Nucleon structure functions with domain wall fermions

TL;DR

This paper reports a lattice QCD calculation of nucleon structure function moments using domain wall fermions, achieving precise ratios consistent with experiment and providing insights into operator mixing and tensor charge.

Contribution

It demonstrates the advantages of domain wall fermions in accurately determining nucleon structure ratios and reducing operator mixing in lattice QCD calculations.

Findings

The ratio of flavor non-singlet momentum to helicity distribution agrees with experiment.

Chiral symmetry helps eliminate mixing of certain operators.

The isovector tensor charge is calculated as 1.192(30).

Abstract

We present a quenched lattice QCD calculation of the first few moments of the polarized and un-polarized structure functions of the nucleon. Our calculations are done using domain wall fermions and the DBW2 gauge action with inverse lattice spacing ~1.3GeV, physical volume approximatelly (2.4 fm)^3, and light quark masses down to about 1/4 the strange quark mass. Values of the individual moments are found to be significantly larger than experiment, as in past lattice calculations, but interestingly the chiral symmetry of domain wall fermions allows for a precise determination of the ratio of the flavor non-singlet momentum fraction to the helicity distribution, which is in very good agreement with experiment. We discuss the implications of this result. Next, we show that the chiral symmetry of domain wall fermions is useful in eliminating mixing of power divergent lower dimensional operators with twist-3 operators. Finally, we find the isovector tensor charge at renormalization scale 2 GeV in the MS bar scheme to be 1.192(30), where the error is the statistical error only.