Nucleon axial form factor at large momentum transfers

Chen Chen; Craig D. Roberts

doi:10.1140/epja/s10050-022-00848-x

2024 Impact factor 2.8

Hadrons and Nuclei

Open Access

Eur. Phys. J. A (2022) 58: 206
https://doi.org/10.1140/epja/s10050-022-00848-x

Regular Article - Theoretical Physics

Nucleon axial form factor at large momentum transfers

Chen Chen¹^,2 and Craig D. Roberts³^,4^b

¹ Interdisciplinary Center for Theoretical Study, University of Science and Technology of China, 230026, Hefei, Anhui, China
² Peng Huanwu Center for Fundamental Theory, 230026, Hefei, Anhui, China
³ School of Physics, Nanjing University, 210093, Nanjing, Jiangsu, China
⁴ Institute for Nonperturbative Physics, Nanjing University, 210093, Nanjing, Jiangsu, China

^b cdroberts@nju.edu.cn

Received: 26 June 2022
Accepted: 4 October 2022
Published online: 28 October 2022

Abstract

Using a Poincaré-covariant quark+diquark Faddeev equation and related symmetry-preserving weak interaction current, we deliver parameter-free predictions for the nucleon axialvector form factor, $G_{A} (Q^{2})$ $$G_A(Q^2)$$ , on the domain $0 \leq x = Q^{2} / m_{N}^{2} \leq 10$ $0\le x=Q^2/m_N^2\le 10$ , where $m_{N}$ $$m_N$$ is the nucleon mass. We also provide a detailed analysis of the flavour separation of the proton $G_{A}$ $$G_A$$ into contributions from valence u and d quarks; and with form factors available on such a large $Q^{2}$ $$Q^2$$ domain, predictions for the flavour-separated axial-charge light-front transverse spatial density profiles. Our calculated axial charge ratio $g_{A}^{d} / g_{A}^{u} = - 0.32 (2)$ $$g_A^d/g_A^u=-0.32(2)$$ is consistent with available experimental data and markedly larger in magnitude than the value typical of nonrelativistic quark models. The value of this ratio is sensitive to the strength of axialvector diquark correlations in the Poincaré-covariant nucleon wave function. Working with a realistic axialvector diquark content, the d and u quark transverse density profiles are similar. Some of these predictions could potentially be tested with new data on threshold pion electroproduction from the proton at large $Q^{2}$ $$Q^2$$ .

© The Author(s) 2022

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.