Polarized angular distributions in the decays of the singlet D ₂ state of charmonium originating from $\bar{p}p$ collisions

Abstract

Using the helicity formalism, we calculate the combined angular distribution function of the neutral pion (π ⁰) and the polarized electron (e ⁻) and photon (γ) produced in the triple cascade process $\bar{p}+p\rightarrow{}^{1}D_{2}\rightarrow{}^{1}P_{1}+\gamma\rightarrow(\psi +\pi^{0})+\gamma \rightarrow(e^{-}+e^{+})+\pi^{0}+\gamma$, when $\bar{p}$ and p are unpolarized. We also present the partially integrated angular distribution functions in three different cases where the combined angular distribution function of the three particles is integrated over the direction of one of the particles. Our results show that by measuring the two-particle angular distribution of the electron and the photon with the polarization of either particle, one can determine the relative magnitudes as well as the relative phases of all the angular-momentum helicity amplitudes in the two decay processes ¹ D ₂→¹ P ₁+γ and ¹ P ₁→ψ+π ⁰.