π++12Celastic scattering between 18 and 44 MeV

Pion-nucleus elastic scattering, double-charge-exchange reactions, and subthreshold resonances

“…In this paper we presented an explanation for the energy dependence in the excitation function in scattering of positive pions from 12 C at pion energies in the 30 -35 MeV region which were observed in Ref. [1]. It is shown that these oscillations can be explained by formation of the quasi-stationary pionic atom states in the vicinity of the threshold of the DCX reaction channel.…”

“…The narrowness of this region may explain why other experimental groups (a detailed comparison of existing experimental data is given in Ref. [1]) did not see these oscillations. Fortunately, in Ref.…”

“…Fortunately, in Ref. [1] the data sets at different pion's energies included the pion's energy at 35.4 MeV.…”

“…The results of calculations of the excitation function with and without taking into account the sub-threshold resonance effect at all scattering angles measured in Ref. [1] are presented in Figure 2. These calculations were performed with γ = 0.1 (Γ e tot ≈ 0.04 MeV) that was found to provide the best description of the data at 83 • .…”

“…A systematic measurement of energy dependence of the elastic scattering of positive pions from 12 C presented in Ref. [1] showed oscillations in the excitation function at energies around 35 MeV. The differential cross sections were measured at six scattering angles (37 • , 65 • , 83 • , 103 • , 118 • , 142 • ) in the energy range of 18-44 MeV with an increment in the incident energy of 2 MeV.…”