Novel High Transverse Momentum Phenomena in Hadronic and Nuclear Collisions

Conference · Fri Apr 10 00:00:00 EDT 2009

OSTI ID:953010

Brodsky, Stanley J

I discuss a number of novel phenomenological features of QCD in high transverse momentum reactions. The presence of direct higher-twist processes, where a proton is produced directly in the hard subprocess, can explain the 'baryon anomaly' - the large proton-to-pion ratio seen at RHIC in high centrality heavy ion collisions. Direct hadronic processes can also account for the deviation from leading-twist PQCD scaling at fixed x{sub T} = 2 p{sub T}/{radical}s. I suggest that the 'ridge' --the same-side long-range rapidity correlation observed at RHIC in high centrality heavy ion collisions is due to the imprint of semihard DGLAP gluon radiation from initial-state partons which have transverse momenta biased toward the trigger. A model for early thermalization of the quark-gluon medium is also outlined. Rescattering 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, diffractive hard hadronic reactions, the breakdown of the Lam-Tung relation in Drell-Yan reactions, nuclear shadowing--all leading-twist dynamics not incorporated in the light-front wavefunctions of the target computed in isolation. Anti shadowing is shown to be quark flavor specific and thus different in charged and neutral deep inelastic lepton-nucleus scattering. I also discuss other aspects of quantum effects in heavy ion collisions, such as 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, and the important consequences of color-octet intrinsic heavy quark distributions in the proton for particle and Higgs production at high x{sub F}. I also discuss how the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories allows one to compute the analytic form of frame-independent light-front wavefunctions of mesons and baryons and to compute quark and gluon hadronization at the amplitude level. Finally, the BLM method for determining the renormalization scale in PQCD calculations is reviewed.

• Research Organization: Stanford Linear Accelerator Center (SLAC)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 953010
• Report Number(s): SLAC-PUB-13571; arXiv:0904.3037
• Conference Information: Presented at 4th International Workshop on High-pT physics at LHC 09, Prague, Czech Republic, 4-7 Feb 2009
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
74 ATOMIC AND MOLECULAR PHYSICS
AMPLITUDES
BARYONS
BREAKDOWN
DEEP INELASTIC SCATTERING
GLUONS
HEAVY IONS
MESONS
PARTICLE RAPIDITY
Phenomenology-HEP
HEPPH
HEPTH
PROJECTILES
PROTONS
QUANTUM CHROMODYNAMICS
QUARKS
RADIATIONS
RENORMALIZATION
RESCATTERING
SCATTERING
TARGETS
THERMALIZATION
TRANSVERSE MOMENTUM