Direct lattice QCD calculation of the $\theta$-induced CP-violating pion-nucleon coupling
We present the first direct lattice QCD determination of the $\theta$-induced CP-violating pion-nucleon-nucleon coupling $\tilde g_{\pi NN}$. Using overlap valence fermions on three $2+1$-flavor domain-wall ensembles at a single lattice spacing, we calculate the forward proton matrix element of the isovector pseudoscal...