Final answer:
The deep inelastic scattering experiments at SLAC revealed that protons have a quark structure through the inelastic scattering of high-energy electrons, providing key evidence for quarks with fractional charges and spin 1/2.
Step-by-step explanation:
The deep inelastic scattering experiment is a significant event in physics that led to the discovery of the quark structure of the proton. In experiments at SLAC (Stanford Linear Accelerator Center), high-energy electrons were fired at protons. Some of these electrons were deflected at very large angles, indicative of small, dense scattering centers within the proton. Analyses of these collisions suggested that matter contained smaller constituents than protons and neutrons, which were identified as quarks with specific properties, such as spin 1/2 and fractional electric charges of +2/3e or -1/3e. These findings provided strong evidence for the existence of quarks, fundamentally altering our understanding of subatomic particles and contributing to the standard model of particle physics. In contrast to elastic collisions, where the kinetic energy is conserved and the colliding objects do not undergo internal changes, the SLAC experiments involved inelastic collisions where the kinetic energy was not conserved in the collision between the electrons and the protons. This was important because it allowed for the transfer of energy to the internal structure of the proton, revealing the presence of quarks. This discovery was analogous to the outcomes of the Rutherford gold foil experiment, where alpha particles were scattered by the nuclei of gold atoms, indicating that atoms had a dense nucleus and leading to the planetary model of the atom.