Probing MeV to 90 GeV axion-like particles with LEP and LHC

Axion-like particles (ALPs), relatively light (pseudo-)scalars coupled to two gauge bosons, are a common feature of many extensions of the Standard Model. Up to now there has been a gap in the sensitivity to such particles in the MeV to 10 GeV range. In this note we show that LEP data on Z -> gamma gamma decays provides significant constraints in this range (and indeed up to the Z-mass). We also discuss the sensitivities of LHC and future colliders. Particularly the LHC shows promising sensitivity in searching for a pseudo-scalar with 4 less than or similar to m(a) less than or similar to 60 GeV in the channel pp -> 3 gamma with m(3 gamma) approximate to m(Z). (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).