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The must fundamental constituents of matter Physics 100 Chapt 26
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Anaximenes Anaximenes ~600BC All types of matter are formed from different combinations of: Earth Air Fire Water
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Closer to home Earth Wind Fire Water Elements
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Anaximenes idea Good point: Economical –All of matter reduced to 4 easy-to-remember components Bad point: Wrong –Alchemists (including Isaac Newton) tried for centuries to changing one chemical element into another with no success
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Enter Mendeleev All matter is comprised of different combinations of (now 92) different chemical elements Good point Correct; successfully predicted the existence of Scandium, Gallium & Germanium Bad point Uneconomical; 92 basic constituens
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Rutherford All elements are constructed from 3 basic particles: electrons neutrons protons Feel the strong force & are heavy hadrons Doesn’t feel the strong force & is light lepton
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The “elementary particles” circa 1935 Categoryparticlesymbolchargemc 2 strongelectricweak Leptons electron e-e- 0.511 MeV noyes neutrino 0~0no yes Hadrons proton p+1 938.3 MeV yes neutron n0 939.6 MeV yes Light photon 00noyesno Economy is restored Forces felt
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These “good” times didn’t last long
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Paul Adrien Maurice Dirac 1902 - 1984 Combined relativity & Quantum Mechanics
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p = mV x p x = mV x E = 1/2 mv 2 p y = mV y y Pre relativity p x can be + or - E is always +
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p = mV x p x = mV x E = mc 2 2 2 () ± p y = mV y y p x can be + or - E also can be + or - Post relativity:
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QM waves: =h/p f=E/h Pre relativity: p = m 0 v (v =p/m 0 ) E = 1/2 m 0 v 2 =p 2 / 2 m 0 = h/p can be + or f=p 2 / 2 m 0 h always +
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QM waves: =h/p f=E/h after relativity: p = m 0 v (v =p/m 0 ) E 2 = (mc 2 ) 2 E= ± mc 2 = h/p can be + or f= can be + or mc 2 h
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Negative wavelength : wave in backward direction. Negative frequency : wave backward in time????
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What does it mean to move backwards in time?
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backward time motion t B when viewed forward in time: LR : C : P
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When antimatter comes in contact with matter, what happens?
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-+- + - +
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Anti-hydrogen p + Anti-hydrogen atoms are made routinely at the CERN laboratory in Switzerland. It is found to have the same size and allowed energy levels as ordinary hydrogen
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Anti-Carbon + + + + + + antielectrons antineutrons antiprotons Although it would be impossibly difficult to make anti-atoms more complex than anti- hydrogen, it is in principle possible
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CP Violation: Asymmetry matter anti- matter Big Bang matter- antimatter symmetric all matter no antimatter
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Our research Where did all the anti-people go???
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Include anti-particles in our list Categoryparticlesymbolchargemc 2 symbolcharge Leptons electron e-e- 0.511 MeV positron e+e+ +1 neutrino 0~0 anti- neutrino 0 Hadrons proton p+1 938.3 MeV anti- proton p neutron n0 939.6 MeV anti- neutron n0 Light photon 00 0 anti-particle particle
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Quantum Electro-Dynamics (QED) Combined Relativity, Quantum Mechanics and Photons into one single theory Richard FeynmanJulian Schwinger Shinichiro Tomonaga
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QED explains action-at-a-distance
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QED is a fabulously accurate theory QED theory measure Strength of electrons magnetic field:
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Ideas of QED strong nuclear force Hideki Yukawa Short range (10 -15 m) of the strong nuclear force: predicts existence of a “ ” particle M c 2 140 MeV 1935
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Look for in cosmic rays
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“Spark chamber” tracks
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+ and – particle discovered in cosmic rays m + c 2 = m - c 2 = 106 MeV Near expectations for Yukawa’s Experiments show that the + & - do not feel the Strong Nuclear Force and, therefore, cannot be Yukawa’s the + & - are additional leptons (i.e. like the e + & e - but with larger mass)
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Yukawa’s finally discovered in 1947 In fact there are 3 of them: + M + c 2 = 139.6 MeV 0 M 0 c 2 = 135.0 MeV - M - c 2 = 139.6 MeV Anti- particles Photographic emulsion
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“Atom smashers”
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Inside the accelerator tunnel
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e + e - collider
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Belle Detector
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Electronic detectors
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Fermilab (near Chicago) 2 km detector
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Inside a Fermilab Tunnel
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Biggest of all is in Europe ~5 miles
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Detectors
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Neutrino interacts in a Bubble Chamber
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Leptons (circa 2005) anti-particle particle namesymbolchargemc 2 namesymbolcharge electron ee 0.511 MeV positron ee +1 electron neutrino e 0~0 anti-elec neutrino e 0 muon +1 105.7 MeV anti- muon +1 muon- neutrino 0~0 anti-mu neutrino 0 tau 1876 MeV anti- tau +1 tau- neutrino 0~0 anti-tau neutrino 0
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1950’s & 1960’s, Many other particles are discovered p - M=1116MeV
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K 0 “meson” K 0 - M=498 MeV
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Two classes of hadrons Baryons (p, n, , …..) ultimate decay products include a proton Mesons ( , K, …) ultimate decay products e’s, ’s & ’s Both baryons & mesons feel the Strong Nuclear Force
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Lots of baryons have been discovered
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& even more mesons
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The elementary particle chart revisited Economy is lost!! 6 leptons: e e ; ; (+ 6 anti-leptons) Categoryparticlesymbol Leptons electron e-e- neutrino Hadrons proton p neutron n 1935 NOW hundreds of hadrons + anti-hadrons
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Elementary Particle Zoo Lepton House Electrons, Muons, Taus, & lots of neutrinos Hadron Savannah 100’s of Baryons, Latest new Mesons +anti particles galore & lots of photons Special today: live pions being exhanged proton neutron
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