Nucleon Charges, Form-factors and Neutron EDM

Abstract

We present an update of our analysis of statistical and systematic errors in the calculation of iso-vector scalar, axial and tensor charges of the nucleon. The calculations are done using $N_f=2+1+1$ flavor HISQ ensembles generated by the MILC Collaboration at three values of the lattice spacing ($a=0.12,0.09,$ and $0.06$ fm) and three values of the quark mass ($M_{\pi }\approx 310,220$ and $130$ MeV); and clover fermions for calculating the correlation functions, i.e., we use a clover-on-HISQ lattice formulation. The all-mode-averaging method allows us to increase the statistics by a factor of eight for the same computational cost leading to a better understanding of and control over excited state contamination. Our current results, after extrapolation to the continuum limit and physical pion mass are $g_A^{u-d}=1.21(3)$, $g_T^{u-d}=1.005(59)$ and $g_S^{u-d}=0.95(12)$. Further checks of control over all systematic errors, especially in $g_A^{u-d}$, are still being performed. Using results for the flavor-diagonal charges, $g_T^u$, $g_T^d$ and $g_T^s$, we analyze contributions of the quark electric dipole moment to the neutron EDM and the consequences for split SUSY model.

Comments: Talk at Lattice 2015