Experimental study of the relative phase between J/psi production amplitudes

QCD is undoubtably a well established theory that is able to describe strong interactions. Yet several open issues could be investigated by means of modern existing and forthcoming facilities, that would provide more tests of this theoretical framework. In particular a more detailed investigation in the kinematic region in the vicinity of J/ψ production can probe the validity 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. In a perturbative approach those amplitudes are expected to be all almost real, i.e. the relative phase between the above cited amplitudes is expected to be compatible with either 0° or 180°, implying a maximal interference scenario. Nevertheless, data available in the literature appear to suggest a no interference scenario implying a relative phase of ∼ 90°. An experimental approach able to provide a measurement of the relative phase in a model independent way, and in particular its deployment and its latest results in the BESIII scenario, will be discussed in details.