Pion-nucleus scatter and the Pauli principle
A density expansion of the pion self-energy for pions in nuclear matter is reexamined. It is shown that a single hole-line expansion of the self-energy (i) is equivalent to using a strongly quenched ..pi..N scattering amplitude in the medium, and (ii) results in an inconsistent treatment of the virtual pions necessarily present in a field-theoretic description of the problem. Exchange of intermediate pions gives rise to nucleon-nucleon, as well as pion-nucleon scattering diagrams that both contribute to the pion self-energy in an essential way. The nucleon-nucleon scattering proceeds, for instance, via a one-pion-exchange potential that is, however, highly nonstatic for energy transfers between nucleons close to the incident energy. Such interactions are singled out automatically for special treatment in a field-theory approach to the problem, and should not be introduced in an ad hoc manner as part of an empirical NN interaction in nuclear matter. We evaluate the coherent and charge exchange contributions to the pion-nucleus optical potential, proportional to the total density and the neutron-proton density difference, respectively. The Pauli principle is found to provide a small correction to the coherent part, both in the hole-line and density expansion formalisms. However, the charge exchange part of the potential is almost completely damped at low energies in the hole-line expansion, while the inclusion of backward-going graphs (random-phase-approximation-type correlations) restores it to its value based on free space ..pi..N charge exchange amplitudes (i.e., no net Pauli effect). (AIP)
- Research Organization:
- Physics Department, Brookhaven National Laboratory, Upton, New York 11973
- OSTI ID:
- 7329670
- Journal Information:
- Phys. Rev., C; (United States), Journal Name: Phys. Rev., C; (United States) Vol. 14:6; ISSN PRVCA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Pauli-blocking effects in low energy pion--nucleus scattering
Pauli blocking in the nuclear medium π N transition matrix
Related Subjects
653003* -- Nuclear Theory-- Nuclear Reactions & Scattering
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
AMPLITUDES
BASIC INTERACTIONS
BOSONS
CHARGE-EXCHANGE INTERACTIONS
CHARGED-PARTICLE REACTIONS
COUPLING CONSTANTS
EFFECTIVE RANGE THEORY
ELEMENTARY PARTICLES
ENERGY
HADRON REACTIONS
HADRON-HADRON INTERACTIONS
HADRONS
INTERACTIONS
MATTER
MESON REACTIONS
MESON-BARYON INTERACTIONS
MESON-NUCLEON INTERACTIONS
MESONS
NUCLEAR MATTER
NUCLEAR REACTIONS
OPTICAL MODELS
PARTICLE INTERACTIONS
PAULI PRINCIPLE
PERTURBATION THEORY
PION REACTIONS
PION-NUCLEON INTERACTIONS
PIONS
PSEUDOSCALAR MESONS
SCATTERING AMPLITUDES
SELF-ENERGY
STRONG INTERACTIONS