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Standard Model of Particle Physics. Forces: Theories of Mechanisms: Action at a Distance Action through fields Action through exchange of particles or “force carriers” Four Forces: Strong, Weak , E&M, Gravitation “electroweak” (E&M and weak are linked)
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Standard Model of Particle Physics Forces: Theories of Mechanisms: Action at a Distance Action through fields Action through exchange of particles or “force carriers” Four Forces: Strong, Weak , E&M, Gravitation “electroweak” (E&M and weak are linked) GUT’s: Grand Unified Field Theories (attempt to link the strong force to the others.) TOE’s: Theories of Everything: attempt to link Gravity to the others; “Quantum Gravity”
Two types of Particles • Fermions: • have ½ integer spin • Compose all matter • Have antiparticles • Bosons • Have integer spin • If elementary: act as force carriers for interacting fermions • Otherwise, can be composed of fermions • Each is its own antiparticle.
Fundamental Fermions • Quarks • Compose heavier particles (the Hadrons) • Have fractional charge: (+ ⅔ e, -⅓ e) • Antiparticles have charge: (- ⅔ e, + ⅓ e) • 6 types called “flavors” (plus their antiparticles) • Up, down, strange, charmed, bottom, top • u, d, s, c, b, t ; antiparticles have bars on top. • (+ ⅔ e): u, c, t ; (-⅓ e): d, s, b • Size: r ~ 10-17m • Interact via the strong force • Leptons • Lighter particles, integer charge (ex: electrons, neutrinos)
The Hadrons • Composed of quarks • Quarks are never observed free. • Baryons • Composed of 3-quark combinations resulting in integer charge • Proton: uud (charge = +e) • Neutron: udd (charge =0) • Baryon number is conserved in particle reactions • Antiparticles have negative baryon number. • Mesons • Composed of quark-antiquark pairs ex: pion: π+: u(dbar) • unstable
Instruments of Particle Physics Particle Accelerators (ex: Cyclotron): Accelerate particles to very high kinetic energies.
Accelerators (cont’d) • Synchrotrons • Increase B-field as particles speed up • X-ray lithography: microelectronics, micromachining. • High Energy Spectroscopy : • To dislodge inner electrons from atoms • Get a map of energy levels as higher electrons cascade down. • Large Hadron Collider – • Collide protons at near the speed o fthe light to emulate big bang conditions.
Particle Detectors • To analyze particles created from collisions of other particles. • Composed of lead glass or crystals • Particles travel faster than speed of light in the material, giving off “Cerenkov Light” • Analysis of light allows determination of mass and charge of particles.