Speaker
Description
We present our progress on the computation of the axial form factor of the nucleon with flavour structure $u+d-2s$ from lattice QCD. We employ a set of $N_f=2+1$ CLS ensembles with O(a)-improved Wilson fermions and the Lüscher-Weisz gauge action, with lattice spacings ranging from 0.05 fm to 0.086 fm and pion masses spanning between 130 MeV and 350 MeV.
We employ multiple source-sink separations and use the summation method to suppress the contamination from excited states. We use a z-expansion on each ensemble to parametrize the $Q^2$-dependence of the form factor and simultaneously fit the available source-sink separation for all $Q^2<=0.7\, {\rm GeV}^2$. We outline our analysis of the stability of the fits under different ansätze and different estimations of the covariance matrix and report on our strategy for a comprehensive determination of the physical form factor.
