The generalized schemeindependent Crewther relation in QCD
The Principle of Maximal Conformality (PMC) provides a systematic way to set the renormalization scales orderbyorder for any perturbative QCD calculable processes. The resulting predictions are independent of the choice of renormalization scheme, a requirement of renormalization group invariance. The Crewther relation, which was originally derived as a consequence of conformally invariant field theory, provides a remarkable connection between two observables when the β function vanishes: one can show that the product of the Bjorken sum rule for spindependent deep inelastic lepton–nucleon scattering times the Adler function, defined from the cross section for electron–positron annihilation into hadrons, has no pQCD radiative corrections. The “Generalized Crewther Relation” relates these two observables for physical QCD with nonzero β function; specifically, it connects the nonsinglet Adler function (D ^{ns}) to the Bjorken sum rule coefficient for polarized deepinelastic electron scattering (C _{Bjp}) at leading twist. A schemedependent Δ _{CSB}term appears in the analysis in order to compensate for the conformal symmetry breaking (CSB) terms from perturbative QCD. In conventional analyses, this normally leads to unphysical dependence in both the choice of the renormalization scheme and the choice of the initial scale at any finite order. However, by applying PMC scalesetting, we can fix the scales of the QCD coupling unambiguously at every order of pQCD. The result is that both D ^{ns} and the inverse coefficient C$$1\atop{Bjp}$$ have identical pQCD coefficients, which also exactly match the coefficients of the corresponding conformal theory. Thus one obtains a new generalized Crewther relation for QCD which connects two effective charges, $$\hat{α}$$ _{d}(Q)=Σ _{i≥1}$$\hat{α}^i\atop{g1}$$(Qi), at their respective physical scales. This identity is independent of the choice of the renormalization scheme at any finite order, and the dependence on the choice of the initial scale is negligible. Lastly, similar scalefixed commensurate scale relations also connect other physical observables at their physical momentum scales, thus providing conventionindependent, fundamental precision tests of QCD.
 Authors:

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^{[3]}
 Chongqing Univ. (China). Dept. of Physics
 Univ. of Pittsburgh, PA (United States). Dept. of Physics and Astronomy
 SLAC National Accelerator Lab., Menlo Park, CA (United States)
 Publication Date:
 Report Number(s):
 SLACPUB16845
Journal ID: ISSN 03702693; PII: S0370269317303830
 Grant/Contract Number:
 11625520; 11275280; AC0276SF00515
 Type:
 Accepted Manuscript
 Journal Name:
 Physics Letters. Section B
 Additional Journal Information:
 Journal Volume: 770; Journal Issue: C; Journal ID: ISSN 03702693
 Publisher:
 Elsevier
 Research Org:
 SLAC National Accelerator Lab., Menlo Park, CA (United States)
 Sponsoring Org:
 USDOE Office of Science (SC), High Energy Physics (HEP) (SC25); National Natural Science Foundation of China (NNSFC)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
 OSTI Identifier:
 1373120