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Title: Novel QCD Phenomenology

Abstract

I review a number of topics where conventional wisdom in hadron physics has been challenged. For example, hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation. Such 'direct' processes can explain the deviations from perturbative QCD predictions in measurements of inclusive hadron cross sections at fixed x{sub T} = 2p{sub T}/{radical}s, as well as the 'baryon anomaly', the anomalously large proton-to-pion ratio seen in high centrality heavy ion collisions. Initial-state and final-state interactions of the struck quark, the soft-gluon rescattering associated with its Wilson line, lead to Bjorken-scaling single-spin asymmetries, diffractive deep inelastic scattering, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as nuclear shadowing and antishadowing. The Gribov-Glauber theory predicts that antishadowing of nuclear structure functions is not universal, but instead depends on the flavor quantum numbers of each quark and antiquark, thus explaining the anomalous nuclear dependence measured in deep-inelastic neutrino scattering. Since shadowing and antishadowing arise from the physics of leading-twist diffractive deep inelastic scattering, one cannot attribute such phenomena to the structure of the nucleus itself. It is thus important to distinguish 'static' structure functions, the probability distributions computed from the squaremore » of the target light-front wavefunctions, versus 'dynamical' structure functions which include the effects of the final-state rescattering of the struck quark. The importance of the J = 0 photon-quark QCD contact interaction in deeply virtual Compton scattering is also emphasized. The scheme-independent BLM method for setting the renormalization scale is discussed. Eliminating the renormalization scale ambiguity greatly improves the precision of QCD predictions and increases the sensitivity of searches for new physics at the LHC. Other novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates.« less

Authors:
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1022580
Report Number(s):
SLAC-PUB-14265
arXiv:1010.1503; TRN: US1104294
DOE Contract Number:  
AC02-76SF00515
Resource Type:
Conference
Resource Relation:
Conference: Invited talk at Gribov-80 Memorial Workshop on Quantum Chromodynamics and Beyond, Miramare, Trieste, Italy, 26-28 May 2010
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 74 ATOMIC AND MOLECULAR PHYSICS; BREAKDOWN; COMPTON EFFECT; CONDENSATES; CONFINEMENT; CROSS SECTIONS; DEEP INELASTIC SCATTERING; FINAL-STATE INTERACTIONS; GLUONS; HADRONS; HEAVY IONS; NEUTRINOS; NUCLEAR STRUCTURE; PHYSICS; QUANTUM CHROMODYNAMICS; QUANTUM NUMBERS; QUARKS; RENORMALIZATION; RESCATTERING; SCATTERING; STRUCTURE FUNCTIONS; TRANSVERSE MOMENTUM; Phenomenology-HEP, Theory-HEP,GRQC, HEPPH, HEPTH

Citation Formats

Brodsky, Stanley J, and /SLAC /Southern Denmark U., CP3-Origins. Novel QCD Phenomenology. United States: N. p., 2011. Web.
Brodsky, Stanley J, & /SLAC /Southern Denmark U., CP3-Origins. Novel QCD Phenomenology. United States.
Brodsky, Stanley J, and /SLAC /Southern Denmark U., CP3-Origins. 2011. "Novel QCD Phenomenology". United States. https://www.osti.gov/servlets/purl/1022580.
@article{osti_1022580,
title = {Novel QCD Phenomenology},
author = {Brodsky, Stanley J and /SLAC /Southern Denmark U., CP3-Origins},
abstractNote = {I review a number of topics where conventional wisdom in hadron physics has been challenged. For example, hadrons can be produced at large transverse momentum directly within a hard higher-twist QCD subprocess, rather than from jet fragmentation. Such 'direct' processes can explain the deviations from perturbative QCD predictions in measurements of inclusive hadron cross sections at fixed x{sub T} = 2p{sub T}/{radical}s, as well as the 'baryon anomaly', the anomalously large proton-to-pion ratio seen in high centrality heavy ion collisions. Initial-state and final-state interactions of the struck quark, the soft-gluon rescattering associated with its Wilson line, lead to Bjorken-scaling single-spin asymmetries, diffractive deep inelastic scattering, the breakdown of the Lam-Tung relation in Drell-Yan reactions, as well as nuclear shadowing and antishadowing. The Gribov-Glauber theory predicts that antishadowing of nuclear structure functions is not universal, but instead depends on the flavor quantum numbers of each quark and antiquark, thus explaining the anomalous nuclear dependence measured in deep-inelastic neutrino scattering. Since shadowing and antishadowing arise from the physics of leading-twist diffractive deep inelastic scattering, one cannot attribute such phenomena to the structure of the nucleus itself. It is thus important to distinguish 'static' structure functions, the probability distributions computed from the square of the target light-front wavefunctions, versus 'dynamical' structure functions which include the effects of the final-state rescattering of the struck quark. The importance of the J = 0 photon-quark QCD contact interaction in deeply virtual Compton scattering is also emphasized. The scheme-independent BLM method for setting the renormalization scale is discussed. Eliminating the renormalization scale ambiguity greatly improves the precision of QCD predictions and increases the sensitivity of searches for new physics at the LHC. Other novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates.},
doi = {},
url = {https://www.osti.gov/biblio/1022580}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Aug 12 00:00:00 EDT 2011},
month = {Fri Aug 12 00:00:00 EDT 2011}
}

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