# Exploring pseudo-Nambu--Goldstone bosons by stimulated photon colliders in the mass range 0.1~eV to 10~keV

## TL;DR

This paper proposes a method to search for pseudo-Nambu--Goldstone bosons in the 0.1 eV to 10 keV mass range using stimulated photon colliders, potentially testing string-theory-based particles beyond GUT scales.

## Contribution

It introduces a novel experimental approach using photon-photon scattering with laser pulses to detect pNGBs in an unexplored mass and coupling domain, incorporating quantum electrodynamic effects.

## Key findings

- Accessible large unexplored mass--coupling domain.
- Applicable formulae for photon--photon scattering via pNGB resonance.
- Potential to test string-theory-based pNGBs beyond GUT scale.

## Abstract

Searching for pseudo-Nambu--Goldstone bosons (pNGBs) in weak-coupling domains is crucial for understanding the dark components in the universe. We propose searching for pNGBs coupled to two photons in the mass range from 0.1~eV to 10~keV. This could provide opportunities to test string-theory-based pNGBs beyond the GUT scale $M \sim 10^{16}$~GeV included in the weak coupling proportional to $M^{-1}$. We provide formulae that are applicable to photon--photon scattering via a pNGB resonance exchange with a stimulation process in an asymmetric head-on photon--photon collider by mixing three laser pulses in laboratory experiments. We discuss the quantum electrodynamic effects on the pNGB exchange in the same mass--coupling domain as a background process from the standard model. We find that a large unexplored mass--coupling domain is accessible by combining existing laser facilities, including free-electron lasers.