On the interface between perturbative and nonperturbative QCD

The QCD running coupling alpha(s)(Q(2)) sets the strength of the interactions of quarks and gluons as a function of the momentum transfer Q. The Q(2) dependence of the coupling is required to describe hadronic interactions at both large and short distances. In this article we adopt the light-front holographic approach to strongly-coupled QCD, a formalism which incorporates confinement, predicts the spectroscopy of hadrons composed of light quarks, and describes the low-Q(2) analytic behavior of the strong coupling alpha(s)(Q(2)). The high-Q(2) dependence of the coupling alpha(s)(Q(2)) is specified by perturbative QCD and its renormalization group equation. The matching of the high and low Q(2) regimes of alpha(s)(Q(2)) then determines the scale Q(0) which sets the interface between perturbative and nonperturbative hadron dynamics. The value of Q(0) can be used to set the factorization scale for DGLAP evolution of hadronic structure functions and the ERBL evolution of distribution amplitudes. We discuss the scheme-dependence of the value of Q(0) and the infrared fixed-point of the QCD coupling. Our analysis is carried out for the (MS) over bar, g(1), MOM and V renormalization schemes. Our results show that the discrepancies on the value of alpha(s) at large distance seen in the literature can be explained by different choices of renormalization schemes. We also provide the formulae to compute alpha(s)(Q(2)) over the entire range of space-like momentum transfer for the different renormalization schemes discussed in this article. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).