Measuring the phase between strong and EM J/psi decay amplitudes

QCD is certainly a well established theory describing strong interactions. Yet several physics topics which could be investigated with modern facilities can still offer various test of this theory. The investigation of the kinematic region near J/ψ production can provide a check of the QCD perturbative approach. In this energy range, an interference between the resonant e+ e− → J/ψ → hadrons and the non-resonant e+ e− → hadrons amplitudes can in principle occur. A perturbative approach suggests that those amplitudes are expected to be all almost real, i.e. the relative phase between the above cited amplitudes is expected to be 0◦/180◦, depicting hence the full interference scenario. Nevertheless, data available in the literature concordantly suggest a relative phase of 90◦ and, hence, the no interference scenario. An experimental approach able to provide a measurement of the relative phase in a model independent way, and in particular its deployment in the BESIII scenario, will be discussed in details.