20 Particle and Nuclear physics

20 Particle and Nuclear physics - Plan for Today Exam 2...

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Physics 13 Lecture 20 Prof. H. Gallagher Plan for Today Exam 2 Nuclear Physics 1. Radioactivity 2. Nuclear decays Fundamental Forces Don’t forget that the schedule was modified from the original version handed out on the first day. Final version is on Blackboard.
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Physics 13 Lecture 20 Prof. H. Gallagher Exam 2 Mean score was 81.3% Standard deviation is 15.4% Several scores >100% If you did not do as well as you hoped: You can earn back up to half of the points you lost by doing well on this material on the final. Extra credit projects (3% to your total grade). I would like to finalize the list of students doing EC projects by next Tues. Let me know if you are interested! Nov. 28, 2006 2
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Physics 13 Lecture 20 Prof. H. Gallagher 3 Beyond the atom First particle physicist: Democritus - earth, air, fire water! Mendeleev was able to demonstrate a regularity in the known elements, which was later explained in terms of atomic substructure (protons, neutrons, and electrons). Neutron discovered by James Chadwick ( 1935 ). H. Yukawa ( 1949 ) suggested that the force holding the nucleus together is a short range force because it is due to the exchange of a massive particle whose lifetime is determined by the uncertainty principle. Predicted the pion (mass 139 MeV), physicists immediately went looking for it and found lots of other things besides. For instance the muon (105 MeV). Exactly like the electron, just 200 times heavier! http://particleadventure.org/particleadventure/frameless/scale.html
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Physics 13 Lecture 20 Prof. H. Gallagher 4 Standard Model Overview Two different kinds of matter, which comes in 3 generations: quarks: feel the strong force, fermions leptons: do not feel the strong force, fermions And “Force Carrier” particles, “gauge bosons”, associated with the 4 forces of nature. •Strong (gluon) •Weak (W and Z bosons) •Electromagnetic (photon) •Gravitational (gravitino ?) In addition there is anti-matter as predicted by the Dirac equation! -1 -1/3 +2/3 0 charge
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Physics 13 Lecture 20 Prof. H. Gallagher 5 Strong Force Relative strength: 1 Range: 1 fm Felt by quarks (and particles made up of quarks) Carried by gluons. Charge:
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20 Particle and Nuclear physics - Plan for Today Exam 2...

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