Nucleon isovector couplings in Nf = 2 + 1 lattice QCD at the physical point

Ryutaro Tsuji; Natsuki Tsukamoto; Yasumichi Aoki; Ken-Ichi Ishikawa; Yoshinobu Kuramashi; Shoichi Sasaki; Eigo Shintani; Takeshi Yamazaki

doi:10.1103/PhysRevD.106.094505

paper

Nucleon isovector couplings in Nf = 2 + 1 lattice QCD at the physical point

arXiv:2207.11914 · doi:10.1103/PhysRevD.106.094505

Abstract

We present results for the scalar and tensor isovector-couplings ( $g_{S}$ and $g_{T}$ ) of the nucleon measured at the physical point ( $M_{π} = 135$ MeV) with a single lattice spacing of $0.085 fm$ in 2+1 flavor QCD. Our calculations are carried out with two ensembles of gauge configurations generated by the PACS Collaboration with nonperturbatively $O (a)$ improved Wilson quark action and Iwasaki gauge action on $(10.9 fm)^{4}$ and $(5.5 fm)^{4}$ lattices, where the finite-size effect on the nucleon mass was not shown at the level of the statistical precision less than 0.5%. We compute the nucleon three-point correlation functions in the vector, axial, scalar, and tensor channels. We confirm that our previous result of the nucleon axial coupling on the large spatial volume of $(10.9 fm)^{4}$ has no finite-size effect at the level of the statistical precision of 1.9%. For the renormalization, we first renormalize $g_{S}$ and $g_{T}$ nonperturbatively using the RI/SMOM $_{(γ_{μ})}$ scheme, a variant of Rome-Southampton RI/MOM scheme with reduced systematic errors, as the intermediate scheme. We evaluate our final results at the renormalization scale of 2 GeV in the $MS$ scheme through matching procedure between the RI/SMOM $_{(γ_{μ})}$ and $MS$ schemes with the help of perturbation theory, and then obtain $g_{S} = 0.927 (71)_{stat} (22)_{syst}$ and $g_{T} = 1.036 (6)_{stat} (20)_{syst}$ .

52 pages, 11 figures

Nucleon isovector couplings in Nf = 2 + 1 lattice QCD at the physical point

Abstract

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