  Renormalization conditions imposed on quark bilinear vertex functions in the
conventional RI/MOM scheme use exceptional momentum configurations. With
practical values for the lattice cutoff, these vertex functions are
contaminated with unwanted low energy physics (pion pole, zero modes, etc),
which is a large source of systematic error. These effects can be reduced by
using non-exceptional momenta. We discuss the quark mass renormalization with
non-exceptional momenta using 2+1 flavor domain wall fermions based on a
recently proposed RI/SMOM scheme.
