Single- and Double-Pion Production in Nucleon Collisions on the Nucleon and on Nuclei -- the ABC Effect and its Possible Origin in a Dibaryonic Resonance

H. Clement, M. Bashkanov, E. Doroshkevich +5

The ABC effect -- an intriguing low-mass enhancement in the $\pi \pi$ invariant mass spectrum -- is known from inclusive measurements of two-pion production in nuclear fusion reactions.…