Phy107Lect37

Phy107Lect37 - From Last Time Discussed the weak...

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Fri. Dec 10 Phy107 Lecture 37 From Last Time… • Discussed the weak interaction • All quarks and leptons have a ‘weak charge’ – They interact through the weak interaction • Weak interaction often swamped by electromagnetic or strong interaction. • Most clearly manifested in particle decays.
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Fri. Dec 10 Phy107 Lecture 37 Today • Unification of the electromagnetic and the weak force – the Standard Model • Where do particles get mass? – The Higgs mechanism and the Higgs boson(s) • Prospects for unifying all of particle physics – Grand Unified Theories
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Fri. Dec 10 Phy107 Lecture 37 Fundamental Matter Particles Three generations of leptons and quarks All feel the weak force. Charged leptons feel Quarks feel weak, EM, & strong
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Fri. Dec 10 Phy107 Lecture 37 Similar particles… • All six quarks can change flavor via the weak interaction. • Leptons can change flavor within a generation, and neutrinos between generations • View 12 fundamental matter particles as only two different types: different flavors are just diff. ‘orientations’.
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Fri. Dec 10 Phy107 Lecture 37 And several different interactions • Remember that interactions are due to exchange of bosons. • EM interaction - exchange photons • Weak interaction - exchange W + , W , Z o • Strong interaction - exchange gluons (8)
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Fri. Dec 10 Phy107 Lecture 37 Exchange Bosons (force carriers) EM Weak
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Fri. Dec 10 Phy107 Lecture 37 Electro-weak unification The standard model says that the weak interaction ( W + , W - , Z o exchange) are different pieces of the same electroweak interaction Neutral weak Electromagnetic • Zero charge • Mass=91 GeV/c 2 • Range ~ 10 -18 m • Zero charge • Mass=0 GeV/c 2 • Range ~ inf. Pos. weak Neg. weak • Pos. charge • Mass=80 GeV/c 2 • Range ~ 10 -18 m • Neg. charge • Mass=80 GeV/c 2 • Range ~ 10 -18 m W + W - ν e e
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Phy107 Lecture 37 Some similarities here These two both exchange neutral bosons Neither boson changes the lepton flavor (remains electron) Neutral weak Electromagnetic • Zero charge • Mass=91 GeV/c 2 • Range ~ 10 -18 m • Zero charge • Mass=0 GeV/c 2 • Range ~ inf. Pos. weak Neg. weak • Pos. charge • Mass=80 GeV/c 2 • Range ~ 10 -18 m • Neg. charge • Mass=80 GeV/c 2 • Range ~ 10 -18 m W + W - ν e e These two both exchange charged bosons. change the lepton flavor
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Phy107Lect37 - From Last Time Discussed the weak...

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