CHING, CR (reprint author), CHINA CTR ADV SCI & TECHNOL,WORLD LAB,CTR THEORET PHYS,BEIJING,PEOPLES R CHINA.
The influence of nuclear Fermi motion on the conventional mechanism of pion double charge exchange (DCX) is examined. Concrete calculations of the 0-degrees excitation function over the energy region 0-300 MeV are performed for the double-isobaric-analog-state (DIAS) DCX transition on C-14. The calculated results coincide very well with the experimental data for energies above 100 MeV, but are about a factor of 2 smaller than the experimental data around 50 MeV. It indicates that the pure conventional mechanism seems incapable to explain fully the anomalous behavior of the low-energy DCX, and some new mechanisms are needed.