Mass and isovector matrix elements of the nucleon at zero-momentum transfer

Abstract

We present the current status of our analysis of nucleon structure observables including isovector charges and twist-2 matrix elements as well as the nucleon mass. Results are computed on a large set of CLS $N_f=2+1$ gauge ensembles with $M_{\pi }\approx 0.130\mathrm{MeV}\dots 350\mathrm{MeV}$, four values of the lattice spacing $a=0.05\mathrm{fm}\dots 0.09\mathrm{fm}$ and covering a large range of physical volumes. Compared to the results presented at last year's conference we have added data on a very fine and large box at small light quark mass ($T\times L^3=192\times 96^3$, $M_{\pi }=172\mathrm{MeV}$, $a=0.05\mathrm{fm}$). Additional (intermediate) source-sink separations have been computed on the coarser ensembles, further increasing effective statistics and allowing for a more fine-grained control in the treatment of the excited-state contamination. Excited states in the nucleon matrix elements are tamed by a simultaneous, two-state fit ansatz using the summation method.

Comments: 10 pages, 4 figures, Talk presented at the 39th International Symposium on Lattice Field Theory, 8th-13th August 2022, Bonn, Germany