Probing axion-like particles with $\gamma \gamma$ final states from vector boson fusion processes at the LHC

Abstract

We perform a feasibility study to search for axion-like particles (ALPs) using vector boson fusion (VBF) processes at the LHC. We work in an effective field theory framework with cutoff scale $\Lambda$ and ALP mass $m_{a}$, and assume that ALPs couple to photons with strength $\propto 1/\Lambda$. Assuming proton-proton collisions at $\sqrt{s} = 13$ TeV, we present the total VBF ALP production cross sections, ALP decay widths and lifetimes, and relevant kinematic distributions as a function of $m_{a}$ and $\Lambda$. We consider the $a\to\gamma\gamma$ decay mode to show that the requirement of an energetic diphoton pair combined with two forward jets with large dijet mass and pseudorapidity separation can significantly reduce the Standard Model backgrounds, leading to a $5\sigma$ discovery reach for $10 \text{ MeV} \lesssim m_{a} \lesssim 1$ TeV with $\Lambda \lesssim 2$ TeV, assuming an integrated luminosity of 3000 fb$^{-1}$. In particular, this extends the LHC sensitivity to a previously unstudied region of the ALP parameter space.