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

## TL;DR

This study computes the strange electromagnetic form factors of the nucleon using lattice QCD with $N_f=2+1$ flavors, improved Wilson fermions, and hierarchical probing, providing results that enable controlled chiral and continuum extrapolations.

## Contribution

It presents the first lattice QCD calculation of strange nucleon form factors with multiple ensembles, improved techniques, and systematic error control.

## Key findings

- Results show small strange contributions to nucleon form factors.
- Controlled chiral and continuum extrapolations achieved.
- Hierarchical probing effectively reduces variance in disconnected diagrams.

## 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.