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

Technical Report · Tue May 01 04:00:00 EDT 1990

DOI:https://doi.org/10.2172/6901545· OSTI ID:6901545

Yoo, Sung Hoon

Angular distributions for the {sup 12}C({pi}{sup {plus minus}}, {pi}{sup {plus minus}}{prime} p) and {sup 208}Pb({pi}{sup {plus minus}}, {pi}{sup {plus minus}}{prime} p or n) reactions near the giant resonance region have been measured at T{sub {pi}} = 180 MeV, and found different between {pi}{sup +} and {pi}{sup {minus}} data. This observation is interpreted as evidence for different excitation mechanisms dominating the {pi}{sup {minus}}-nucleus and {pi}{sup +}-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 {plus minus}}, {pi}{sup {plus minus}}{prime} N) data for both targets, the dominance of direct process for ({pi}{sup +}, {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 +}, {pi}{sup +}{prime} n). In the ({pi}{sup +}, {pi}{sup +}{prime} p) reaction proton-proton 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) the preferentially excited neutron-neutron hole doorway states couple to resonance states and decay with spreading width. This interpretation led us 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. 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: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE/ER; RAWF
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 6901545
• Report Number(s): LA-11767-T; ON: DE90011508
• Country of Publication: United States
• Language: English

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR DISTRIBUTION
BORN APPROXIMATION
CARBON 12
CARBON ISOTOPES
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DATA ACQUISITION SYSTEMS
DETECTION
DISTRIBUTION
DWBA
EVEN-EVEN NUCLEI
FUNCTIONS
GIANT RESONANCE
HADRON REACTIONS
HEAVY NUCLEI
INELASTIC SCATTERING
ISOTOPES
LEAD 208
LEAD ISOTOPES
LIGHT NUCLEI
MESON REACTIONS
NUCLEAR REACTIONS
NUCLEAR STRUCTURE
NUCLEI
PION REACTIONS
RESONANCE
SCATTERING
STABLE ISOTOPES
WAVE FUNCTIONS