Pion absorption and the eta lifetime in the nucleus

A brief exposition is made of many body theory for pion nucleus interaction which provides a unified description of all inclusive pion nuclear reactions around the resonance region. Pion absorption is a very important channel and it gets contribution from two and three nucleon mechanisms. A new experimental check for three nucleon pion absorption is suggested and the analogies with the decay channels of an η meson in the nucleus are drawn, with the tentative conclusion that the η width in the nucleus should be considerably larger than previously estimated, hence making the observation of eta-nuclei far more difficult