Positron Annihilation. Before: After: Electron-Positron Pair Production. (For photons of energy > 1.022 MeV). Bosons:
Quantum Mechanics: Note 9
Elementary Particles Elementary particles are the simplest building blocks of matter. They are all part of something in physics called THE STANDARD MODEL. All elementary particles are either fermions or bosons. Fermions are the particles that make up all of the regular matter that we are used to, while bosons explain the four fundamental forces of nature using something called exchange particles. Fermions Fermions come in two types: quarks and leptons. Quarks
Hadron
Mesons (Quark-Antiquark Pair)
Pion
Kaon
Baryons (3 Quark Combonations)
Eta
Protons
Neutrons
Lambda
Sigma
Omega
Quarks make up these particles. Every meson has two quarks with some examples are listed above. Every baryon has three quarks with examples listed above such as protons and neutrons. Any particle made up of quarks is called a hadron. Hadrons are the particles that are commonly used at places like CERN in Geneva and Fermilab in Chicago. There are six different types of quarks and antiquarks. Different combinations of these quarks make different particles: Name Charge Name Charge Quarks Antiquarks Some examples of quark combinations: Protons: Neutrons: Pions:
There are six types of leptons (three pairs). The bottom partner leptons in each pair (positron, muon-, tau-) are also referred to as neutrinos. Leptons are continuously being created and destroyed (some more than others) using two methods: Positron Annihilation Electron-Positron Pair Production (For photons of energy > 1.022 MeV) Before: After:
Bosons: Exchange Particles We know about the four fundamental forces, but how do they work? As matter interacts with each other, they exchange tiny, tiny particles between their respective elementary particles (i.e. the fermions in a magnet exchange boson particles with the fermions in a piece of metal, which causes an attraction force. The more particles exchanged, the stronger the force.) Force Particle Exchanged Range Electromagnetism Photon ∞ -17 Weak Nuclear Force Weak Boson 10 m Strong Nuclear Force Gluon 10-15 m Gravity Graviton* ∞ *Note: The graviton has not yet been confirmed The Higgs Boson Peter Higgs predicted the existence of another boson in the 1960’s – now called the Higgs boson and confirmed at CERN in 2012. The Higgs boson is an exchange particle between all massive objects and something exterior to those objects called the Higgs field. The more Higgs bosons that are exchanged, the more massive an object is. Problems With The Standard Model This model of particle physics is incomplete. We expect that there should be WIMPS (dark matter particles), but the standard model makes no prediction of them.
