Off-diagonal helicity density matrix elements for vector mesons produced in polarized $e^+e^-$ processes

Abstract

Final-state $q \bar q$ interactions give origin to nonzero values of the off-diagonal element $\rho_{1,-1}$ of the helicity density matrix of vector mesons produced in $e^+ e^-$ annihilations, as has been confirmed by recent OPAL data on $\phi$ , $D^*$ , and $K^*$ . New predictions are given for $\rho_{1,-1}$ of several mesons produced at large $x_{_\mathrm{E}}$ and small $p_\mathrm{T}$ – i.e., collinear with the parent jet – in the annihilation of polarized $e^+$ and $e^-$ ; the results depend strongly on the elementary dynamics and allow further nontrivial tests of the standard model.