Abstract
Using the helicity formalism, we calculate the combined angular distribution function of the two gamma photons and the electron in the cascade process \({\bar{p}p}\to{}^{3}{D}_{2}\to\chi_{J}+\gamma_{1}\to(\psi +\gamma_{2})+\gamma_{1}\to({e}^{+}+{e}^{-})+\gamma_{1}+\gamma_{2}\) (J=0,1,2), when \({\bar{p}}\) and p are arbitrarily polarized. We also present the partially integrated angular distribution functions in six different cases. Our results show that by measuring the two-particle angular distribution of γ 1 and γ 2 and that of γ 1 and e −, one can determine the relative magnitudes as well as the relative phases of all the helicity amplitudes in the two radiative decay processes 3 D 2→χ J +γ 1 and χ J →ψ+γ 2.
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Mok, A.W.K., Sebastian, K.J. Angular distributions in the decays of the triplet D 2 state of charmonium directly produced in polarized proton–antiproton collisions. Eur. Phys. J. C 63, 101–114 (2009). https://doi.org/10.1140/epjc/s10052-009-1091-2
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DOI: https://doi.org/10.1140/epjc/s10052-009-1091-2