Next-to-leading-order study of J/ψ angular distributions in e+e-→ J/ψ + ηc, χcJ at √s ≈ 10.6 GeV

In this paper, we present a detailed next-to-leading-order (NLO) study of J/psi angular distributions in e(+)e(-) -> J/psi + eta(c), chi(cJ) (J = 0, 1, 2) within the nonrelativistic QCD factorization (NRQCD). The numerical NLO expressions for total and differential cross sections, i.e., d sigma/dcos theta - A + B cos(2)theta, are both derived. With the inclusion of the newly-calculated QCD corrections to A and B, the alpha(theta) (= B/A) parameters in J/psi + chi(c0) and J/psi + chi(c1) are moderately enhanced, while the magnitude of alpha(theta J/psi+chi c2) is significantly reduced; regarding the production of J/psi + eta(c), the alpha(theta) value remains unchanged. By comparing with experiment, we find the predicted alpha(theta J/psi+eta c) is in good agreement with the Belle measurement; however, alpha(theta J/psi+chi c0) is still totally incompatible with the experimental result, and this discrepancy seems to hardly be cured by proper choices of the charm-quark mass, the renormalization scale, and the NRQCD matrix elements.

Automated summary

This paper presents a detailed NLO study of J/psi angular distributions in e(+) e(-) -> J/psi + eta(c), chi(cJ) (J = 0, 1, 2) within NRQCD, deriving numerical expressions for total and differential cross sections. By comparing with experiment, it is found that the predicted result for J/psi + eta(c) is in good agreement with Belle measurement, while the result for J/psi + chi(c0) is totally incompatible with experimental data.