their couplings.

## Contribution

It derives novel constraints on anomalous light vectors, incorporating Wess-Zumino interactions and anomaly cancellation effects, extending previous bounds significantly.

## Key findings

- Enhanced decay rates for Z and meson decays involving the new vector.
- Stronger coupling bounds over a wide mass range.
- Implications for models with anomalous gauge interactions.

## 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. 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 baryon number, Z decays and flavour 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.