Next-to-leading-order QCD study of e⁺e⁻ → ηc + cc̄ at B factories

We study the process e⁺e⁻ → γ^ → ηc + cc̄ + X at next-to-leading order (NLO) in QCD within the framework of nonrelativistic QCD (NRQCD) factorization, retaining the color-singlet contribution at leading order in the heavy-quark relative velocity v. At the e⁺e⁻ collision energy √s = 10.6~GeV, with mc = 1.5~GeV and μR = 2mc, the direct cross section increases from 58.7~fb at leading order (LO) to 118~fb at NLO, corresponding to a K factor of approximately $2.0$. Including the radiative feed-down contributions of the $J/ψ$ and hc(1P) states yields an estimated prompt production rate of 131~fb. The NLO corrections substantially enhance both the angular and momentum distributions, while the momentum spectrum retains a similar overall profile. These results establish an NLO color-singlet baseline for ηc production associated with open charm at Belle II, complementary to studies of charmonium production in hadronic collisions.