Search for an axion-like particle with forward proton scattering in association with photon pairs at ATLAS

A search for forward proton scattering in association with light-by-light mediated by an axion-like particle is presented, using the ATLAS Forward Proton spectrometer to detect scattered protons and central detector pairs of outgoing photons. Proton-proton collision data recorded 2017 at a centre-of-mass energy $\sqrt{s} = 13$ TeV were analysed, corresponding integrated luminosity 14.6 fb$^{-1}$. total 441 candidate signal events selected. was made narrow resonance diphoton mass distribution, (ALP) range 150-1600 GeV. No excess observed above smooth background. Upper limits on production cross section are set as function mass, interpreted upper ALP coupling constant, assuming 100% decay branching ratio into photon pair. The inferred limit constant 0.04-0.09 TeV$^{-1}$ 95%confidence level.