Study of the angular distribution of the reactionp¯p→χc2→Jψγ→e+e−γ

We report on a study of the angular distribution in the reaction $\overline{p}p\to {\chi }_{c2\mathrm{}}\to \frac{J}{\psi }\gamma \to e^{+}{e}^{-}\gamma$. Using a sample of 1904 events, we find that the contribution of helicity zero in the formation process is $B_0^2<0.22\mathrm{}$ (90% C.L.), and that the normalized quadrupole amplitude in the radiative decay is $a_2=-0.14\mathrm{}\pm 0.06$. The normalized radiative decay octupole amplitude $a_3$ is found to be consistent with zero.