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Unformatted text preview: PHY3063 R. D. Field Department of Physics quark_1.doc University of Florida The Simple Structure of our Universe Elementary Particle: Indivisible piece of matter without internal structure and without detectable size or shape . . Four Forces: Gravity ( Solar Systems, Galaxies, Curved Space-Time , Black Holes ) Electromagnetism ( Atoms & Molecules, Chemical Reactions ) Weak ( Neutron Decay, Beta Radioactivity ) Strong ( Atomic Nuclei, Fission & Fusion ) Two Classes of Elementary Particles: Leptons: Do not interact with the strong force (but may interact with weak, EM and gravity). Quarks: Do interact with the strong force (may also interact with weak, EM and gravity). Quarks and Leptons have very different properties: 1. Weak and EM forces much weaker that strong force. 2. Quarks have fractional electric charge. 3. Quarks are found only as constituents of composite particles called hadrons ( baryons have B not 0, mesons have B = 0 ) . Leptons exist as free particles. Gauge Particles are the carriers (or mediators) of the forces: Electromagnetism Photon (massless) Weak Weak Vector Bosons W + , W- , Z (massive) Gravity Graviton Strong 8 Gluons (massless) Mass and chage located inside sphere of radius zero! Baryon Number PHY3063 R. D. Field Department of Physics quark_2.doc University of Florida Labeling the Particles Quantum Numbers Elementary particles and hadrons are labeled by their quantum numbers . These labels characterize the properties of the particles. Symbol Name Additive M Mass J Spin Angular Momentum C Charge Conjugation P Parity G G-Parity B Baryon Number Yes Q em Electric Charge Q = Y/2 + Iz Q = Q weak + Q U1 Yes Q U1 U1 Charge Yes Q weak Weak Charge Yes Q color Strong Charge Y Hypercharge Y = B + S + C h + B o + T o Yes S Strangness Yes C h Charmness Yes B o Bottomness Yes T o Topness Yes I Isospin Yes I z 3 rd component of Isospin Yes L e Electron Lepton Number Yes L Muon Lepton Number Yes L Tau Lepton Number Yes L Overall Lepton Number L = L e...
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