Probing three-nucleon-force effects through knockout reactions

Understanding of the roles of three-nucleon forces (3NFs) in nuclear few- and many-body systems is one of the fundamental subjects in nuclear physics. In this talk, we propose to use proton knockout reactions (p,2p), which can be regarded as a two-proton quasielastic scattering, as a new probe into 3NF effects on reaction observables. In a many-body system, 3NF effects can be represented by the density-dependence of nucleon-nucleon effective interaction. Proton knockout reactions from a deeply bound orbit should be suitable for probing 3NF effects since such reactions occur mainly in the internal region of the target nucleus in which the density is high. We clarify the roles of 3NF for knockout reactions based on the distorted-wave impulse approximation with a nucleon-nucleon g-matrix interaction including the 3NF effects. The 3NF effects significantly change the peak height of the triple differential cross section of (p,2p) reactions.