ALP Searches at the LHC: FASER as a Light Shining through Walls Experiment

TL;DR

This paper proposes using the FASER experiment at the LHC as a novel light-shining-through-walls setup to detect axions and ALPs by exploiting high-energy photon flux and magnetic field conversions, expanding the search parameter space.

Contribution

It introduces a new experimental approach utilizing FASER as a light-shining-through-walls setup for ALP detection at the LHC, which can probe previously inaccessible parameter regions.

Findings

FASER can detect ALPs via photon-ALP-photon conversions.

FASER and FASER2 will explore new ALP parameter space.

Potential to improve constraints on ALP properties.

Abstract

We propose the use of FASER as a light-shining-through-walls experiment to search for axions and axion-like particles (ALPs). LHC collisions generate a high intensity and high energy photon flux in the forward direction which can oscillate into ALPs in the magnetic fields that are used to confine the beam. These ALPs then pass through about 100~m of rock before reaching the magnetic fields of FASER, where they can convert back into photons and be detected by an electromagnetic calorimeter. In the next years, FASER and its successor FASER2 at the Forward Physics Facility will be able to explore regions of the ALPs parameter space inaccessible by other laboratory-based experiments.