Three‐nucleon force effects in 3N hadronic and photonic reactions

Results on three‐nucleon (3N) elastic scattering and breakup below the pion production threshold are discussed with emphasis on the need for a three‐nucleon force (3NF). The large discrepancies found between a theory based on numerical solutions of 3N Faddeev equations with modern NN potentials only and data point to the need for 3NF's. Successes and failures of the present 3NF models, mostly of a 2π‐exchange nature, to describe high precision 3N data are discussed. Effects due to relativity both in elastic nucleon‐deuteron (Nd) scattering and breakup reaction are presented and consequences for a 3NF study pointed out. As an application of 3N bound and scattering states, results for photodisintegration of 3N bound states are shown.