Exploring a new approach to hadronic parity violation from lattice QCD

Abstract

The long-range, parity-odd nucleon interaction generated by single-pion exchange is captured in the parity-odd pion–nucleon coupling hπ1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h^{1}_{\\pi }$$\\end{document}. Its calculation in lattice QCD requires the evaluation of four-quark operator nucleon three-point functions. We investigate a new numerical approach to compute hπ1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h^{1}_{\\pi }$$\\end{document} based on nucleon matrix elements of parity-even four-quark operators and related to the parity-violating electroweak theory by partial conservation of axial current (PCAC) and chiral perturbation theory. This study is performed with 2+1+1 dynamical flavors of twisted mass fermions at pion mass mπ≈260MeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_{\\pi } \\approx 260 \\,\ ext {MeV}$$\\end{document} in a lattice box of L≈3fm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$L \\approx 3 \\,\ ext {fm}$$\\end{document} and with lattice spacing of a≈0.091fm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$a \\approx 0.091 \\,\ ext {fm}$$\\end{document}. From a calculation excluding fermion loop diagrams we find a bare coupling of hπ1=8.08(98)·10-7\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$h^{1}_{\\pi }= 8.08 \\,(98) \\cdot 10^{-7}$$\\end{document}.