Axion-Like Particles at Future Colliders

TL;DR

This paper evaluates the potential of future colliders to discover axion-like particles (ALPs) across a range of masses and decay modes, emphasizing search strategies and the expected reach of various proposed experiments.

Contribution

It provides a comprehensive analysis of the discovery prospects for ALPs at future high-energy colliders, including detailed search strategies and sensitivity projections.

Findings

Future colliders can probe ALPs with masses below and above GeV scale.

Resonant production and decay channels are promising for ALP detection.

Electroweak precision measurements can constrain ALP couplings.

Abstract

Axion-like particles (ALPs) are pseudo Nambu-Goldstone bosons of spontaneously broken global symmetries in high-energy extensions of the Standard Model (SM). This makes them a prime target for future experiments aiming to discover new physics which addresses some of the open questions of the SM. While future high-precision experiments can discover ALPs with masses well below the GeV scale, heavier ALPs can be searched for at future high-energy lepton and hadron colliders. We discuss the reach of the different proposed colliders, focusing on resonant ALP production, ALP production in the decay of heavy SM resonances, and associate ALP production with photons, Z bosons or Higgs bosons. We consider the leading effective operators mediating interactions between the ALP and SM particles and discuss search strategies for ALPs decaying promptly as well as ALPs with delayed decays. Projections for the high-luminosity run of the LHC and its high-energy upgrade, CLIC, the future $e^+e^-$ ring-colliders CEPC and FCC-ee, the future pp colliders SPPC and FCC-hh, and for the MATHUSLA surface array are presented. We further discuss the constraining power of future measurements of electroweak precision parameters on the relevant ALP couplings.