$χ_{c2} \to ρρ$ Decay and the $ρ$ Polarization in Inclusive Processes: A Test of Mass Effects

Abstract

We compute the helicity density matrix of $ρ$ vector mesons produced in the two-body decays of $χ_{c2}$'s in the framework of perturbative QCD, allowing for mass corrections. The $χ_{c2}$'s are inclusively produced in hadronic interactions via gluon fusion and are shown to be strongly polarized. Both the case in which the light quarks inside the final mesons are treated as massless current quarks and the case in which they are seen as constituent massive ones are considered. Our results show significant differences between the two cases; the measurement of the $ρ$ helicity density matrix should allow a test of the importance of these mass effects.