dorsal/arxiv
View SchemaLattice QCD determination of the $\gamma Z$ box contribution to the proton weak charge
| Authors | Zhao-long Zhang, Xu Feng, Mikhail Gorchtein, Lu-Chang Jin, Chuan Liu, Chien-Yeah Seng |
|---|---|
| Categories | |
| ArXiv ID | 2601.06582vv1 |
| URL | https://arxiv.org/abs/2601.06582 |
| License | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
Abstract
We present the first lattice QCD determination of the $\gamma Z$ box contribution to parity-violating electron-proton scattering, $\square_{\gamma Z}$ , 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 $\square_{\gamma Z}= 0.00412(9)$ , 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 $\square_{\gamma Z}$ 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 $Q_{W}^p$.
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"abstract": "We present the first lattice QCD determination of the $\\gamma Z$ box contribution to parity-violating electron-proton scattering, $\\square_{\\gamma Z}$ , 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 $\\square_{\\gamma Z}= 0.00412(9)$ , 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 $\\square_{\\gamma Z}$ 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 $Q_{W}^p$.",
"arxiv_id": "2601.06582",
"authors": [
"Zhao-long Zhang",
"Xu Feng",
"Mikhail Gorchtein",
"Lu-Chang Jin",
"Chuan Liu",
"Chien-Yeah Seng"
],
"categories": [
"hep-lat",
"hep-ph",
"nucl-th"
],
"license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
"title": "Lattice QCD determination of the $\\gamma Z$ box contribution to the proton weak charge",
"url": "https://arxiv.org/abs/2601.06582",
"version": "v1"
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