Hadronic Parity Violation from 4-quark Interactions

Abstract: We present an exploratory investigation of the parity odd $\Delta I = 1$ pion-nucleon coupling $h_\pi^1$ from lattice QCD. Based on the PCAC relation, we study the parity-conserving effective Hamiltonian and extract the coupling by determining the nucleon mass splitting arising from the effective 4-quark interactions using the Feynman-Hellmann theorem. We present preliminary results of the mass shift for a $32^3 \times 64$ ensemble of $N_f = 2 + 1 + 1$ twisted mass fermions at pion mass $260$ MeV and lattice spacing $a = 0.097$ fm.