Lattice QCD study of $g_A^{N^*N^*}$ with two flavors of dynamical quarks

TL;DR

This study presents the first lattice QCD calculation of the axial charge of the N(1535) resonance, revealing a small, quark-mass-independent value around 0.2 in a specific pion-mass range.

Contribution

It provides the first lattice QCD determination of the axial charge for N(1535), employing correlation matrix techniques to isolate signals and eliminate contaminations.

Findings

Axial charge of N(1535) is approximately 0.2.

The axial charge is independent of quark mass within the studied range.

Signal contamination from nearby states was successfully mitigated.

Abstract

We report the first lattice QCD result of the axial charge of N(1535), $g_A^{N^*N^*}$. The measurement is performed with two flavors of dynamical quarks employing the renormalization-group improved gauge action at $\beta$=1.95 and the mean-field improved clover quark action with the hopping parameters, $\kappa$=0.1375, 0.1390 and 0.1400. In order to avoid the signal contaminations by N(1650) lying just 100 MeV above N(1535), we construct 2$\times$2 correlation matrices and diagonalize them so that clear signal separation can be found. The wraparound contributions in the correlator, which can be another source of signal contamination, are eliminated by imposing the Dirichlet boundary condition in the temporal direction. We find that the axial charge of N(1535) takes small values as $g_A^{N^*N^*}\sim 0.2$, independent of quark masses, in the pion-mass range of 0.7 to 1.1 GeV.