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Title: 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 $$\bar{MS}$$, $$g_1$$, $MOM$ 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. Lastly, 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.
ORCiD logo [1] ;  [2] ;  [3]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Univ. of Costa Rica, San Pedro (Costa Rica)
Publication Date:
OSTI Identifier:
Report Number(s):
JLAB-PHY-16-2198; SLAC-PUB-16449; DOE/OR/23177-3646; arXiv:1601.06568
Journal ID: ISSN 0370-2693; PII: S037026931630048X
Grant/Contract Number:
AC05-06OR23177; AC02-76SF00515; SLAC-PUB-16449
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Name: Physics Letters. Section B; Journal ID: ISSN 0370-2693
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States