Particle Physics: Status and Perspectives Part 1: Particles Manfred Jeitler

2 Overview (1)  what are elementary particles?  the first particles to be discovered  historical overview  a few formulas  relativistic kinematics  quantum mechanics and the Dirac equation  common units in elementary particle physics  the Standard Model  detectors  accelerators

3 Overview (2)  completing the Standard Model  the second generation (charm and J/ψ)  the third generation (beauty (bottom) and Υ (“upsilon”), top)  gauge bosons of electroweak interactions: the W and Z bosons  testing at the Precision Frontier: the magnetic moment of the leptons  the Higgs boson  fundamental symmetries and their violation  parity violation  CP-violation  T-violation

4 Overview (3)  neutrinos and neutrino oscillations  particle physics and cosmology, open questions  the Energy Frontier and the Precision Frontier  Supersymmetry  dark matter  gravitational waves  slides and formulas at

5 Literature  A few useful books are:  Donald Perkins, Introduction to High Energy Physics  Otto Nachtmann, Elementary Particle Physics  You will find many other good books in your library  On recent experiments, much useful information can be found on the internet (Wikipedia, home pages of the various experiments etc.)

What are (elementary) particles? 6

the electron e-e- Thomson

8 J.J. Thomson’s “plum-pudding model” of the atom... the atoms of the elements consist of a number of negatively electrified corpuscles enclosed in a sphere of uniform positive electrification,...

the proton e-e Rutherford p

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the photon  Planck Einstein Compton e-e- p

the neutron e-e  1914 n p 1932 Chadwick

the positron (anti-matter) e-e  1914 e+e+ p 1932 n Anderson Dirac

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the muon e-e  1914 µ p 1932 n 1937 Hess Anderson, Neddermeyer e+e+ Who ordered this ?

muon lifetime  muon lifetime ~ 2.2 μs  speed of muons: almost speed of light  speed of light = ?  path travelled by muons = ? 18

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20 relativistic kinematics  elementary particles travel mostly at speeds close to speed of light  because their masses are small compared to typical energies  (almost) always use relativistic kinematics  in particle physics, “special relativity” is sufficient most of the time  remember a few basic formulae !

a bit of maths  Special Relativity  Quantum Mechanics  Dirac Equation 21

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23 relativistic kinematics 1 v 1/γ

e-e- 1V the electron-volt (eV)  eV: 3 K cosmic background radiation (~ 0.25 meV)  eV: room temperature (~ 30 meV)  eV: ionisation energy for light atoms (13.6 eV in hydrogen)  10 3 eV (keV): X-rays in heavy atoms  10 6 eV (MeV): mass of electron m e = 511 keV/c 2  10 9 eV (GeV): mass of proton (~1GeV/c 2 )  ~ 100 GeV/c 2 : mass of W, Z  ~ 200 GeV/c 2 : mass of top  eV (TeV): range of present-day man-made accelerators  eV: highest energies seen for cosmic particles  eV (10 19 GeV/c 2 ): ~ Planck mass units: energy and mass

25 units: speed and distance  velocity: speed of light  ~ 3 * 10 8 m/s  ~ 30 cm/ns  approximately, all speeds are equal to the speed of light in high-energy particle physics !  all particles are “relativistic”  distance: fm (femtometer)  1 fm = m  sometimes also called “Fermi”

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27 relations and constants  waves  λ × ν = c  ω = 2π ν  quantum mechanics  h Planck constant (“Planck’sches Wirkungsquantum”)  h = h / 2π  hν = hω = E  numerical survival kit  c = h = 1  as long as you need no “usual” units; and then, use:  c ~ 3 × 10 8 m/s speed of light  hc ~ 200 MeV × fm  ??? protons / kg (~ GeV / kg) Avogadro’s number  e = ??? As (coulomb)  1 eV ~ ??? K Boltzmann’s constant  1 eV ~ ??? J  1 Tesla = ??? gauss

28 relations and constants  waves  λ × ν = c  ω = 2π ν  quantum mechanics  h Planck constant (“Planck’sches Wirkungsquantum”)  h = h / 2π  hν = hω = E  numerical survival kit  c = h = 1  as long as you need no “usual” units; and then, use:  c ~ 3 × 10 8 m/s speed of light  hc ~ 200 MeV × fm  ~ 6 × protons / kg (~ GeV / kg) Avogadro’s number  e ~ 1.6 × 10 −19 As (coulomb)  1 eV ~ 10 4 K Boltzmann’s constant  1 eV ~ J  1 Tesla = gauss

29 “natural” units  c = h = 1  c ~ length/time speed of light  hc ~ energy × length  length ~ time ~ 1/energy  1 GeV −1 ~ 10 −16 m (=0.1 fm) ~ 10 −24 s  V = -G m 1 m 2 / rgravitational attraction  G ~ m -2  G = M Planck -2 particles with this mass would at ~proton-size distance have gravitational energy of ~proton mass  M Planck ~ GeV  L Planck = 1/M Planck ~ m  t Planck = 1/M Planck ~ s

30 gravitation is weak!  V grav = - G m 1 m 2 / rgravitational potential = - M Planck -2 m 1 m 2 / r ~ m 1 m 2 / r  V elec = (1 / (4πε 0 ) ) q 1 e q 2 e / r electrostatic potential = (e 2 / (4πε 0 hc) ) q 1 q 2 / r = α q 1 q 2 / r α = fine structure constant ~ (1/137) q 1 q 2 / r ~ q 1 q 2 / r  V grav / V elec ~ / =

the pion e-e  1914  p 1932 n 1937 µ 1947 Powell Yukawa e+e+

EXPI, Aug Force carriers Interaction between particles due to exchange of other (“virtual”) particles L.J. Curtis gauge bosons

the neutrino e-e  1914 p 1932 n 1937 µ 1947  e+e+ Pauli Reines

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„strange“ particles e-e  1914 K K p 1932 n 1937 µ 1947  e+e+ Rochester, Butler,    

Too many particles!

