2020/01/30 by Yong-Chull Jang, Jang, Yong-Chull, Rajan Gupta +9
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Lattice (hep-lat) #Particle physics theoretical and experimental studies #Physics of Superconductivity and Magnetism #Quantum Chromodynamics and Particle Interactions
paper · pdf · doi:10.48550/arxiv.2001.11592
openalex publication_date 2020/01/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The nucleon axial form factors -- axial GA, induced pseudoscalar \widetildeGP and pseudoscalar GP -- have displayed large systematics in lattice QCD calculations. The major symptoms were the violation of the partially conserved axial current (PCAC) relation between the three form factors, and the underestimation of the induced pseudoscalar coupling gP^∗ and the axial charge radius rA compared to phenomenological estimates. The small gP^∗ was a consequence of the failure of the pion-pole dominance (PPD) hypothesis, especially at low Mπ2. The small charge radius rA and the underestimate of gA were related. The dominant systematic responsible is the lack of inclusion of low-energy (N π) states that are not manifest in the multiexponential fit to the nucleon two-point correlator. We show that this low-energy state can be determined from the three-point correlator ⟨ N A4 N ⟩ with the insertion of the temporal component of the axial current A4 within the nucleon state, ie, the strategy labeled SA4 [1]. Including this low-energy state in fits to control excited-state contamination (ESC) gives results for gA, rA, and gP^∗ that are consistent with experimental/phenomenological values. However, the systematic uncertainties, especially in data at small Q2, are now much larger.