Effective charge from lattice QCD

Abstract

Using lattice configurations for quantum chromodynamics (QCD) generated with three domain-wall fermions at a physical pion mass, we obtain a parameter-free prediction of QCD’s renormalisation-group-invariant process-Independent effective chargee, Owing to the dynamical breaking of scale invariance, evident in the emergence of a gluon mass-scale, Amongst other things: ˆ(k2) ˆ(k2) m0 043(1) GeV, this coupling saturates at infrared momenta: ˆ(0) 097(4) . is almost identical to the process-dependent (PD) effective charge defined via the Bjorken sum rule; and also that PD charge which, employed in the one-loop evolution equations, delivers agreement between pion parton distribution functions computed at the hadronic scale and experiment. The diversity of unifying roles played by ˆ(k2) suggests that it is a strong candidate for that object which represents the interaction strength in QCD at any given momentum scale; and its properties support a conclusion that QCD is a mathematically welldefined quantum field theory in four dimensions. Keywords: running coupling, quantum chromodynamics, Dyson-Schwinger equations, lattice field theory, emergence of mass, confinement