Strange electromagnetic form factors of the nucleon with $N_f=2+1$ $\mathcal{O}(a)$-improved Wilson fermions

Abstract

We present results for the strange contribution to the electromagnetic form factors of the nucleon computed on the CLS ensembles with $N_f=2+1$ flavors of $\mathcal{O}(a)$-improved Wilson fermions and an $\mathcal{O}(a)$-improved vector current. Several source-sink separations are investigated in order to estimate the excited-state contamination. We calculate the form factors on six ensembles with lattice spacings in the range of $a=0.049-0.086\text{fm}$ and pion masses in the range of $m_{\pi }=200-360\text{MeV}$, which allows for a controlled chiral and continuum extrapolation. In the computation of the quark-disconnected contributions we employ hierarchical probing as a variance reduction technique.

Comments: 23 pages, 9 figures; matching version accepted for publication in PRL