as known the photon can have an isospin of 0 and 1. However, what is the ratio of both for an virtual photon (in e+e- annihilations)?
Next to an 1^-- resonance like J/Psi or Psi' it should be 1 in my opinion (as the resonance cross section is much higher than the continuum cross section).
But what ratio should one expect for the continuum? (I plan to estimate the ratio of Delta and Nucleon resonances within the continuum...)
Thanks for your help.