${\chi }_{c2}\to \rho \rho$ and the $rho$ polarization in massless perturbative QCD: how to test the distribution amplitudes

Abstract

We compute the helicity density matrix of $\rho$ vector mesons produced in the two-body decays of polarized ${\chi }_{c2}$'s in the framework of massless perturbative QCD. The ${\chi }_{c2}$'s are either exclusively or inclusively produced in $p\bar{p}$ or $pp$ interactions, via quark-antiquark annihilation or gluon fusion. Our results show unambiguous significant differences depending on the choice of the $\rho$ distribution amplitudes and allow to discriminate between different proposed models.

Comments: 9 pages + 4 figures, REVTEX 3.0, figures appended as uuencoded, compressed postscript file