Vector meson dominance

The dominant lowest order coupling is to one virtual photon, so the simplest assumption is that J/ J is a = 1 state reached through one virtual photon exchange via mechanisms familiar from the theory of vector meson dominance used in discussing the u , 0 mesons. Fig. 11.9 shows various possibilities for the process e+e —> / in the region of the J/ mass. 

Renard, F. M. q-w Mixing (VoL 63) Schildknecht,D. Vector Meson Dominance, Photo-and Electroproduction from Nucleons (Vol. 63)... 

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