production in the di-muon channel

For the elastic process , the di-muon mass distribution is shown in Fig.4. The applied cuts are and (transverse momentum) >5GeV/c for both muons. The effect of can be clearly seen as a resonance peak around its mass. But unfortunately, the current HERA integrated luminosity is yet too small to observe the effect. The production cross-section seen in Fig.4 is about 0.002pb which is consistent with that of EPVEC.