Eur. Phys. J. C (2009) 63: 101-114
https://doi.org/10.1140/epjc/s10052-009-1091-2

Regular Article - Theoretical Physics

Angular distributions in the decays of the triplet D ₂ state of charmonium directly produced in polarized proton–antiproton collisions

¹ Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong
² Department of Physics, University of Massachusetts at Lowell, Lowell, MA, 01854, USA

^* e-mail: wkmok@hkbu.edu.hk

Received: 23 August 2008
Published online: 9 July 2009

Abstract

Using the helicity formalism, we calculate the combined angular distribution function of the two gamma photons and the electron in the cascade process (J=0,1,2), when 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.