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Isovector axial form factors of the nucleon in two-flavor lattice QCD

PRISMA Cluster of Excellence and Institut für Kernphysik, University of Mainz, Johann-Joachim-Becher-Weg 45, 55099 Mainz, Germany

Helmholtz Institute Mainz, University of Mainz, 55099 Mainz, Germany

Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany

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M. Della Morte

CP³-Origins & Danish IAS, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

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D. Djukanovic

PRISMA Cluster of Excellence and Institut für Kernphysik, University of Mainz, Johann-Joachim-Becher-Weg 45, 55099 Mainz, Germany

Helmholtz Institute Mainz, University of Mainz, 55099 Mainz, Germany

E-mail Address: d.djukanovic@him.uni-mainz.de

Corresponding author.

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G. M. von Hippel

PRISMA Cluster of Excellence and Institut für Kernphysik, University of Mainz, Johann-Joachim-Becher-Weg 45, 55099 Mainz, Germany

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J. Hua

PRISMA Cluster of Excellence and Institut für Kernphysik, University of Mainz, Johann-Joachim-Becher-Weg 45, 55099 Mainz, Germany

Helmholtz Institute Mainz, University of Mainz, 55099 Mainz, Germany

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B. Jäger

CP³-Origins & Danish IAS, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark

Department of Physics, College of Science, Swansea University, Swansea SA2 8PP, UK

ETH Zürich, Institute for Theoretical Physics, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland

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P. M. Junnarkar

Helmholtz Institute Mainz, University of Mainz, 55099 Mainz, Germany

Tata Institute of Fundamental Research (TIFR), Homi Bhabha, Mumbai 400005, India

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H. B. Meyer

PRISMA Cluster of Excellence and Institut für Kernphysik, University of Mainz, Johann-Joachim-Becher-Weg 45, 55099 Mainz, Germany

Helmholtz Institute Mainz, University of Mainz, 55099 Mainz, Germany

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T. D. Rae

PRISMA Cluster of Excellence and Institut für Kernphysik, University of Mainz, Johann-Joachim-Becher-Weg 45, 55099 Mainz, Germany

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H. Wittig

PRISMA Cluster of Excellence and Institut für Kernphysik, University of Mainz, Johann-Joachim-Becher-Weg 45, 55099 Mainz, Germany

Helmholtz Institute Mainz, University of Mainz, 55099 Mainz, Germany

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https://doi.org/10.1142/S0217751X1950009XCited by:51 (Source: Crossref)

Abstract

We present a lattice calculation of the nucleon isovector axial and induced pseudoscalar form factors on the CLS ensembles using $N_{f} = 2$ dynamical flavors of nonperturbatively $𝒪 (a)$ -improved Wilson fermions and an $𝒪 (a)$ -improved axial current together with the pseudoscalar density. Excited-state effects in the extraction of the form factors are treated using a variety of methods, with a detailed discussion of their respective merits. The chiral and continuum extrapolation of the results is performed both using formulae inspired by Heavy Baryon Chiral Perturbation Theory (HBChPT) and a global approach to the form factors based on a chiral effective field theory (EFT) including axial vector mesons. Our results indicate that careful treatment of excited-state effects is important in order to obtain reliable results for the axial form factors of the nucleon, and that the main remaining error stems from the systematic uncertainties of the chiral extrapolation. As final results, we quote $g_{A} = 1.278 \pm 0.06 8_{- 0.087}^{+ 0.000}$ , $〈 r_{A}^{2} 〉 = 0.360 \pm 0.03 6_{- 0.088}^{+ 0.080} {fm}^{2}$ , and $g_{P} = 7.7 \pm 1 . 8_{- 2.0}^{+ 0.8}$ for the axial charge, axial charge radius and induced pseudoscalar charge, respectively, where the first error is statistical and the second is systematic.