Inelastic electromagnetic production of J/ψ in p–p ultra-peripheral collisions

J/ψ production in p–p ultra-peripheral collisions through the inelastic electromagnetic process, where the virtual photons emitted from the incoming nucleon interact with the partons in the target nucleon, is studied. The comparisons between the results of the equivalent photon approximation approach and the exact treatment ones are presented. Based on the method of Martin and Ryskin, the coherent and incoherent contributions are considered simultaneously. The distributions of Q2 (virtuality of the photon) and the total cross sections are calculated. The numerical results show that, the equivalent photon approximation approach is only effective in the Q2→∞ region where Qmax2 is small enough. It can be seen that an improper choice of Qmax2 will cause obvious errors in the equivalent photon approximation approach (the total cross sections are more than twice larger than the exact ones), and the exact treatment needs to be adopted to dealing with the widely kinematics region of Q2.