The experimental challenge of detecting solar axion-like particles to test cosmological ALP-photon oscillation hypothesis

Abstract: We consider possible experimental tests of recent hypotheses suggesting that TeV photons survive the pair production interaction with extragalactic background light over cosmological distances by converting to axion-like particles (ALPs) in galactic magnetic fields. We show that proposed giant ultra-low background scintillation detectors will even have a difficult time reaching the present CAST sensitivity, which is one to two orders of magnitude less sensitive than necessary for a meaningful test of the ALP-photon oscillation hypothesis. Potential alternative tests are briefly discussed.