Soft photon spectrum in orthopositronium and vector quarkonium decays

QED gauge invariance, when combined with analyticity, leads to constraints on the low energy end of the emitted photon spectra. This is known as Lowʹs theorem. It is shown that the Ore–Powell result, as well as further developments for the orthopositronium differential decay rate, are in contradiction with Lowʹs theorem, i.e., that their predicted soft photon spectra are incorrect. A solution to this problem is presented. The implications for the orthopositronium lifetime puzzle, the charmonium ρ–π puzzle, the prompt photon spectrum in inclusive quarkonium decays and the extraction of αS from quarkonium annihilation rates are briefly commented.