Speaker
Description
One of the strongest bounds on MeV-scale Axion-Like Particles (ALPs) interacting with photons is derived from the non-observation of a gamma-ray burst following Supernova (SN) 1987A. We strengthen this bound by including photon coalescence as an efficient production process of heavy ALPs. Furthermore, we present in some detail a new analytical method for calculating the predicted gamma-ray signal from ALP decays. With this method we can rigorously prove the validity of an approximation that has so far been used in some of the previous literature, which we show here to be valid only if all gamma rays arrive under extremely small observation angles (i.e. very close to the line of sight to the SN). However, it also shows where the approximation is not valid, and offers an efficient alternative to calculate the ALP-induced gamma-ray flux in a general setting when the observation angles are not guaranteed to be small. Finally, we show that it may be possible to reconstruct the product $ g_{a\gamma}^2 m_a $ from a potential future detection of this signal by the Fermi Large Area Telescope.
