χc2→ρρ and the ρ polarization in massless perturbative QCD: How to test the distribution amplitudes

We compute the helicity density matrix of ρ vector mesons produced in the two-body decays of polarized ${\mathrm{\chi }}_{\mathit{c}2}$’s in the framework of massless perturbative QCD. The ${\mathrm{\chi }}_{\mathit{c}2}$’s are either exclusively or inclusively produced in pp¯ or pp interactions, via quark-antiquark annihilation or gluon fusion. Our results show unambiguous significant differences depending on the choice of the ρ distribution amplitudes and allow us to discriminate between different proposed models. © 1996 The American Physical Society.