Isoscalar electromagnetic form factors of the nucleon in $N_{\mathrm{f}}=2+1$ lattice QCD

Abstract

We present results for the isoscalar electromagnetic form factors of the nucleon computed on the Coordinated Lattice Simulations (CLS) ensembles with $N_{\mathrm{f}}=2+1$ flavors of $\mathcal{O}(a)$-improved Wilson fermions and an $\mathcal{O}(a)$-improved conserved vector current. In order to estimate the excited-state contamination, we employ several source-sink separations and apply the summation method. For the computation of the quark-disconnected diagrams, a stochastic estimation based on the one-end trick is performed, in combination with a frequency-splitting technique and the hopping parameter expansion. By these means, we obtain a clear signal for the form factors including the quark-disconnected contributions, which have a statistically significant effect on our results.

Comments: 9 pages, 5 figures, contribution to the 38th International Symposium on Lattice Field Theory (LATTICE21), 26th-30th July 2021, Zoom/Gather@Massachusetts Institute of Technology; enlarged font size in figures