Polarized J/ψ production at CLEO

Polarizations of the prompt -J/ψ's produced in the e ⁺e ^- annihilation at CLEO energy (√s = 10.58 GeV) are considered in the framework of the nonrelativistic quantum chromodynamics (NRQCD) factorization formalism. We find that the J/ψ polarization has a strong dependence on the production mechanism. At CLEO energy, the most dominant J/ψ production mechanism throughout most of phase space is the color-singlet mechanism, e ⁺e ^- → J/ψ + gg, for which J/ψ's are highly longitudinally polarized. On the other hand, the dominant J/ψ production mechanism at the upper endpoint of the J/ψ energy distribution is the color-octet process, e ⁺e ^- → (cc̄) ⁽⁸⁾ + g, for which J/ψ's are almost unpolarized. Thus, the measurement of the polarization of the endpoint J/ψ's is another test of the color-octet mechanism and a constraint on the NRQCD matrix elements.