One-loop corrections to ALP couplings

TL;DR

This paper calculates one-loop corrections to axion-like particle (ALP) couplings to Standard Model particles, providing finite, gauge-invariant results crucial for interpreting experimental searches at colliders, astrophysical observations, and dark matter experiments.

Contribution

It presents the complete one-loop effective couplings of ALPs to SM particles, including finite corrections, in a gauge-invariant manner, and explores phenomenological implications for collider and astrophysical searches.

Findings

Derived one-loop ALP-SM effective couplings including finite corrections.

Analyzed phenomenological constraints on ALP-top quark coupling from LHC and dark matter experiments.

Clarified the role of gauge anomalies and basis choices in ALP interactions.

Abstract

The plethora of increasingly precise experiments which hunt for axion-like particles (ALPs), as well as their widely different energy reach, call for the theoretical understanding of ALP couplings at loop-level. We derive the one-loop contributions to ALP-SM effective couplings, including finite corrections. The complete leading-order -- dimension five -- effective linear Lagrangian is considered. The ALP is left off-shell, which is of particular impact on LHC and accelerator searches of ALP couplings to $\gamma\gamma$, $ZZ$, $Z\gamma$, $WW$, gluons and fermions. All results are obtained in the covariant $R_\xi$ gauge. A few phenomenological consequences are also explored as illustration, with flavour diagonal channels in the case of fermions: in particular, we explore constraints on the coupling of the ALP to top quarks, that can be extracted from LHC data, from astrophysical sources and from Dark Matter direct detection experiments such as PandaX, LUX and XENON1T. Furthermore, we clarify the relation between alternative ALP bases, the role of gauge anomalous couplings and their interface with chirality-conserving and chirality-flip fermion interactions, and we briefly discuss renormalization group aspects.