Coupling charmonium to the charmed-meson sector

The cc¯ states of charmonium are coupled by means of the pair production of light quarks to charmed-meson states. The coupling operator is derived from a reduction of the Feynman amplitude for pair production. The potential and wave functions used are those of the Stanley-Robson model. Energy shifts for the first three $J^P$ ${=1\mathrm{}}^{\mathrm{-}}$ states are found to be in the range 50–80 MeV downward. The calculated width of the state ψ’ ’(3770) is 14 MeV, which compares favorably with the observed value. Extension of these calculations to lighter and heavier meson systems is briefly considered in the concluding section. Suggestions for improvements and possible areas for further study are also given.