A study of spin alignment of $\rho(770)^{\pm}$ and $\omega(782)$ mesons in hadronic Z $^0$ decays

Abstract

The helicity density matrix elements $\rho_{00}$ of $\rho(770)^{\pm}$ and $\omega(782)$ mesons produced in Z $^0$ decays have been measured using the OPAL detector at LEP. Over the measured meson energy range, the values are compatible with 1/3, corresponding to a statistical mix of helicity $-1$ , 0 and +1 states. For the highest accessible scaled energy range 0.3 $<$ $x_E$ $<$ 0.6, the measured $\rho_{00}$ values of the $\rho^{\pm}$ and the $\omega$ are 0.373 $\pm$ 0.052 and 0.142 $\pm$ 0.114, respectively. These results are compared to measurements of other vector mesons.