Speaker
Description
We present the results of the nucleon helicity moments and generalized form factors in the isovector and isoscalar channels computed within lattice QCD. We analyzed four ensembles with $N_f=2+1+1$ twisted mass clover-improved fermions with the mass of the quarks tuned to their physical mass. The four ensembles have lattice spacings approximately $a=0.05 \,\text{fm}, 0.06 \,\text{fm}, 0.07 \,\text{fm}, 0.08 \,\text{fm}$ that allow us to obtain results at the continuum limit directly at physical pion mass. We computed axial-vector generalized form factors as a function of momentum transfer square $Q^2$. We study the $Q^2$ dependence of the GFFs using the dipole ansatz and model-independent $z-$expansion. We find the nucleon isovector helicity moment $\langle x\rangle_{\Delta u-\Delta d} = 0.1871(82)$ and isoscalar helicity moment $\langle x \rangle_{\Delta u+\Delta d} = 0.1186(60)$