The must fundamental constituents of matter Physics 100 Chapt 26

Anaximenes Anaximenes ~600BC All types of matter are formed from different combinations of: Earth Air Fire Water

Closer to home Earth Wind Fire Water Elements

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

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

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

The “elementary particles” circa 1935 Categoryparticlesymbolchargemc 2 strongelectricweak Leptons electron e-e MeV noyes neutrino 0~0no yes Hadrons proton p MeV yes neutron n MeV yes Light photon  00noyesno Economy is restored Forces felt

These “good” times didn’t last long

Paul Adrien Maurice Dirac Combined relativity & Quantum Mechanics

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 +

p = mV x p x = mV x E = mc () ± p y = mV y y p x can be + or - E also can be + or - Post relativity:

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 +

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

Negative wavelength : wave in backward direction. Negative frequency : wave backward in time????

What does it mean to move backwards in time?

backward time motion          t B when viewed forward in time:  LR : C : P

When antimatter comes in contact with matter, what happens?

   

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

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

CP Violation: Asymmetry matter anti- matter Big Bang matter- antimatter symmetric all matter no antimatter

Our research Where did all the anti-people go???

Include anti-particles in our list Categoryparticlesymbolchargemc 2 symbolcharge Leptons electron e-e MeV positron e+e+ +1 neutrino 0~0 anti- neutrino 0 Hadrons proton p MeV anti- proton p neutron n MeV anti- neutron n0 Light photon  00  0 anti-particle particle

Quantum Electro-Dynamics (QED) Combined Relativity, Quantum Mechanics and Photons into one single theory Richard FeynmanJulian Schwinger Shinichiro Tomonaga

QED explains action-at-a-distance

QED is a fabulously accurate theory QED theory measure Strength of electrons magnetic field:

Ideas of QED  strong nuclear force Hideki Yukawa  Short range ( m) of the strong nuclear force: predicts existence of a “  ” particle  M  c 2  140 MeV 1935

Look for  in cosmic rays

“Spark chamber” tracks

 + 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)

Yukawa’s  finally discovered in 1947 In fact there are 3 of them:  +  M  + c 2 = MeV  0  M  0 c 2 = MeV  -  M  - c 2 = MeV Anti- particles Photographic emulsion

“Atom smashers”

Inside the accelerator tunnel

e + e - collider

Belle Detector

Electronic detectors

Fermilab (near Chicago) 2 km detector

Inside a Fermilab Tunnel

Biggest of all is in Europe ~5 miles

Detectors

Neutrino interacts in a Bubble Chamber

Leptons (circa 2005) anti-particle particle namesymbolchargemc 2 namesymbolcharge electron ee MeV positron ee +1 electron neutrino e 0~0 anti-elec neutrino e 0 muon  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

1950’s & 1960’s, Many other particles are discovered   p  - M=1116MeV

K 0 “meson”      K 0     - M=498 MeV

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

Lots of baryons have been discovered

& even more mesons

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

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