Abstract
New pseudo-scalars, often called axion-like particles (ALPs), abound in model-building and are often associated with the breaking of a new symmetry. Traditional searches and indirect bounds are limited to light axions, typically in or below the KeV range for ALPs coupled to photons. We present collider bounds on ALPs from mono-γ, tri-γ and mono-jet searches in a model independent fashion, as well as the prospects for the LHC and future machines. We find that they are complementary to existing searches, as they are sensitive to heavier ALPs and have the capability to cover an otherwise inaccessible region of parameter space. We also show that, assuming certain model dependent correlations between the ALP coupling to photons and gluons as well as considering the validity of the effective description of ALP interactions, mono-jet searches are in fact more suitable and effective in indirectly constraining ALP scenarios.
Highlights
A long time has passed since the work of Peccei and Quinn [1], and yet no concrete hint of axion-like particles (ALPs) has been found
We explore a wide range of the ALP parameter space, where interactions and masses violate the symmetry responsible for the ALPs origin
We aim to summarise current and prospective collider limits on the (Ma, gaX ) parameter space against the well known astrophysical and cosmological bounds to identify regions in which collider physics can be a complementary avenue to search for ALPs
Summary
A long time has passed since the work of Peccei and Quinn [1], and yet no concrete hint of ALPs has been found. In the original formulation, the Peccei-Quinn-Weinberg-Wilzcek (PQWW) axion, the scale of the interactions was related to the scale of electroweak symmetry breaking, and quite constrained. As this minimal realisation of a QCD axion was set aside, the idea of invisible axions, with interactions suppressed by much higher scales, arose. ALPs interactions are bounded from both sides: if they are too weak, ALPs could be stable and overclose the Universe, If they interact too strongly, they would affect processes such stellar formation These cosmological/astrophysics limits depend on how well one can identify axions as the sole player in the relevant processes.
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