Nucleon axial-vector and pseudoscalar form factors, and PCAC relations

2021/03/31 by Chen Chen, Christian S. Fischer, Craig D. Roberts +1 · 32 citations
Mathematics · Physics and Astronomy · #Coupling constant #Diquark #Form factor (electronics) #High-Energy Particle Collisions Research #Mathematics #Meson #Nuclear physics #Nucleon #Particle physics #Particle physics theoretical and experimental studies #Physics #Pion #Pointwise #Pseudoscalar #Pseudovector #Quantum Chromodynamics and Particle Interactions #Quantum mechanics #Quark #hep-ph

paper · pdf · open access · doi:10.1103/physrevd.105.094022

published in Physical review. D/Physical review. D. 105(9) (American Physical Society) · 27 pages, 13 figures, 1 table

arxiv created 2022/04/03 · openalex publication_date 2022/05/20 · arxiv updated 2022/06/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06

Abstract

We use a continuum quark+diquark approach to the nucleon bound-state problem in relativistic quantum field theory to deliver parameter-free predictions for the nucleon axial and induced pseudoscalar form factors, G_A and G_P, and unify them with the pseudoscalar form factor G₅ or, equivalently, the pion-nucleon form factor G_πNN. We explain how partial conservation of the axial-vector current and the associated Goldberger-Treiman relation are satisfied once all necessary couplings of the external current to the building blocks of the nucleon are constructed consistently; in particular, we fully resolve the seagull couplings to the diquark-quark vertices associated with the axial-vector and pseudoscalar currents. Among the results we describe, the following are worth highlighting. A dipole form factor defined by an axial charge g_A=G_A(0)=1.25(3) and a mass-scale M_A = 1.23(3) m_N, where m_N is the nucleon mass, can accurately describe the pointwise behaviour of G_A. Concerning G_P, we obtain the pseudoscalar charge g_p^∗ = 8.80(23), and find that the pion pole dominance approach delivers a reliable estimate of the directly computed result. Our computed value of the pion-nucleon coupling constant, g_πNN/m_N =14.02(33)/\rm GeV is consistent with recent precision determinations.

Citations

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