6533b7d4fe1ef96bd1262d33

RESEARCH PRODUCT

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

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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 Nf=2+1 Wilson fermions, covering four values of the lattice spacing and pion masses down to Mπ≈200 MeV. Several source-sink separations (typically ∼1.0 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¯ scheme at a scale of μ=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 gAu−d=1.242(25)stat(+00−31)sys, gSu−d=1.13(11)stat(+07−06)sys and gTu−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⟩Δu−Δd=0.221(25)stat(+10−00)sys, and ⟨x⟩δu−δd=0.212(32)stat(+20−10)sys, respectively.