Nuovo Cim.A

The differential cross-sections for elastic scattering of π+ and π− mesons on4He have been measured at 68 and 154 MeV with a high-pressure helium streamer chamber. A phase-shift analysis (ACE method) has been carried out. The importance of the high partial waves is discussed.

Nuovo Cim.A

The cross-section for the$\pi ^ ++ ^4 He \to \pi ^ -+ 4p$ reaction has been measured with a high-pressure helium streamer chamber triggered by a scintillation counter hodoscope. Measurements were made for angles between 25° and 165°. Supposing the angular distribution of the secondary meson to be isotropic, we obtained the following total cross-section for the double charge exchange:$\sigma _{tot}= \left( {0.30 \pm 0.15} \right) \cdot 10^{ - 27} cm^2$. The obtained value turned out to be somewhat smaller than expected from calculations using the pair correlation model.

Nuovo Cim. A

The differential cross-sections for the elastic scattering of π+ and π− mesons on3He have been measured at 154 MeV with a high-pressure streamer chamber for angles between 30° and 160° (c.m.s.). The total elastic cross-sections are also presented.