The next-to-next-to-leading-order QCD corrections to $e^+e^-\to η_c/χ_{cJ}+γ$ at B factories
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| Format: | Preprint |
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2025
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| _version_ | 1866912749119864832 |
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| author | Li, Cong Sang, Wen-Long Zhang, Hong-Fei |
| author_facet | Li, Cong Sang, Wen-Long Zhang, Hong-Fei |
| contents | We investigate the processes $e^+e^-\to η_c+γ$ and $e^+e^-\to χ_{cJ}+γ$ at B factories within the NRQCD factorization framework, computing the corresponding helicity amplitudes through $\mathcal{O}(α_s^2)$. The short-distance coefficients are obtained as series expansions in $r=\frac{4m_c^2}{s}$ around $r=0, 1/3, 2/3, 1$, using the method of differential equations. By combining the expansions from all four points, we construct composite asymptotic expressions that reproduce the exact results accurately over the full range $0 \leq r\leq 1$, with relative errors below $0.1\%$ over most of the domain and remaining under $1\%$ elsewhere. Analytic expressions for the leading and next-to-leading logarithmic terms are extracted in the limit $r\to 0$. Using these results, we compute the unpolarized cross sections and observe that the perturbative corrections are small for $χ_{c0}+γ$, moderate for $χ_{c1}+γ$, and substantial for $η_c+γ$ and $χ_{c2}+γ$. Theoretical prediction for $χ_{c1}+γ$ is consistent with the {\tt Belle} measurement within $2σ$, showing good agreement between theory and experiment. We also predict the angular distribution parameters $α^H_θ$, which are insensitive to NRQCD matrix elements and exhibit small theoretical uncertainties. These parameters further display good stability across different perturbative orders. With the high luminosity anticipated at {\tt Belle 2}, future experimental measurements will thus provide a clear test of NRQCD factorization. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2512_04758 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The next-to-next-to-leading-order QCD corrections to $e^+e^-\to η_c/χ_{cJ}+γ$ at B factories Li, Cong Sang, Wen-Long Zhang, Hong-Fei High Energy Physics - Phenomenology High Energy Physics - Experiment We investigate the processes $e^+e^-\to η_c+γ$ and $e^+e^-\to χ_{cJ}+γ$ at B factories within the NRQCD factorization framework, computing the corresponding helicity amplitudes through $\mathcal{O}(α_s^2)$. The short-distance coefficients are obtained as series expansions in $r=\frac{4m_c^2}{s}$ around $r=0, 1/3, 2/3, 1$, using the method of differential equations. By combining the expansions from all four points, we construct composite asymptotic expressions that reproduce the exact results accurately over the full range $0 \leq r\leq 1$, with relative errors below $0.1\%$ over most of the domain and remaining under $1\%$ elsewhere. Analytic expressions for the leading and next-to-leading logarithmic terms are extracted in the limit $r\to 0$. Using these results, we compute the unpolarized cross sections and observe that the perturbative corrections are small for $χ_{c0}+γ$, moderate for $χ_{c1}+γ$, and substantial for $η_c+γ$ and $χ_{c2}+γ$. Theoretical prediction for $χ_{c1}+γ$ is consistent with the {\tt Belle} measurement within $2σ$, showing good agreement between theory and experiment. We also predict the angular distribution parameters $α^H_θ$, which are insensitive to NRQCD matrix elements and exhibit small theoretical uncertainties. These parameters further display good stability across different perturbative orders. With the high luminosity anticipated at {\tt Belle 2}, future experimental measurements will thus provide a clear test of NRQCD factorization. |
| title | The next-to-next-to-leading-order QCD corrections to $e^+e^-\to η_c/χ_{cJ}+γ$ at B factories |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2512.04758 |