The psion family: Relativistic charmonium

The authors have reported earlier that the spectrum of the psion family suggests a treatment based on an O(4) harmonic-oscillator family with O(4) quantum number $M=0$ (equally spaced, mass-squared linear Regge trajectories). This results in the new JPC quantum numbers: 0⁺⁺ for 2.8 GeV/c²; 2⁺⁺, 1^-+, 0⁺⁺ for the 3.4-GeV/c² mass region. All radiative decays are related through a single O(4) coupling S_μνF_μν, where S_μν is the internal-space angular-momentum operator. In this article the details of the calculations of radiative transition widths and of the γγ angular correlation functions are given. Experimental signatures are discussed and compared with the nonrelativistic charmonium scheme; among others J→O(2.8)+γ and ψ^'→O(2.8)+γ are small, being forbidden in the strict O(4) limit. $O(2.8)$ is expected to be narrow like all other psions below the 4.0-GeV/c² region. χ₀(3.41) and χ₁(3.49) total widths are expected to be around 630 keV and 185 keV, respectively. The missing decays of ψ^' could be due to ψ^'→O+ω(~32%).