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

Abstract

We report the first lattice QCD result of the axial charge of N(1535), $g_A^{N^{\ast }{N}^{\ast }}$. 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 $g_A^{N^{\ast }{N}^{\ast }}\sim 0.2$, independent of quark masses, in the pion-mass range of 0.7 to 1.1 GeV.

Comments: proceedings of the 11th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon September 10-14, 2007 IKP, Forschungzentrum Juelich, Germany