New constraints on axion with gamma-ray observations of the Crab Nebula

TL;DR

This paper establishes new upper bounds on axion-like particle coupling using gamma-ray data from the Crab Nebula, emphasizing the importance of magnetic field modeling in such analyses.

Contribution

It introduces the first detailed consideration of the Crab Nebula's magnetic field effects in ALP-photon conversion constraints.

Findings

Constraints on ALP-photon coupling reach up to 1e-11 GeV^-1.

Magnetic field modeling significantly impacts conversion probability.

Proper magnetic field consideration is crucial for accurate ALP searches.

Abstract

In this paper, we derive the upper bounds on the coupling of axion-like particles (ALPs) with photon as a function of the mass by considering axion-photon conversion in the Crab Nebula. Previous studies have not considered the influence of the magnetic field within the Crab Nebula. The magnetic field plays a crucial role through the Synchrotron Self-Compton (SSC) process, in which high-energy electrons produce synchrotron radiation that is subsequently up-scattered by the same electrons via inverse Compton scattering to generate gamma rays. Therefore, neglecting the magnetic field in modeling leads to theoretical inconsistencies. In this work, we investigate the significance of the magnetic field effect and demonstrate that even differences in magnetic field modeling can substantially alter the conversion probability. We thus, for the first time, point out that proper consideration of the magnetic field is essential in ALP searches using gamma rays from the Crab Nebula. The resulting constraints reach up to a coupling of $g_{a\gamma \gamma} \lesssim 1 \times 10^{-11} {\rm GeV}^{-1}$ for ALP masses in the range $10^{-10} {\rm eV} \lesssim m_a \lesssim 10^{-6} {\rm eV}$.