Medium effects on binary collisions with the {Delta} resonance

Journal Article · Sun Sep 01 04:00:00 EDT 1996 · Physical Review, C

DOI:https://doi.org/10.1103/PhysRevC.54.1350· OSTI ID:383346

Lee, T H ^[1]

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1. Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843 (United States)

To facilitate the relativistic heavy-ion calculations based on transport equations, the binary collisions involving a {Delta} resonance in either the entrance channel or the exit channel are investigated within a Hamiltonian formulation of {pi}{ital NN} interactions. An averaging procedure is developed to define a quasiparticle {Delta}{asterisk} and to express the experimentally measured {ital NN}{r_arrow}{pi}{ital NN} cross section in terms of an effective {ital NN}{r_arrow}{ital N}{Delta}{asterisk} cross section. In contrast to previous works, the main feature of the present approach is that the mass and the momentum of the produced {Delta}{asterisk}{close_quote}s are calculated dynamically from the bare {Delta}{leftrightarrow}{pi}{ital N} vertex interaction of the model Hamiltonian and are constrained by the unitarity condition. The procedure is then extended to define the effective cross sections for the experimentally inaccessible {ital N}{Delta}{asterisk}{r_arrow}{ital NN} and {ital N}{Delta}{asterisk}{r_arrow}{ital N}{Delta}{asterisk} reactions. The predicted cross sections are significantly different from what are commonly assumed in relativistic heavy-ion calculations. The {Delta} potential in nuclear matter has been calculated by using a Bruckner-Hartree-Fock approximation. By including the mean-field effects on the {Delta} propagation, the effective cross sections of the {ital NN}{r_arrow}{ital N}{Delta}{asterisk}, {ital N}{Delta}{asterisk}{r_arrow}{ital NN} and {ital N}{Delta}{asterisk}{r_arrow}{ital N}{Delta}{asterisk} reactions in nuclear matter are predicted. It is demonstrated that the density dependence is most dramatic in the energy region close to the pion production threshold. {copyright} {ital 1996 The American Physical Society.}

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 383346
• Journal Information: Physical Review, C, Journal Name: Physical Review, C Journal Issue: 3 Vol. 54; ISSN PRVCAN; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CROSS SECTIONS
DELTA BARYONS
HAMILTONIANS
HARTREE-FOCK METHOD
HEAVY ION REACTIONS
NUCLEAR MATTER
PARTICLE PRODUCTION
PION-NUCLEON INTERACTIONS
PIONS
QUASI PARTICLES
RELATIVISTIC RANGE
TRANSPORT THEORY
UNITARITY