Study of the angular distributions of the reactionsp¯p→χc1,χc2→J/ψγ→e+e−γ

We report on a study of the angular distributions in the radiative decay of the ${\ensuremath{\chi}}_{c1}$ and ${\ensuremath{\chi}}_{c2}$ states formed in $\overline{p}p$ annihilations. These distributions depend on the dynamics of the formation process and the multipole structure of the radiative decay. Using 2090 ${\ensuremath{\chi}}_{c1}$ and 5908 ${\ensuremath{\chi}}_{c2}$ events, we have measured the fractional magnetic quadrupole amplitude to be ${a}_{2}({\ensuremath{\chi}}_{c1})\ensuremath{\simeq}M2/E1=0.002\ifmmode\pm\else\textpm\fi{}0.032,$ and ${a}_{2}({\ensuremath{\chi}}_{c2})=\ensuremath{-}{0.093}_{\ensuremath{-}0.041}^{+0.039}.$ We have also measured the square of the helicity 0 fractional amplitude in the ${\ensuremath{\chi}}_{c2}$ formation process to be ${B}_{0}^{2}=0.13\ifmmode\pm\else\textpm\fi{}0.08.$