Connection between the high energy-scale evolution of the P- and T-odd $\pi N N$ coupling constant and the strong $\pi N N$ interaction

Abstract

The large energy-scale behaviour of the parity and time-reversal violating (PTV) pion-nucleon coupling constant is analyzed in a model combining renormalization-group techniques and the dressing of the PTV vertex with a pion loop. With the strong $\pi N N$ vertex as a mixture of the pseudovector and pseudoscalar couplings, we show that depending on the admixture parameter, two qualitatively distinct types of behaviour are obtained for the PTV coupling constant at high energy scales: an asymptotic freedom or a fixed-point. We find a critical value of the admixture parameter which delineates these two scenarios. Several examples of the high-energy scale behaviour of the PTV $\pi N N$ constant are considered, corresponding to realistic hadronic models of the strong pion-nucleon interaction.