Iso-vector axial form factors of the nucleon in two-flavour lattice QCD

Preprint number: CP3-Origins-2017-18 DNRF90
Authors: Michele Della Morte (CP3-Origins & DIAS) and et al. (various)

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We present a lattice calculation of the nucleon iso-vector axial and induced pseudoscalar form
factors on the CLS ensembles using Nf = 2 dynamical flavours of non-perturbatively O(a)-improved Wilson fermions and an O(a)-improved axial current together with the pseudoscalar
density. Excited-state effects on 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 HBChPT-inspired formulae and an EFT-based global approach to the form
factors from a chiral effective theory 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.