Evidence for a new light spin-zero boson from cosmological gamma-ray propagation?

TL;DR

This paper proposes that gamma-ray transparency anomalies can be explained by photons oscillating into a new light spin-zero boson in intergalactic magnetic fields, offering a potential test for dark energy models.

Contribution

It introduces a mechanism where photons convert into a light boson, explaining gamma-ray transparency and linking it to dark energy models with observable predictions.

Findings

Gamma-ray transparency can be explained by photon-boson oscillations.

Predicted gamma-ray fluxes from blazar 3C279 match observations.

Testable predictions for gamma-ray telescopes are provided.

Abstract

Recent findings by Imaging Atmospheric Cherenkov Telescopes indicate a large transparency of the Universe to gamma rays, which can be hardly explained within the current models of extragalactic background light. We show that the observed transparency is naturally produced by an oscillation mechanism -- which can occur inside intergalactic magnetic fields -- whereby a photon can become a new spin-zero boson with mass m << 10^(-10) eV. Because the latter particle travels unimpeded throughout the Universe, photons can reach the observer even if the distance from the source considerably exceeds their mean free path. We compute the expected flux of gamma rays from blazar 3C279 at different energies. Our predictions can be tested in the near future by the gamma-ray telescopes H.E.S.S., MAGIC, CANGAROO and VERITAS. Moreover, our result provides an important observational test for models of dark energy wherein quintessence is coupled to the photon through an effective dimension-five operator.