Elementary particle the proton should be uniform and the electron should scatter elastically. Low-energy electrons do scatter in this way, but, above a particular energy, the protons deflect some electrons through large angles. The recoiling electron has much less energy and a jet of particles is emitted. This inelastic scattering suggests that the charge in the proton is not uniform but split among smaller charged particles: quarks. In the Standard Model, vector (spin-1) bosons (gluons, photons, and the W and Z bosons) mediate forces, whereas the Higgs boson (spin-0) is responsible for the intrinsic mass of particles. Bosons differ from fermions in
Particle zoo as the Standard Model, and includes quarks, bosons and leptons. Particle zoo In particle physics, the term particle zoo is used colloquially to describe a relatively extensive list of the then known "elementary particles" by comparison to the variety of species in a zoo. In the history of particle physics, the situation was particularly confusing in the late 1960s. Before the discovery of quarks, hundreds of strongly interacting particles (hadrons) were known, and believed to be distinct elementary particles in their own right. It was later discovered that they were not elementary particles, but rather composites of the quarks. The