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Title: The Conformal Template and New Perspectives for Quantum Chromodynamics

Abstract

Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. One can also use conformal symmetry as a template for perturbative QCD predictions where the effects of the nonzero beta function can be systematically included in the scale of the QCD coupling. This leads to fixing of the renormalization scale and commensurate scale relations which relate observables without scale or scheme ambiguity. The results are consistent with the renormalization group and the analytic connection of QCD to Abelian theory at N{sub C} {yields} 0. I also discuss a number of novel phenomenological features of QCD. Initial-more » and .nal-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, di.ractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, nonperturbative antisymmetric sea quark distributions, anomalous heavy quark e.ects, and the unexpected effects of direct higher-twist processes.« less

Authors:
;
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
900589
Report Number(s):
SLAC-PUB-12381
TRN: US0702339
DOE Contract Number:
AC02-76SF00515
Resource Type:
Conference
Resource Relation:
Journal Name: Prog.Theor.Phys.Suppl.167:76-94,2007; Conference: Invited talk at the International Symposium on the Jubilee of the Sakata Models (pnLambda50), Nagoya, Japan, 25-26 Nov 2006
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; APPROXIMATIONS; BARYONS; BREAKDOWN; COLOR; DEEP INELASTIC SCATTERING; DIFFRACTION; HADRONS; MESONS; PHYSICS; PROJECTILES; QUANTUM CHROMODYNAMICS; QUARKS; RENORMALIZATION; SCATTERING AMPLITUDES; SYMMETRY; TARGETS; Phenomenology-HEP,HEPPH, HEPTH

Citation Formats

Brodsky, Stanley J., and /SLAC. The Conformal Template and New Perspectives for Quantum Chromodynamics. United States: N. p., 2007. Web.
Brodsky, Stanley J., & /SLAC. The Conformal Template and New Perspectives for Quantum Chromodynamics. United States.
Brodsky, Stanley J., and /SLAC. Tue . "The Conformal Template and New Perspectives for Quantum Chromodynamics". United States. doi:. https://www.osti.gov/servlets/purl/900589.
@article{osti_900589,
title = {The Conformal Template and New Perspectives for Quantum Chromodynamics},
author = {Brodsky, Stanley J. and /SLAC},
abstractNote = {Conformal symmetry provides a systematic approximation to QCD in both its perturbative and nonperturbative domains. One can use the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories to obtain an analytically tractable approximation to QCD in the regime where the QCD coupling is large and constant. For example, there is an exact correspondence between the fifth-dimensional coordinate of AdS space and a specific impact variable which measures the separation of the quark constituents within the hadron in ordinary space-time. This connection allows one to compute the analytic form of the frame-independent light-front wavefunctions of mesons and baryons, the fundamental entities which encode hadron properties and allow the computation of exclusive scattering amplitudes. One can also use conformal symmetry as a template for perturbative QCD predictions where the effects of the nonzero beta function can be systematically included in the scale of the QCD coupling. This leads to fixing of the renormalization scale and commensurate scale relations which relate observables without scale or scheme ambiguity. The results are consistent with the renormalization group and the analytic connection of QCD to Abelian theory at N{sub C} {yields} 0. I also discuss a number of novel phenomenological features of QCD. Initial- and .nal-state interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, di.ractive hard hadronic reactions, the breakdown of the Lam Tung relation in Drell-Yan reactions, and nuclear shadowing and non-universal antishadowing--leading-twist physics not incorporated in the light-front wavefunctions of the target computed in isolation. I also discuss tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, nonperturbative antisymmetric sea quark distributions, anomalous heavy quark e.ects, and the unexpected effects of direct higher-twist processes.},
doi = {},
journal = {Prog.Theor.Phys.Suppl.167:76-94,2007},
number = ,
volume = ,
place = {United States},
year = {Tue Mar 06 00:00:00 EST 2007},
month = {Tue Mar 06 00:00:00 EST 2007}
}

Conference:
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  • In these lectures I will discuss three central topics in quantum chromodynamics: (1) the use of light cone quantization and Fock space methods to determine the long and short-distance structure of quark and gluon distributions within hadrons; (2) the role of spin, heavy quarks, and nuclei in unraveling fundamental phenomenological features of QCD; and (3) a new approach to understanding the scale and scheme dependence of perturbative QCD predictions.
  • The world experts in theory and experiment presented the most recent developments in the six topics; Light-Cone Field Theory, New Methods in Nonperturbative QCD, Phenomenology Confronting QCD, Effective Field Theory in Hadrons, High Temperatures and Density QCD and Critical Experiments Testing QCD.
  • The foundation of the path-integral derivation of anomalies is investigated. The combined use of zeta-function regularization and the background-field method clarifies the generality as well as limitations of the path-integral method and reveals the way to treat nonlinear systems. As an application, a detailed study of conformal anomalies in quantum chromodynamics is presented. By virtue of background gauge covariance the conformal Ward-Takahashi identities are cast into an equivalent background covariant form suited for the actual calculation of the anomaly.
  • The effective QCD charge extracted from {tau} decay is remarkably constant at small momenta, implying the near-conformal behavior of hadronic interactions at small momentum transfer. The correspondence of large-N{sub c} supergravity theory in higher-dimensional anti-de Sitter spaces with gauge theory in physical space-time also has interesting implications for hadron phenomenology in the conformal limit, such as constituent counting rules for hard exclusive processes. The utility of light-front quantization and lightfront Fock wavefunctions for analyzing such phenomena and representing the dynamics of QCD bound states is reviewed. I also discuss the novel effects of initial- and final-state interactions in hard QCDmore » inclusive processes, including Bjorken-scaling single-spin asymmetries and the leading-twist diffractive and shadowing contributions to deep inelastic lepton-proton scattering.« less
  • Separate abstracts were prepared for the four lectures included in the seminar.