Recently, the LHC collaborations, ATLAS and CMS, have announced an excess in the diphoton channel with local significance of about 3σ around an invariant mass distribution of ∼750 GeV, after analyzing new data collected at centre-of-mass energies of s=13TeV. We present a possible physical interpretation of such a signature, within the framework of a minimal UV-complete model with a massive singlet pseudo-scalar state a that couples to a new TeV-scale coloured vector-like fermion F, whose hypercharge quantum number is a non-zero integer. The pseudo-scalar state a might be a heavy pseudo-Goldstone boson, such as a heavy axion, which decays into two photons and whose mass lies around the excess region. The mass of the CP-odd state a and its coupling to F may be due to non-perturbative effects, which can break the original Goldstone shift symmetry dynamically. The possible role that the heavy axion a can play in the radiative generation of a seesaw Majorana scale and in the solution to the so-called strong CP problem is briefly discussed.
@article{arxiv.1512.04931,
title = {Diphoton Signatures from Heavy Axion Decays at the CERN Large Hadron Collider},
author = {Apostolos Pilaftsis},
journal= {arXiv preprint arXiv:1512.04931},
year = {2016}
}