${{\boldsymbol \pi}^{+}}{{\boldsymbol \pi}^{-}}{{\boldsymbol \gamma}}$ PARAMETER $\beta $ (${\boldsymbol D}{\mathrm -wave}$)
INSPIRE search
Sensitive to a ${\mathit D}{\mathrm -wave}$ contribution: $\mathit dN/\mathit d$cos $\theta $ = sin$^2\theta $ ${}$ (1 + $\beta $ ${}$ cos $^2\theta $).