"Nuclear physics." . . "Nuclear reactions." . . "(Pions." . . "Pions)" . . . "The concept of 'Target Mass' and 'Effective Target Mass' is discussed. Evidence is presented which questions the validity of attempting to relate the 'Effective Target Mass' to the concept of a virtual pion surrounding the nucleon. Relations between the 4-momentum transfer, the quantity (E - P cos theta) of the recoil nucleon and the 'Effective Target Mass' are derived which show in conjunction with experimental data that the 'Effective Target Mass' of the order of a pion mass occurs accidentally. (Author)."@en . . . . . "'Target mass' and 'effective target mass'"@en . . . . . . . . "Mass energy relation." . . "ROCHESTER UNIV N Y." . . "Nuclear cross sections)" . . "(Nuclear cross sections." . "Recoil atoms." . . . . "Mass number." . . "Nucleons." . .