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 ${\chi }_{c1\mathrm{}}$ and ${\chi }_{c2\mathrm{}}$ 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 ${\chi }_{c1\mathrm{}}$ and 5908 ${\chi }_{c2\mathrm{}}$ events, we have measured the fractional magnetic quadrupole amplitude to be $a_2\left({\chi }_{c1\mathrm{}}\right)\simeq M2/E1=0.002\mathrm{}\pm 0.032,$ and $a_2\left({\chi }_{c2\mathrm{}}\right)=-{0.093}_{-0.041}^{+0.039\mathrm{}}.$ We have also measured the square of the helicity 0 fractional amplitude in the ${\chi }_{c2\mathrm{}}$ formation process to be $B_0^2=0.13\mathrm{}\pm \mathrm{0.08.}$