A framework for missing-energy searches with anomalous light vectors

TL;DR

This paper develops a comprehensive framework for searching for light anomalous vectors that decay invisibly, integrating theoretical anomaly considerations with experimental constraints from flavor and electroweak processes.

Contribution

It classifies minimal anomalon spectra, derives effective interactions, and connects anomaly cancellation with experimental missing-energy searches.

Findings

Bound the UV completion scale using anomaly and naturalness considerations.

Surveyed current and future searches for invisible decays in flavor and electroweak processes.

Provided a unified phenomenological framework for anomalous light vectors with invisible decays.

Abstract

We study light spin-1 gauge bosons coupled to electroweak-anomalous currents. For generic charge assignments, anomaly cancellation requires new fermions (anomalons) that are chiral under the new abelian symmetry and carry electroweak charges. If their masses arise from the breaking of the new gauge symmetry, integrating them out generates Wess-Zumino interactions fixed by mixed-anomaly matching, providing the infrared description of the theory. We classify minimal anomalon spectra, derive the corresponding effective interactions, and combine experimental constraints with finite-naturalness considerations to bound the UV completion scale. Motivated by recent NA62 and Belle II results, we then develop a unified phenomenological framework for the missing-energy signatures of these anomalous light vectors, focusing on scenarios where the new vector decays predominantly into neutrinos so that the leading probes are rare processes with invisible final states. As applications, we survey current and projected searches across flavour and electroweak observables, including $K\to\pi E_{\rm miss}$, $B\to K^{(*)}E_{\rm miss}$, and $Z\to\gamma E_{\rm miss}$, and discuss their interplay with direct searches for anomalons.