l17 - Announcements Exam 2 is on Tuesday 3/30 Review...

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ISP209s10 Lecture 17 -1- Announcements • Exam 2 is on Tuesday 3/30 • Review session on Thursday 3/25 • You are allowed to bring 5 pages of notes (front and back) to the exam • Today: The Standard Model – 4 forces of Nature – Fundamental particles of Nature – Feynman diagrams
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ISP209s10 Lecture 17 -2- From large to small Atoms Atomic Nucleus A proton (uud) Made of nuclei and electrons. Size: 10 -9 m Made of neutrons and proton. Size 10 -14 m Made of quarks: Size 10 -15 m A neutron has ddu
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ISP209s10 Lecture 17 -3- The big picture • Forces come about because of some properties of particles (charge, mass, weak charge, color charge). Recall, particles <=> quanta of matter fields. • The force is transmitted by the exchange of “force carrier” particles (photon, graviton, vector boson, gluon) that are the quanta of some force field (Electromagnetic, gravitational, Weak, Strong)
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ISP209s10 Lecture 17 -4- There are two more forces in nature – Strong Force The Strong force – A force that exists between quarks, which have a property called color charge. – The carrier of the force is the gluon (the gluon also has color charge) – No isolated quarks are found in nature – The force between protons-proton, protons-neutrons, and neutrons-neutrons is the result of the exchange of pairs of quarks called mesons. – The Strong force is responsible for binding atomic nuclei.
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ISP209s10 Lecture 17 -5- The Weak Force Weak force • A force between electrons, neutrinos and protons (or neutrons), due to a property of matter called weak charge. • The carrier of the force are called weak vector bosons W+ or W-, Z. The + or – tells us the electric charge of the boson. • This force allows a neutron to change into a proton and is responsible for most radioactive decays.
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ISP209s10 Lecture 17 -6- 2 4 6 8 10 Distance [am] 1 2 3 4 5 6 7 WeakPotential Weak Potential The weak force falls off faster than 1/r 2 . Remember, the slope gives the magnitude of the field (force). distance quark quark Electric potential shape - 1/r Weak potential
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ISP209s10 Lecture 17 -7- A summary of the 4 forces of nature infinite Graviton (?) 6x10 -39 Gravity 10 -18 Only 0.001 width of proton Vector Bosons W +, W - , Z 0 10 -6 Weak infinite photon 1/137 Electromagnetic 10 -15 size of a proton Gluon, g, between quarks Mesons-protons/neutrons 1 Strong Range (m) Carrier Strength Force
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l17 - Announcements Exam 2 is on Tuesday 3/30 Review...

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