37 life time (s) n  cc KLKL D KcKc KSKS 00   B  J   1s  2s  3s  4s   D* cc 00  mass (GeV/c 2 ) the particle zoo 1s 1 ms 1 µs s s s n  KLKL D KcKc KSKS 00   B  J   1s  2s 3s3s  4s   D* cc 00  E=1eV e - W ±, Z o p 1 ns

„I have heard it said that the finder of a new elementary particle used to be rewarded by a Nobel Prize, but that now such a discovery ought to be punished by a $10,000 fine.“ e-e  1914 K p 1932 n 1937 µ 1947  e+e   In his Nobel prize speech in 1955, Willis Lamb expressed nicely the general attitude at the time: Lamb

The “particle zoo” of the subatomic world Is there something analogous to the Periodic Table of the elements?

? ? ? ? ? ? ? Is there something missing?

The periodic table today

42 Teilchen Wechselwirkungen stark schwach e Ladung 0 +2/3 -1/3 gravitation ? weak W, Z electromagnetic  strong g e     d u s c b t +1/ d u d u u d u d Proton Neutron q q q q q „Leptonen“ „Quarks“

43 Anti-Teilchen Wechselwirkungen stark schwach e Ladung /3 +1/3 gravitation ? weak W, Z electromagnetic  strong g e     d u s c b t +1 Pion (  ) d u

44  ++ u u u  d d d u s  u u s  c d DD s u  b b 

45 fermions (spin ½) charge 0 +2/3 -1/3 d u u d u d leptonsquarks the Standard Model +1 0 proton neutron baryons interactions strong weak gravitation ? weak W, Z electromagnetic  strong g force carriers = bosons (spin 1) e e     uct dsb

46 d u s c b t e e     anti -particles interactions strong weak e charge /3 + 1/3 gravitation ? weak W, Z electromagnetic  strong g e     d u s c b t leptonsquarks force carriers = bosons (spin 1)

47 d u s c b t e e     anti -particles interactions strong weak e charge /3 + 1/3 gravitation ? weak W, Z electromagnetic  strong g e     d u s c b t leptonsquarks force carriers = bosons (spin 1)

48 the 4 fundamental interactions Gravitation Strong Interaction Electromagnetism Weak Interaction

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50 lifetime and width  due to the uncertainty principle, the lifetime of a state (= unstable particle) and the accuracy, with which its mass (= rest energy) is reproduced at subsequent measurements, are correlated: Δt × ΔE ~ h  lifetime can be measured directly for fairly long-lived states ( > s)  width can be measured directly for short-lived states (becomes immeasurably small for long-lived states)  both properties can always be converted into each other: τ = h / Γ Γ = h / τ  remember: hc ~ 200 MeV × fm c = 3 ~ fm/s  h ~ 2/3  MeV × s

cross section 51

cross section 52

53 cross section  defined via scattering probability W = n × σ  n... number of scatterers in beam  σ... cross section of individual scatterer  naive picture: each scatterer has a certain “area” and is completely opaque  absorption cross section  can also be used for elastic scattering...  into certain solid angle dΩ: dσ/dΩ ... or particle transformation  differential cross section for a certain reaction  unit: “barn”: (10 fm) 2 = 100 fm 2 = m 2 = cm 2

cross section 54

cross sections at LHC 55

56 fundamental interactions interactionStrongelectro- magnetic Weakgravity gauge boson gluonphotonW, Zgraviton mass00~ 100 GeV0 range 1 fm  fm  source“color charge” electric charge “weak charge” mass coupling~ 1α ~ 1/ typical σfm fm fm 2 - typical lifetime (s)

57 Feynman diagrams

58 electron scattering (Bhabha scattering)

59 Feynman diagrams for electromagnetic interactions

60 Feynman diagrams for Weak interactions

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63 experimental setup for measuring deep-inelastic electron-proton scattering (from Robert Hofstadter’s Nobel prize lecture, 1961)

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66 color charge coloranticolor REDCYAN BLUEYELLOW GREENMAGENTA Apart from their electric charge, quarks also have “color charge”. The particles which convey this interaction and keep the quarks together are called gluons.

67 Free quarks have never been observed, they always appear in bound states (quark confinement). 2 types of bound states are observed: 3 quarks of three different colors: baryons 2 quarks of a color and its anticolor: mesons baryons q q q q q d u mesons q q

68 Feynman diagrams for Strong interactions

69 3-jet event (Aleph experiment, LEP Collider, CERN, Geneva, Switzerland)

70  ++ u u u  u d d u s  c d DD s u  b b  d u u d u d protonneutron mesons baryons... nucleus He nucleus (  -particle) atom matter

71 Robert Hofstadter (Nobel prize lecture, 1961)

72 e e µ µ decay     e e    26 ns  2200 ns scattering e-e- e+e+ e+e+ K K p p e-e- e+e+ e+e+ What do we observe? decays & scattering K K  

73 fermions (spin ½) charge 0 +2/3 -1/3 leptonsquarks the Standard Model interactions strong weak gravitation ? weak W, Z electromagnetic  strong g e e     uct dsb Astro Accelerator