Nucleon Charges from 2+1+1-flavor HISQ and 2+1-flavor clover lattices

Abstract

Precise estimates of the nucleon charges $g_A$, $g_S$ and $g_T$ are needed in many phenomenological analyses of SM and BSM physics. In this talk, we present results from two sets of calculations using clover fermions on 9 ensembles of 2+1+1-flavor HISQ and 4 ensembles of 2+1-flavor clover lattices. We show that high statistics can be obtained cost-effectively using the truncated solver method with bias correction and the coherent source sequential propagator technique. By performing simulations at 4--5 values of the source-sink separation $t_{\mathrm{sep}}$, we demonstrate control over excited-state contamination using 2- and 3-state fits. Using the high-precision 2+1+1-flavor data, we perform a simultaneous fit in $a$, $M_{\pi }$ and $M_{\pi }L$ to obtain our final results for the charges.

Comments: Proceedings of the 34th annual International Symposium on Lattice Field Theory, 24-30 July 2016, University of Southampton, UK