Lattice QCD determination of the $γZ$ box contribution to the proton weak charge
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arXiv
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| Autori principali: | , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2026
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| _version_ | 1866908757001240576 |
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| author | Zhang, Zhao-long Feng, Xu Gorchtein, Mikhail Jin, Lu-Chang Liu, Chuan Seng, Chien-Yeah |
| author_facet | Zhang, Zhao-long Feng, Xu Gorchtein, Mikhail Jin, Lu-Chang Liu, Chuan Seng, Chien-Yeah |
| contents | We present the first lattice QCD determination of the $γZ$ box contribution to parity-violating electron-proton scattering, $\square_{γZ}$ , a key ingredient for the precise tests of the Standard Model via the proton weak charge. Our calculation covers the electron beam energies up to $E =155 MeV$. For the axial-vector component, we achieve reduced uncertainties across the entire energy range compared with phenomenological estimates. For the vector component, the uncertainties remain slightly larger after continuum extrapolation. At $E = 0$, where the vector part vanishes, we obtain $\square_{γZ}= 0.00412(9)$ , reducing the uncertainty by a factor of $2$ relative to the most precise previous determination. Incorporating this result yields an updated weak charge of $Q_{W}^{p}= 0.06987(50)$ . The calculated energy dependence of $\square_{γZ}$ further provides a first-principles input for the upcoming P2 experiment at Mainz, which will operate at the optimized beam energy of $155 MeV$ to extract $Q_{W}^p$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_06582 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Lattice QCD determination of the $γZ$ box contribution to the proton weak charge Zhang, Zhao-long Feng, Xu Gorchtein, Mikhail Jin, Lu-Chang Liu, Chuan Seng, Chien-Yeah High Energy Physics - Lattice High Energy Physics - Phenomenology Nuclear Theory We present the first lattice QCD determination of the $γZ$ box contribution to parity-violating electron-proton scattering, $\square_{γZ}$ , a key ingredient for the precise tests of the Standard Model via the proton weak charge. Our calculation covers the electron beam energies up to $E =155 MeV$. For the axial-vector component, we achieve reduced uncertainties across the entire energy range compared with phenomenological estimates. For the vector component, the uncertainties remain slightly larger after continuum extrapolation. At $E = 0$, where the vector part vanishes, we obtain $\square_{γZ}= 0.00412(9)$ , reducing the uncertainty by a factor of $2$ relative to the most precise previous determination. Incorporating this result yields an updated weak charge of $Q_{W}^{p}= 0.06987(50)$ . The calculated energy dependence of $\square_{γZ}$ further provides a first-principles input for the upcoming P2 experiment at Mainz, which will operate at the optimized beam energy of $155 MeV$ to extract $Q_{W}^p$. |
| title | Lattice QCD determination of the $γZ$ box contribution to the proton weak charge |
| topic | High Energy Physics - Lattice High Energy Physics - Phenomenology Nuclear Theory |
| url | https://arxiv.org/abs/2601.06582 |