The chapter discusses the excitation function of the C12(p, p n)C11 reaction, emphasizing that the cross section is relatively insensitive to the energy of the incident proton within the studied energy range. This behavior is consistent with similar findings for reactions producing Na28, Na29, F18 from aluminum and Be2 from carbon. The probability of ejecting a small number of nucleons from a small nucleus remains constant over a wide range of bombarding energies, suggesting that the incident particle leaves behind a relatively small amount of energy. However, meson production increases significantly with energy, becoming a probable process. In heavy nuclei, this can lead to a shift in the maximum energy deposition spectrum and a decrease in the likelihood of reactions involving only a few particles. In contrast, in light nuclei, the reabsorption of mesons is less significant due to their greater escape probability, suggesting that the cross sections for similar reactions remain relatively unchanged. The chapter also delves into the concept of isotopic spin and isotopic gauge invariance, exploring the possibility of invariance under local isotopic spin rotations. This leads to the formulation of a principle of isotopic gauge invariance and the existence of a b field, which has a relationship to isotopic spin similar to the electromagnetic field to electric charge. The b field satisfies nonlinear differential equations, and its quanta are particles with spin unity, isotopic spin unity, and electric charges ±e or zero. The chapter discusses the field equations, quantization, and properties of the b quanta, including their electric charge and mass. The mass of the b quantum remains an open question, and its determination is crucial for understanding the consistency of the b field proposal with experimental data.The chapter discusses the excitation function of the C12(p, p n)C11 reaction, emphasizing that the cross section is relatively insensitive to the energy of the incident proton within the studied energy range. This behavior is consistent with similar findings for reactions producing Na28, Na29, F18 from aluminum and Be2 from carbon. The probability of ejecting a small number of nucleons from a small nucleus remains constant over a wide range of bombarding energies, suggesting that the incident particle leaves behind a relatively small amount of energy. However, meson production increases significantly with energy, becoming a probable process. In heavy nuclei, this can lead to a shift in the maximum energy deposition spectrum and a decrease in the likelihood of reactions involving only a few particles. In contrast, in light nuclei, the reabsorption of mesons is less significant due to their greater escape probability, suggesting that the cross sections for similar reactions remain relatively unchanged. The chapter also delves into the concept of isotopic spin and isotopic gauge invariance, exploring the possibility of invariance under local isotopic spin rotations. This leads to the formulation of a principle of isotopic gauge invariance and the existence of a b field, which has a relationship to isotopic spin similar to the electromagnetic field to electric charge. The b field satisfies nonlinear differential equations, and its quanta are particles with spin unity, isotopic spin unity, and electric charges ±e or zero. The chapter discusses the field equations, quantization, and properties of the b quanta, including their electric charge and mass. The mass of the b quantum remains an open question, and its determination is crucial for understanding the consistency of the b field proposal with experimental data.