Dark forces coupled to non-conserved currents

TL;DR

This paper establishes new, stronger constraints on light vector particles coupled to non-conserved currents, using rare decay processes, impacting various theoretical models involving such vectors.

Contribution

It derives novel bounds on light vectors with dimension-4 couplings to Standard Model particles, especially when coupled to non-conserved currents, surpassing previous limits.

Findings

New constraints from rare Z decays.

Stronger limits from flavor-changing meson decays.

Exclusion of several phenomenologically-motivated models.

Abstract

New light vectors with dimension-4 couplings to Standard Model states have (energy / vector mass)^2 enhanced production rates unless the current they couple to is conserved. These processes allow us to derive new constraints on the couplings of such vectors, that are significantly stronger than the previous literature for a wide variety of models. Examples include vectors with axial couplings to quarks and vectors coupled to currents (such as baryon number) that are only broken by the chiral anomaly. Our new limits arise from a range of processes, including rare Z decays and flavor changing meson decays, and rule out a number of phenomenologically-motivated proposals.