The total cross section of the ${}^4\mathrm{He}({\pi }^{+},{\pi }^{-})$ reaction was measured for ${\pi }^{+}$ kinetic energies ranging from 70 to 130 MeV using the CHAOS spectrometer at TRIUMF and a liquid ${}^4\mathrm{He}$ target. Around $T_{\pi }=90\mathrm{}\mathrm{MeV},$ total cross sections exceed conventional model predictions by a factor of 3, whereas at $T_{\pi }=70\mathrm{}\mathrm{MeV}$ and for $T_{\pi }>130\mathrm{}\mathrm{MeV}$ the data are consistent with these calculations. An attempt is made to understand this behavior by assuming the production of the hypothetical $d^{\prime }$ dibaryon.

• Received 21 April 1998

DOI:https://doi.org/10.1103/PhysRevC.58.1576