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PreprintarXiv licencearXiv

Semi-analytical two-loop QCD corrections to e+e-→ J/ψ+χcJ at B factories

  • Hao-Yang Liu
  • Cong Li
  • Wen-Long Sang
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Abstract

In this work, we compute the next-to-next-to-leading-order (NNLO) QCD corrections to the process e+e-→ J/ψ+χcJ at B factories within the NRQCD factorization framework. The helicity amplitudes are obtained via asymptotic expansions around r=0 and r=1, with r=16mc2/s. Our asymptotic expressions reproduce the exact numerical results with high accuracy across the kinematic range 0≤ r ≤ 1, achieving a relative error below 10−5, which is sufficient for phenomenological applications. Notably, the large logarithmic terms are obtained analytically, and the explicit expressions established in this work provide a useful basis for further theoretical investigations. We compute the unpolarized cross sections. The 𝒪(αs) correction is found to be large, while the 𝒪(αs2) correction for χc0 production amounts to 33% of the leading-order (LO) cross section, significantly reducing the scale uncertainties. For χc1, the 𝒪(αs) and 𝒪(αs2) corrections correspond to 35% and −15%, respectively. For χc2, the corresponding corrections are 24% and −38%. The large cancellation between the corrections for χc2 brings the NNLO cross section close to the LO prediction. Our prediction for χc0 is consistent with both the {\tt Belle} and {\tt BaBar} data within uncertainties. We also predict the angular distribution parameters αJθ, which are independent of nonperturbative inputs. A sharp discrepancy between the theory and the {\tt Belle} measurement is observed for α0θ, calling for further experimental and theoretical investigations. Moreover, future measurements of the angular distribution parameters for χc1 and χc2 will provide important tests of the theoretical framework.

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Cite

BibTeXRIS
BibTeX
@misc{liu2026semianalytical,
  title = {{Semi-analytical two-loop QCD corrections to $e^+e^-\to J/ψ+χ_cJ$ at B factories}},
  author = {Hao-Yang Liu and Cong Li and Wen-Long Sang},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2606.02182},
  eprint = {2606.02182},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2606.02182},
}
RIS
TY  - UNPB
TI  - Semi-analytical two-loop QCD corrections to e^+e^-→ J/ψ+χ_cJ at B factories
AU  - Hao-Yang Liu
AU  - Cong Li
AU  - Wen-Long Sang
PY  - 2026
DA  - 2026/09/24
PB  - arXiv
DO  - 10.48550/arxiv.2606.02182
UR  - https://arxiv.org/abs/2606.02182
AB  - In this work, we compute the next-to-next-to-leading-order (NNLO) QCD corrections to the process e^+e^-→ J/ψ+χ_cJ at B factories within the NRQCD factorization framework. The helicity amplitudes are obtained via asymptotic expansions around r=0 and r=1, with r=16m_c^2/s. Our asymptotic expressions reproduce the exact numerical results with high accuracy across the kinematic range 0≤ r ≤ 1, achieving a relative error below 10^−5, which is sufficient for phenomenological applications. Notably, the large logarithmic terms are obtained analytically, and the explicit expressions established in this work provide a useful basis for further theoretical investigations. We compute the unpolarized cross sections. The 𝒪(α_s) correction is found to be large, while the 𝒪(α_s^2) correction for χ_c0 production amounts to 33% of the leading-order (LO) cross section, significantly reducing the scale uncertainties. For χ_c1, the 𝒪(α_s) and 𝒪(α_s^2) corrections correspond to 35% and −15%, respectively. For χ_c2, the corresponding corrections are 24% and −38%. The large cancellation between the corrections for χ_c2 brings the NNLO cross section close to the LO prediction. Our prediction for χ_c0 is consistent with both the {\tt Belle} and {\tt BaBar} data within uncertainties. We also predict the angular distribution parameters α^J_θ, which are independent of nonperturbative inputs. A sharp discrepancy between the theory and the {\tt Belle} measurement is observed for α^0_θ, calling for further experimental and theoretical investigations. Moreover, future measurements of the angular distribution parameters for χ_c1 and χ_c2 will provide important tests of the theoretical framework.
ER  -