The Standard Model is a remarkably successful synthesis of much that we know about electromagnetic, weak and strong nuclear forces. It also classifies all known subatomic particles. As new experimental data emerges, the Standard Model continues to evolve and its view of the subatomic domain expands. In the 1970s, experiments confirmed the existence, as predicted, of quarks. In the decades that followed, discoveries of the top quark, tau neutrino, and Higgs boson further established the validity of the Standard Model.
There remain unexplained phenomena. The Standard Model does not include a complete theory of gravitation as depicted in Albert Einstein’s relativistic scheme of large-scale interactions in time and space. Nor does it cover dark energy and its role in the observed accelerating expansion of the universe. There is no theory of a dark matter particle as recent astronomical observations would seem to require. Also lacking is coverage of neutrino oscillations.
Nevertheless, the standard model succeeds in bringing together theoretical and experimental knowledge of the quantum reality. It is the only frame of reference we have for evaluating new highly counterintuitive theories regarding hypothetical particles, extra dimensions, string theory and supersymmetry as these speculations strive to shed light into today’s rapidly proliferating knowledge base.
In the Standard Model, all elementary particles have a property known as spin. The two categories of elementary particles are fermions (named after Enrico Fermi) and bosons (named after Salyendra Nath Bose). There are 12 elementary particles that are fermions, and they have a half-integer spin.
Bosons are the force carriers. The value of their spin is one. Fermions conform to the Pauli exclusion principle, which states that two fermions cannot occupy the same position in time and space, i.e. be at the same energy level. In this respect, they resemble billiard balls. Each fermion has a corresponding antiparticle. Bosons, in contrast, do not conform to the Pauli exclusion principle, so their spatial density is not limited.
The Higgs boson, predicted by the Standard Model and recently confirmed experimentally, is a huge elementary particle. It has no spin. A strange fact is that in particle collider experiments, the less massive particles are easier to “see”. That is why the Higgs boson eluded investigators until the present decade.
The Higgs Boson (this really happens) generates the mass of each lepton – electron, muon and tau – and quark. In our next article, we’ll look at that very small particle.
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