Nucleon isovector charges and twist-2 matrix elements with Nf=2+1 dynamical Wilson quarks

We present results from a lattice QCD study of nucleon matrix elements at vanishing momentum transfer for local and twist-2 isovector operator insertions. Computations are performed on gauge ensembles with nonperturbatively improved N-f =2 + 1 Wilson fermions, covering four values of the lattice spacing and pion masses down to M-pi approximate to 200 MeV. Several source-sink separations (typically similar to 1.0 to similar to 1.5 fm) allow us to assess excited-state contamination. Results on individual ensembles are obtained from simultaneous two-state fits across all observables and all available source-sink separations with the energy gap as a common fit parameter. Renormalization has been performed nonperturbatively using the Rome-Southampton method for all but the finest lattice spacing for which an extrapolation has been used. Physical results are quoted in the (MS) over bar scheme at a scale of mu = 2 GeV and are obtained from a combined chiral, continuum, and finite-size extrapolation. For the nucleon isovector axial, scalar, and tensor charges we find physical values of g(A)(u-d) = 1.242(25)(stat)((+00)(-31))sys, g(S)(u-d) = 1.13(11)(stat)((+07)(-06))sys and g(T)(u-d) = 0.965 (38)(stat)((+13)(-41))sys, respectively, where individual systematic errors in each direction from the chiral, continuum, and finite-size extrapolation have been added in quadrature. Our final results for the isovector average quark momentum fraction and the isovector helicity and transversity moments are given by < x >(u-d) = 0.180(25)(stat)((+14)(-06))sys, < x >(Delta u-Delta d) = 0.221(25)(stat)((+10)(-00))sys and < x >delta u-delta d = 0.212(32)(stat)((+20)(-10))sys, respectively.