Direct-photon production in heavy-ion collisions

Journal Article · Mon Mar 01 00:00:00 EST 1993 · Physical Review, D (Particles Fields); (United States)

DOI:https://doi.org/10.1103/PhysRevD.47.1906· OSTI ID:7014807

Petridis, A ^[1]; Lassila, K E ^[2]; Vary, J P ^[1]

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1. Department of Physics and Astronomy, Iowa State University, Ames, IA (United States) Ames Laboratory, Iowa State University, Ames, IA (United States)
2. Department of Physics and Astronomy, Iowa State University, IA (United States) Ames Laboratory,Iowa State University, Ames, IA (United States) Soltan Institute for Nuclear Studies, 00-681 Warsaw (Poland)

To study plasma photons in relativistc heavy-ion collisions one must account for direct photons from all possible sources. The aim of this work is the examination of the effect that initial-state parton distributions in nuclei, distorted to accommodate the European Muon Collaboration (EMC) effect, will have on the direct-photon spectrum produced relative to the basic QCD subprocesses in free nucleon-nucleon collisions. Since this parton distortion has been quite satisfactorily described by an expansion of the nuclear state in multiquark color-singlet (cluster) basis states, this quark cluster model'' should give useful predictions for the reflection of the EMC effect in the nucleus-nucleus direct photons. The presence of such clusters enhances the phase space available to direct photons. As a result, the direct-photon yield per nucleon shows significant dependence on the photon transverse momentum [ital p][sub [ital T]]. The ratio of the cross section per nucleon for zero photon longitudinal rapidity in collisions of two similar heavy nuclei to the cross section for collisions of two free protons exhibits deviations from unity, being less than one for small values of [ital p][sub [ital T]], and larger than one for large values of [ital p][sub [ital T]]. We investigate the sensitivity of this ratio on the mass number of the colliding projectiles, on the effective multiquark cluster probability, and on the nucleon or multiquark cluster gluon distributions for various values of the heavy-ion momentum per nucleon.

• DOE Contract Number: FG02-87ER40371; W-7405-ENG-82
• OSTI ID: 7014807
• Journal Information: Physical Review, D (Particles Fields); (United States), Vol. 47:5; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
HEAVY ION REACTIONS
PARTICLE PRODUCTION
PHOTONS
EMC EFFECT
GLUONS
PARTON MODEL
PHASE SPACE
QUANTUM CHROMODYNAMICS
RELATIVISTIC RANGE
BOSONS
CHARGED-PARTICLE REACTIONS
COMPOSITE MODELS
ELEMENTARY PARTICLES
ENERGY RANGE
FIELD THEORIES
MASSLESS PARTICLES
MATHEMATICAL MODELS
MATHEMATICAL SPACE
NUCLEAR REACTIONS
PARTICLE MODELS
POSTULATED PARTICLES
QUANTUM FIELD THEORY
SPACE
663450* - Heavy-Ion-Induced Reactions & Scattering- (1992-)
662230 - Quantum Chromodynamics- (1992-)