Angular distributions in the reactions pp→χ1,2→γψ→γe+e−

Abstract In the experiment R704 at the CERN Intersecting Storage Rings, the two p-wave charmonium states χ 1 and χ 2 were formed directly in proton-antiproton annihilation, and detected through the decay chain χ j →γ+J ψ→ψ+ e + e − . The angular d istributions of the events found are studied here. A maximum likehood analysis shows that χ 1 radiative transition to the J ψ is compatible with a pure dipole. Indications of a nonzero, positive quadropole contribution to the χ 2 radiative transition are found. Finally, it is found that the χ 2 data are consistent with the conventional assumption that a single quark radiates the photon in the transition from the χ 2 to the J ψ .