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Particle Physics

Particle Physics. Professor Kay Kinoshita University of Cincinnati. Particle Physics (also called High Energy Physics) at UC. Faculty Theory Experiment Philip Argyres Randy Johnson Bernard Goodman* Kay Kinoshita Alex Kagan Brian Meadows Joe Scanio Alan Schwartz

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Particle Physics

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  1. Particle Physics Professor Kay Kinoshita University of Cincinnati

  2. Particle Physics (also called High Energy Physics) at UC • Faculty • TheoryExperiment • Philip Argyres Randy Johnson • Bernard Goodman* Kay Kinoshita • Alex Kagan Brian Meadows • Joe Scanio Alan Schwartz • Peter Suranyi* Mike Sokoloff • Rohana Wijewardhana • Louis Witten* • *emeritus

  3. Reference materials • History and description of Standard Model: • The Particle Adventure • CP Violation http://www.particleadventure.org/ http://www.physics.uc.edu/~kayk/cpviol/CP.html

  4. what is particle physics? • • matter and energy: • the study of elementary particles and forces between them “elementary” = not made up of other, “smaller,” particles • • matter • “everyday” matter is made of atoms • each atom consists of a nucleus & electrons • each nucleus is made up of protons & neutrons • each proton/neutron contains even smaller particles, called quarks • quarks and electrons are believed to be elementary • • forces (interactions) • in classical physics • hold matter together • push matter apart

  5. what is a force? • Classical forces • gravitational • exists between two objects with mass • electromagnetic • exists between two objects with electric charge • • Matter experiences a force if it carries a property (“charge”) that couples to that force

  6. what is a force? • • In addition to gravitation and electromagnetism, particles are known to be influenced by two other forces, strong and weak, which cannot be described within classical physics – need relativistic quantum mechanics: • strong • exists between particles with “strong charge”, or “color” • weak • exists between particles with “weak charge” • .

  7. what is a force? • In relativistic quantum mechanics • • interactions are depicted as exchanges of particles (field quanta) associated with force • • matter can be turned into energy and vice versa: E=mc2 • • anti particle is equivalent to particle traveling backward in time • • elementary particles may turn into other elementary particles X scattering Y X annihilation anti-X X’ Y Z X decay

  8. what is a force? • strong force • • holds protons and neutrons together in nuclei • • 3 types of “charge” = 3 colors • combination of 3 is neutral, “singlet” • => 3 quarks in proton, neutron • • field quantum: gluon (8 types) • • strength: weak at very short distances, • strong at (~1) > nuclear dimensions (few x 10–15 m) • => quarks can only exist in bound “color singlet” states • .

  9. what is a force? • weak force • • responsible for beta decay • • the only force that allows particles to change into others • •symmetry-violating (P, CP) couplings • • 3 field quanta: Z0, W+,W– • • strength: too weak to bind matter (~10–5) • .

  10. what is a force? • electromagnetic force • • binds electrons to nuclei • • field quantum: photon • • strength ~ 10–2 • .

  11. what is a force? • gravitational force • • apples, solar systems, galaxies, ... • • field quantum: graviton (not yet seen) • • strength: ~ 10–38 • .

  12. what is the Standard Model? • • explains everything (so far) in terms of • 12 elementary particles: 6 quarks, 6 leptons • Strong, Electromagnetic, and Weak forces • (gravitation not yet included effectively in the theory) electric charge –e 0 +2e/3 –e/3 e– e 3 generations –  -  leptons (color = 0) interesting patterns... up down charm strange top bottom quarks

  13. what is different about the Weak Interaction? seen suppressed not seen Z0 "neutral current" • • universality of weak charge in quarks is not apparent for interactions involving W± • ... unlike interactions involving Z0 • • observe “CP violation” <-> complex “weak charge” e– e –  -  leptons (universal) up down charm strange top bottom quarks (all different)

  14. what is different about the Weak Interaction? Cabibbo-Kobayashi-Maskawa (CKM) matrix  unitary d' s’ = b' d s b • • universality of weak charge seen by modifying picture: • weak force sees {d,s,b} as mixed quantum mechanical states • => weak charge is universal, but in a “rotated” perspective complex preserves metric “ orthogonality up d’own charm s’trange top b’ottom

  15. Kobayashi & Maskawa (1973) •  proposed 3rd generation of particles • could explain CP violation in K (& predict for B) due to complex nature of 3-generation matrix (vs. 2) B-Factory experiments [SLAC (Stanford), KEK(Japan)] (1999-2009) • CP asymmetry observed in diverse processes in B decay -> many measurements, (over)constrain CKM, confirm unitarity

  16. Is there more? ... yes (out of time) Is there more to be understood? Undoubtedly! • gravity is not included in the Standard Model • astrophysical evidence for “dark matter”, “dark energy” (???) • history tells us that patterns hint at new laws • new accelerators – LHC, super B-factory – the next microscopes electric charge –e 0 +2e/3 –e/3 e– e 3 generations –  -  leptons (color = 0) WHY? 3 generations 2 leptons/2 quarks pattern of charges up down charm strange top bottom quarks

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