EVIDENCE FOR THE QUASIFREE CHARACTER OF THE (PI-(+/-),PI-N) REACTIONS ON C-12, MG-24, AND CA-40

Cross sections for (π±,πN) reactions near the Δ(1232) resonance on C12, Mg24, and Ca40 leading to mirror levels in C11/B11, Mg23/Na23, and Ca39/K39, respectively, were measured by observing their γ decays. σnσp for the first 12- levels in C11/B11 is 1.4±0.2 for π- and 11.8±0.2 for π+. For Mg23/Na23 and Ca39/K39, the ratios are generally not as closely reciprocal as for C11 and the previously reported O15/N15 32- level case. The most strongly excited mirror level pairs are those with large (p,d) and (He3,d) spectroscopic factors. The results are interpreted as evidence for the quasifree character of these (π,πN) reactions. NUCLEAR REACTIONS C, Mg, Ca(π±, πN), E=200 MeV; detected γ's, Ge(Li); measured 90°σ for residual mirror levels; deduced σ ratios. © 1979 The American Physical Society.