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Elementary Particles

​         As we go through school, we learn that the objects around us are composed of matter, which is composed of electrons, protons, and neutrons. Although correct, this is not the complete story, for these particles, except for electrons, are actually composed of smaller, indivisible particles called quarks. ​ Quarks are subatomic particles that all have a spin of ½, binding together using the strong force to form more well-known particles like the neutron and proton, similar to how these particles cluster together to form atomic nuclei. They form hadrons using the strong nuclear force, hadrons being groups of composite particles made of multiple quarks that include protons and neutrons. This is similar to molecules and compounds that are composed of atoms bound together by electromagnetic force. There are 6 different types of quarks: up, charm, top, down, strange, and bottom. The first 3 have a ⅔ charge while the latter 3 all have a -⅓ charge. Quarks are also able to switch between different types, such as a down quark becoming an up quark. ​ Two up quarks combine with a down quark via the strong nuclear force to form the proton, a hadron. The up quark is the lightest quark, followed by the down quark. The strange quark, the third lightest, is a component of various obscure, short-lived particles that are not involved in ordinary matter.  The charm quark is the 3rd heaviest quark, initially discovered in 1974. The 2nd heaviest quark is the bottom quark, found in obscure hadrons. The top quark is the largest quark and elementary particle and was discovered in 1977. ​ The electron is the most well-known elementary particle, and it is part of the lepton group – elementary particles with ½ spin and integer electric charges that do not interact with the strong nuclear force. Leptons can have a +1, -1, or 0 charge. The charged leptons are considered muons or electron-like, and the neutral leptons are known as neutrinos. Neutrinos rarely interact with other particles and are thus rarely observed. Leptons include the electron, muon, tau, electron neutrino, muon neutrino, and tau neutrino. ​ Electrons help atoms stay together, and electron transfer and gradients are responsible for our everyday electromagnetic interactions, such as current flowing through a wire and magnets sticking together. The electron is the lightest non-neutrino lepton. It has a charge of -1, like the muon. The muon has more mass than an electron but has a lower mass than the tau particle. This higher mass corresponds with a slower acceleration, which proves to be useful for imaging objects, such as x-rays, due to slower energy dissipation. The tau also has a -1 charge and is the heaviest lepton. It decays into other particles due to the weak force. It can be thought of as a massive electron. The electron neutrino, discovered at UC Irvine in 1956, has no charge and very low mass. All neutrinos can pass easily through most mass and only interact with gravity and the weak nuclear force. They also have near 0 mass and 0 charge. Little information is known about the muon and tau neutrinos. ​ Bosons are characterized by integer spin and carrying force for lack of a better word. There can be infinite bosons within the same quantum state. Unlike the other particle groups, the quarks and leptons, which fall under the fermion banner, have integer spin, not fractional spin. Gauge or vector bosons comprise all bosons besides the Higgs boson. These bosons include photons, Z and W bosons, and gluons. Respectively, these bosons carry the electromagnetic force, weak nuclear force, and the strong nuclear force. Interestingly, there has been no discovered gravity boson yet, but the graviton is hypothesized to exist. It is thought to have no charge, a spin of 2, and no mass. ​ Gluons have a spin of 1 and bind quarks together to form the hadrons of protons and neutrons using the strong nuclear force. They can also interact with other gluons using this nuclear force. The Z and W bosons comprise the weak bosons and share a spin of 1. The W boson is charged with ±1 whereas the Z boson has no charge. The W boson can trigger nuclear fusion and convert particles into others such as protons into neutrons. Photons carry the electromagnetic force with a spin of 1. They are massless, but retain energy through momentum within the general case of Einstein’s mass-energy equivalence equation: E2 = p2c2 + m2c4. They have no charge, and they were the famous example of wave-particle duality discovered in the double-slit experiment. They have 0 mass due to their lack of Higgs Field interactions, and photons are also their own antiparticles. ​ The Higgs boson has a spin of 0, and it is produced from high-energy particle collisions in the Higgs Field. It gives other elementary particles their mass, and it can be thought of as proof of the Higgs field. 

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