Towards NNLO QCD predictions for off-shell top-quark pair production and decays
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| Format: | Preprint |
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2025
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| _version_ | 1866911058733563904 |
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| author | Buonocore, Luca Grazzini, Massimiliano Kallweit, Stefan Lindert, Jonas M. Savoini, Chiara |
| author_facet | Buonocore, Luca Grazzini, Massimiliano Kallweit, Stefan Lindert, Jonas M. Savoini, Chiara |
| contents | We consider QCD radiative corrections to $W^+W^-b {\bar b}$ production with leptonic decays and massive bottom quarks at the LHC. We perform an exact next-to-leading order (NLO) calculation within the $q_T$-subtraction formalism and validate it against an independent computation in the dipole subtraction scheme. Non-resonant and off-shell effects related to the top quarks and the leptonic decays of the $W^\pm$ bosons are consistently included. We also consider the approximation in which the real-emission contribution is computed exactly while the virtual is evaluated in the double-pole approximation (DPA), which formally requires the inclusion of both factorisable and non-factorisable corrections. We evaluate such contributions and show that the DPA performs remarkably well at both the inclusive and differential levels. We then extend our calculation to the next-to-next-to-leading order (NNLO). All tree-level and one-loop amplitudes are evaluated exactly, while the missing two-loop virtual contribution is estimated using the DPA. The factorisable two-loop corrections are explicitly computed by relying on available results for the polarised two-loop on-shell top-quark pair production amplitudes and the corresponding top-quark decays. The non-factorisable contributions are inferred by exploiting the cancellation of logarithmic singularities in the $Γ_t\to 0$ limit through an on-shell matching procedure. The NNLO corrections for the inclusive cross section are found to increase the NLO prediction by approximately $11\%$, with a numerical uncertainty that is conservatively estimated to be below the $2\%$ level $\unicode{x2013}$ significantly smaller than the $5\%$ residual perturbative uncertainties. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_11410 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Towards NNLO QCD predictions for off-shell top-quark pair production and decays Buonocore, Luca Grazzini, Massimiliano Kallweit, Stefan Lindert, Jonas M. Savoini, Chiara High Energy Physics - Phenomenology High Energy Physics - Experiment We consider QCD radiative corrections to $W^+W^-b {\bar b}$ production with leptonic decays and massive bottom quarks at the LHC. We perform an exact next-to-leading order (NLO) calculation within the $q_T$-subtraction formalism and validate it against an independent computation in the dipole subtraction scheme. Non-resonant and off-shell effects related to the top quarks and the leptonic decays of the $W^\pm$ bosons are consistently included. We also consider the approximation in which the real-emission contribution is computed exactly while the virtual is evaluated in the double-pole approximation (DPA), which formally requires the inclusion of both factorisable and non-factorisable corrections. We evaluate such contributions and show that the DPA performs remarkably well at both the inclusive and differential levels. We then extend our calculation to the next-to-next-to-leading order (NNLO). All tree-level and one-loop amplitudes are evaluated exactly, while the missing two-loop virtual contribution is estimated using the DPA. The factorisable two-loop corrections are explicitly computed by relying on available results for the polarised two-loop on-shell top-quark pair production amplitudes and the corresponding top-quark decays. The non-factorisable contributions are inferred by exploiting the cancellation of logarithmic singularities in the $Γ_t\to 0$ limit through an on-shell matching procedure. The NNLO corrections for the inclusive cross section are found to increase the NLO prediction by approximately $11\%$, with a numerical uncertainty that is conservatively estimated to be below the $2\%$ level $\unicode{x2013}$ significantly smaller than the $5\%$ residual perturbative uncertainties. |
| title | Towards NNLO QCD predictions for off-shell top-quark pair production and decays |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2507.11410 |