Anatomy of the ρ resonance from lattice QCD at the physical point**Supported in part by the U.S. DOE Grant No. DE-SC0013065, the National Nature Science Foundation of China (NSFC) (11335001, 11575196, 11575197, 11621131001) (CRC110 by DFG and NSFC), A. A. is supported in part by the National Science Foundation CAREER (PHY-1151648) and by U.S. DOE (DE-FG02-95ER40907), Y. C. thanks the

Abstract

We propose a strategy to access the component of the ρ resonance in lattice QCD. Through a mixed action formalism (overlap valence on domain wall sea), the energy of the component is derived at different valence quark masses, and shows a linear dependence on . The slope is determined to be , from which the valence sigma term is extracted to be MeV using the Feynman-Hellman theorem. At the physical pion mass, the mass of the component is interpolated to be , which is close to the ρ resonance mass. We also obtain the leptonic decay constant of the component to be , which can be compared with the experimental value through the relation , with being the on-shell wavefunction renormalization of ρ owing to the interaction. We emphasize that and of the component, which are obtained for the first time from QCD, can be taken as the input parameters of ρ in effective field theory studies where ρ acts as a fundamental degree of freedom.