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Pion double charge exchange above the {Delta}3/2,3/2 resonance

Thesis/Dissertation ·
OSTI ID:10103505
The first exclusive measurements of ({pi}{sup +}{pi}{sup {minus}}) reactions on several nuclei for incident pion energies from 300 to 550 MeV are reported. The measurements were made with the Large Acceptance Spectrometer at the P{sup 3} channel of the Clinton P. Anderson Meson Physics Facility. A description of the experimental setup is given which includes a discussion of modifications to the spectrometer and channel implemented specifically for these measurements. Forward angle excitation functions for transitions to the double isobaric analog state (DIAS) are found to be relatively flat for these energies. This energy dependence is reproduced by optical and Glauber calculations, but not by a six-quark bag prediction. The mass dependence of the DIAS was found to qualitatively agree with the predicted mass dependence from optical calculations. One angular distribution was measured for 5{degrees} {le} {Theta}{sub lab} {le} 35{degrees} for {sup 18}O({pi}{sup +}{pi}{sup {minus}}){sup 18}Ne. The DIAS cross section falls by more than one order of magnitude over this range, as predicted by both Glauber and optical model calculations. Data for f{sub 7/2}-shell nuclei were examined with a two-amplitude model based on seniority-zero shell model wavefunctions which features expressions for cross sections for DIAS transitions and transitions to nonanalog ground-states. The cross sections for T = 1 nuclei are found to be inconsistent with the predictions of the model. One excitation function for nonanalog transitions was measured and is relatively flat with energy. The continuum of nonanalog states near threshold was found to decrease with energy.
Research Organization:
Los Alamos National Lab., NM (United States)
Sponsoring Organization:
USDOE, Washington, DC (United States)
DOE Contract Number:
W-7405-ENG-36
OSTI ID:
10103505
Report Number(s):
LA--12209-T; ON: DE92003621
Country of Publication:
United States
Language:
English