PASSAT: Particle Accelerator helioScopes for Slim Axion-like-particle deTection

TL;DR

PASSAT is a novel experimental approach that uses particle accelerators and magnetic fields to detect slim axion-like particles via photon conversion, expanding the accessible parameter space beyond previous lab and astrophysical methods.

Contribution

This paper introduces PASSAT, a new method for ALP detection at accelerators, reinterprets existing data, and proposes feasible low-cost experiments using existing magnets to explore previously inaccessible ALP parameter space.

Findings

Reinterpreted NOMAD data to constrain ALPs below 100 eV and coupling > 10^{-4} GeV^{-1}

Proposed using CAST and BabyIAXO magnets at CERN for improved sensitivity

Identified regions of ALP parameter space not yet probed by lab experiments

Abstract

We propose a novel method to search for axion-like particles (ALPs) at particle accelerator experiments (exps). ALPs produced at the target via the Primakoff effect subsequently enter a region with a magnetic field, where they are converted to photons that are then detected. Dubbed Particle Accelerator helioScopes for Slim Axion-like-particle deTection (PASSAT), our proposal uses the principle of the axion helioscope but replaces ALPs produced in Sun with those produced in a target material. Since we rely on ALP-photon conversions, our proposal probes light (slim) ALPs that are otherwise inaccessible to lab-based exps which rely on ALP decay, and complements astrophysical probes that are more model-dependent. We first reinterpret existing data from the NOMAD exp in light of PASSAT, and constrain the parameter space for ALPs lighter than ~100 eV and ALP-photon coupling larger than ~$10^{-4}$ GeV$^{-1}$. As benchmarks of feasible low-cost exps improving over the NOMAD limits, we study the possibility of reusing the magnets of the CAST and the proposed BabyIAXO exps and placing them at the proposed BDF facility at CERN, along with some new detectors. We find that these realizations of PASSAT allow for a direct probe of the parameter space for ALPs lighter than ~100 eV and ALP-photon coupling larger than ~4 x $10^{-6}$ GeV$^{-1}$, which are regions that have not been probed yet by exps with lab-produced ALPs. In contrast to other proposals aiming at detecting 1 or 2-photon only events in hadronic beam dump environments, that rely heavily on Monte Carlo simulations, the background (BG) in our proposal can be directly measured in-situ, its suppression optimized, and the irreducible BG statistically subtracted. Sensitivity studies with other beams will be the subject of future work. The measurements suggested here represent an additional physics case for the BDF beyond those already proposed.