Method for high-precision determination of the nucleon axial structure using lattice QCD: Removing $πN$-state contamination
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2025
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| author | Aoki, Yasumichi Ishikawa, Ken-Ichi Kuramashi, Yoshinobu Sasaki, Shoichi Sato, Kohei Shintani, Eigo Tsuji, Ryutaro Watanabe, Hiromasa Yamazaki, Takeshi |
| author_facet | Aoki, Yasumichi Ishikawa, Ken-Ichi Kuramashi, Yoshinobu Sasaki, Shoichi Sato, Kohei Shintani, Eigo Tsuji, Ryutaro Watanabe, Hiromasa Yamazaki, Takeshi |
| contents | We performed a precise calculation of physical quantities related to the axial structure of the nucleon using 2+1 flavor lattice QCD gauge configuration (PACS10 configuration) generated at the physical point with lattice volume larger than $(10\;{\mathrm{fm}})^4$ by the PACS Collaboration. The nucleon matrix element of the axial-vector current has two types of the nucleon form factors, the axial-vector ($F_A$) form factor and the induced pseudoscalar ($F_P$) form factor. Recently lattice QCD simulations have succeeded in reproducing the experimental value of the axial-vector coupling, $g_A$, determined from $F_A(q^2)$ at zero momentum transfer $q^2=0$, at a percent level of statistical accuracy. However, the $F_P$ form factor so far has not reproduced the experimental values well due to strong $πN$ excited-state contamination. Therefore, we proposed a simple subtraction method for removing the so-called leading $πN$-state contribution, and succeeded in reproducing the values obtained by two experiments of muon capture on the proton and pion electro-production for $F_P(q^2)$. The novel approach can also be applied to the nucleon pseudoscalar matrix element to determine the pseudoscalar ($G_P$) form factor with the help of the axial Ward-Takahashi identity. The resulting form factors, $F_P(q^2)$ and $G_P(q^2)$, are in good agreement with the prediction of the pion-pole dominance model. In the new analysis, the induced pseudoscalar coupling $g_P^\ast$ and the pion-nucleon coupling $g_{πNN}$ can be evaluated with a few percent accuracy including systematic uncertainties using existing data calculated at two lattice spacings. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_06854 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Method for high-precision determination of the nucleon axial structure using lattice QCD: Removing $πN$-state contamination Aoki, Yasumichi Ishikawa, Ken-Ichi Kuramashi, Yoshinobu Sasaki, Shoichi Sato, Kohei Shintani, Eigo Tsuji, Ryutaro Watanabe, Hiromasa Yamazaki, Takeshi High Energy Physics - Lattice High Energy Physics - Phenomenology We performed a precise calculation of physical quantities related to the axial structure of the nucleon using 2+1 flavor lattice QCD gauge configuration (PACS10 configuration) generated at the physical point with lattice volume larger than $(10\;{\mathrm{fm}})^4$ by the PACS Collaboration. The nucleon matrix element of the axial-vector current has two types of the nucleon form factors, the axial-vector ($F_A$) form factor and the induced pseudoscalar ($F_P$) form factor. Recently lattice QCD simulations have succeeded in reproducing the experimental value of the axial-vector coupling, $g_A$, determined from $F_A(q^2)$ at zero momentum transfer $q^2=0$, at a percent level of statistical accuracy. However, the $F_P$ form factor so far has not reproduced the experimental values well due to strong $πN$ excited-state contamination. Therefore, we proposed a simple subtraction method for removing the so-called leading $πN$-state contribution, and succeeded in reproducing the values obtained by two experiments of muon capture on the proton and pion electro-production for $F_P(q^2)$. The novel approach can also be applied to the nucleon pseudoscalar matrix element to determine the pseudoscalar ($G_P$) form factor with the help of the axial Ward-Takahashi identity. The resulting form factors, $F_P(q^2)$ and $G_P(q^2)$, are in good agreement with the prediction of the pion-pole dominance model. In the new analysis, the induced pseudoscalar coupling $g_P^\ast$ and the pion-nucleon coupling $g_{πNN}$ can be evaluated with a few percent accuracy including systematic uncertainties using existing data calculated at two lattice spacings. |
| title | Method for high-precision determination of the nucleon axial structure using lattice QCD: Removing $πN$-state contamination |
| topic | High Energy Physics - Lattice High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2505.06854 |