(. pi. sup +- ,. pi. sup +- prime N) reactions on sup 12 C and sup 208 Pb near the giant resonance region

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:5845548

Yoo, S H

Angular distributions for the {sup 12}C({pi}{sup {+-}}, {pi}{sup {+-}{prime}} p) and {sup 208} Pb({pi}{sup {+-}}, {pi}{sup {+-}{prime}} p or n) reactions near the giant resonance region have been measured at T{sub {pi}} {equals} 180 MeV, and found different between {pi}{sup {plus}} and {pi}{sup {minus}} data. This observation is interpreted as evidence for different excitation mechanisms dominating the {pi}{sup {minus}}-nucleus and {pi}{sup {plus}}-nucleus interactions in the giant resonance region of these targets. A comparison with the single nucleon knock-out distorted-wave impulse approximation calculations shows, even though these calculations underestimate ({pi}{sup {+-}}, {pi}{sup {+-}{prime}} N) data for both targets, the dominance of direct process (due to quasi-free scattering) for ({pi}{sup {plus}},{pi}{sup {plus}{prime}} p) or ({pi}{sup {minus}}, {pi}{sup {minus}{prime}} n) in contrast to ({pi} {sup {minus}}, {pi}{sup {minus}{prime}} p) or ({pi}{sup {plus}}, {pi}{sup {plus}{prime}} n). In the ({pi}{sup {plus}}, {pi}{sup {plus}{prime}} p) (or ({pi}{sup {minus}}, {pi}{sup {minus}{prime}} n)) reaction proton proton hole states (neutron-neutron hole states) are excited directly and appear to have a large probability for direct decay with escape width, whereas in ({pi}{sup {minus}}, {pi}{sup {minus}{prime}}p) (or ({pi}{sup {plus}},{pi}{sup {plus}{prime}} n)) the preferentially excited neutron-neutron hole doorway states couple to resonance states and decay with spreading width. This interpretation led the author to suggest that the ratio of cross-sections for inelastic scattering to the giant resonance region should be written in terms of an incoherent sum of cross-sections to neutron and proton doorway states. In a heavy nucleus such as {sup 208}Pb, neutron and proton doorway states contribute incoherently because the different decay processes do not populate the same final states of the residual nucleus.

• Research Organization: Texas Univ., Austin, TX (USA)
• OSTI ID: 5845548
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
CARBON 12 TARGET
PION MINUS REACTIONS
PION PLUS REACTIONS
LEAD 208 TARGET
QUASI-ELASTIC SCATTERING
ANGULAR DISTRIBUTION
COMPARATIVE EVALUATIONS
DWBA
GIANT RESONANCE
INELASTIC SCATTERING
KNOCK-OUT REACTIONS
MEV RANGE 100-1000
NEUTRONS
NUCLEAR REACTION KINETICS
PIONS MINUS
PIONS PLUS
PROTONS
BARYONS
BORN APPROXIMATION
BOSONS
CHARGED-PARTICLE REACTIONS
DIRECT REACTIONS
DISTRIBUTION
ELEMENTARY PARTICLES
ENERGY RANGE
FERMIONS
HADRON REACTIONS
HADRONS
KINETICS
MESON REACTIONS
MESONS
MEV RANGE
NUCLEAR REACTIONS
NUCLEONS
PION REACTIONS
PIONS
PSEUDOSCALAR MESONS
QUASI-FREE REACTIONS
REACTION KINETICS
RESONANCE
SCATTERING
TARGETS
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