Particle Physics "three quarks for Muster Mark" -James Joyce (Finnegan’s Wake) Contents: Particle Accelerators Quantum Electrodynamics and Feynman diagrams The Yukawa Particle Particles and Antiparticles Conservation Laws Types of Particles Strange Things and Quark Theory

Particle Accelerators TOC Basic concept - Vq = 1 / 2 mv 2 Provide energy for nuclear reactions Create particles from energy Proton Source Vacuum Beam Steering (RevereWare) Experiments +150,000 V

Particle Accelerators TOC SLAC - electron accelerator Potential switches 50 GeV - mass?

Particle Accelerators TOC Cyclotrons - In a magnetic field to curve path Potential switches Mass dilates as v->c Synchrotrons - Fermilab(1.0 km), CERN (8.5 km)

8.5 km in diameter

Quantum Electrodynamics TOC Coulomb’s law - Force fields Richard Feynman - EM forces are mediated by photons: Richard Feynman Feynman Diagram Virtual photons:  E  t > h / 2  (Exist for so short a time - never detected)

The Yukawa Particle TOC Photons mediate the EM force Yukawa proposes a particle to mediate strong nuclear force Hideki Yukawa He names it the meson - (between electron and proton)  E  t =  E( d / c ) = h / 2   E = hc / 2  d = 130 MeV

The Yukawa Particle TOC Hideki Yukawa Muon discovered in cosmic radiation m = 106 MeV - doesn’t interact The pi meson (pion) is discovered in 1947 in cosmic rays (3 charge states):  MeV/c 2  o MeV/c 2  MeV/c 2 p + p --> p + p +  o p + p --> p + n +  + (conservation of charge)

The Four Forces of Nature TOC Type Strong Nuclear Electromagnetic Weak Nuclear Gravitational Relative Strength Field Particle Gluons (mesons) Photon W + and Z o Graviton?

Particles and Antiparticles TOC NameParticleAntiparticle Electrone - e + p Protonpp Pion  +  - Some particles have no antiparticle + and - are electron charges When particle meets antiparticle - annihilation (rest mass + E k turns to energy or other particles)

Selected list (there are hundreds of hadrons) Self as antiparticle + and - are electron charges….

Conservation Laws - Baryon Number TOC Conservation of charge Conservation of mass/energy Conservation of nucleon.... In general, baryon number is conserved:

Conservation Laws - Baryon Number TOC In general, baryon number is conserved: This reaction can never happen: p + n -> p + p + p (Antiparticles have B = -1) Baryon numbers: 

Conservation Laws - Baryon Number TOC Heavy baryons decay to lighter ones Proton is lightest - must be stable

Whiteboards: Conservation of Baryon Number 11 | 2 | 3 | 4234 TOC

W 0 What is the total Baryon number of p + n + n +  = 0

What is the total Baryon number of  + +  + +  o +  = -1 W

yes Can this reaction occur? p + p --->  - +  = W

no Can this reaction occur? p + n --->  o +   W

no Can this reaction occur?  o + n --->  o +  + B: = C: != W

Conservation Laws - Lepton Number TOC Lepton number is conserved too L e - Electron/electron neutrino L  - Muon/muon neutrino L  - Tau/Tau neutrino Remember - anti particles have negative lepton numbers Neutrinos are believed to have mass

Conservation Laws - Lepton Number TOC Co Ni +  - + e 13 7 N 13 6 C +  + + e Beta Decay: Emission of an electron neutrino allowed L e to be conserved: L e L  L  Electrone-+100 Neutrino (e) e +100 Muon  Neutrino (  )  0+10 Tau  Neutrino (  )  00+1

Whiteboards: Conservation of Lepton Number 11 | 2 | 3 | 4 | TOC

W dog biscuit Does this decay occur?  - ---> e - + e Charge is conserved L e : 0 = L  : 1  L  is not conserved L e L  L  Electrone-+100 Neutrino (e) e +100 Muon  Neutrino (  )  0+10 Tau  Neutrino (  )  00+1

yo mama Does this decay occur?  - ---> e - + e +  Charge is conserved L e : 0 = L  : 1 = Yes it occurs W L e L  L  Electrone-+100 Neutrino (e) e +100 Muon  Neutrino (  )  0+10 Tau  Neutrino (  )  00+1

the red Does this decay occur?  - ---> e + e +  Charge is Not conserved L e : 0 = L  : 1 = Does not occur W L e L  L  Electrone-+100 Neutrino (e) e +100 Muon  Neutrino (  )  0+10 Tau  Neutrino (  )  00+1

 What is the missing decay product?  - --->  - +  + ??? W L e L  L  Electrone-+100 Neutrino (e) e +100 Muon  Neutrino (  )  0+10 Tau  Neutrino (  )  00+1 Q: -1= ? EL#: 0 = ? ML#: 0= ? TL#: 1 = ?

e+ What is the missing decay product?  + ---> ?? +  + e Q: +1=? EL#: 0 = ? ML#: -1= ? TL#: 0 =? W L e L  L  Electrone-+100 Neutrino (e) e +100 Muon  Neutrino (  )  0+10 Tau  Neutrino (  )  00+1

 What is the missing decay product?  + --->  + + ?? +  W L e L  L  Electrone-+100 Neutrino (e) e +100 Muon  Neutrino (  )  0+10 Tau  Neutrino (  )  00+1 Q: +1=+1 +? +0 EL#: 0 = 0 + ? +0 ML#: 0= -1 + ? +0 TL#: -1 =0 + ? +-1

-- What is the missing particle? ?? ---> e- + e +  W L e L  L  Electrone-+100 Neutrino (e) e +100 Muon  Neutrino (  )  0+10 Tau  Neutrino (  )  00+1 Q: ?= EL#: ? = ML#: ?= TL#: ? =

Types of Particles TOC Gauge Bosons - carry the electro-weak force Leptons - interact via weak and EM (charged) force Hadrons - interact via strong nuclear force Mesons - B = 0 Baryons - B = 1, (-1)…

Quark Theory TOC 1960s - Only 4 Leptons, but Hundreds of Hadrons Leptons seemed elementary/small (< m) Not all Hadrons could be elementary Murray Gell-Mann suggests that Hadrons are made from quarks.quarks "three quarks for Muster Mark" -James Joyce (Finnegan’s Wake)

Quark Theory TOC Murray Gell-Mann suggests that Hadrons are made from quarks.quarks

Quark Theory TOC Proton: +1 charge, B = 1 Neutron: 0 charge, B = 1 Pion + : +1 charge, B = 0 Pion-: -1 charge, B = 0 Kaon-: -1 charge, B = 0 Try making other Hadrons yourself

Truly Fundamental particles TOC Generally accepted fundamental particles Three generations Top quark = 200 GeV/c 2