1. APPEAL, 2 July 2011 Introduction to Particle Physics Dr Alan Barr University of Oxford

3. The structure of matter… CELLS Twenty per mm DNA Five hundred thousand per mm Nucleus Five hundred billion per mm Quarks More than one million billion per mm Extra magnification? x 2 thousand x 25 thousand x 1 million Electron microscope Particle Accelerators 2 fm < 1 am 50 μm 2 nm Microscope

4. Key Equation De Broglie wavelength Planck Constant Momentum See small? Large momentum

5. What the world is made of Electron, e d quark Photon, γ Gluon, g Not to scale! Commonplace particles u quark  Constituents of everyday stuff

6. Discovery of the nucleus Happy 100 th birthday to the nucleus 1911 Earnest Rutherford Scattering of alpha particles from gold foil

7. Nucleus at centre of atom Gluons are ripples in the nuclear force field The size of the nucleus is set by the strength of the strong nuclear force The strong nuclear force holds the nucleus together by exchange of “gluons”

8. Quarks Protons and neutrons are each made up of 3 quarks Neutron Proton uud udd Up u Down d Electric charge +2/3 -1/3 The quarks are held together by gluons, ripples in the strong field

10. The Standard Model 22nd June 2011LHC physics Forces Matter particles Masses & potentials (Untested)

11. The Matter Particles u Quarks d c s t b Leptons νeνe νμνμ ντντ e μτ Charge +2/3 Feel the strong force Don’t feel the strong force Charge -1/3 Charge -1 Charge -0

12. The Force Particles WZ γ g Gluon Strong Nuclear Weak Nuclear Photon Light Electromagetism Key Concept: Interactions occur via exchange of particles

13. What the world is made of Matter Particles u Quarks d c s t b Leptons νeνe νμνμ ντντ e μ τ Force carriers WZ γ g  Particles: commonplace and exotic  This is the periodic table of the subatomic world Out there? h G

15. Key Equation Energy Mass Speed of Light 2 Lorentz Velocity factor Heavy particles? Large energy

16. v/c Key Equation

17. Note concerning “high energy” Spark could jump 5000 km in air (~radius of The Earth)

18. Key Equation Momentum Mass Speed Lorentz Velocity factor Exercise? Prove: E 2 – p 2 c 2 = m 2 c 4

19. WHAT WE KNOW WE’RE MISSING…

20. Scientific questions Where do the particles get their mass from? Where has all the anti-matter gone? What is dark matter made of? What else is out there?

21. Anti-matter predicted Bristol boy Paul Dirac 1902-1984 Remembered in Westminster abbey Discovered the equation of the electron Predicted the existence of its nemesis: the “anti-electron”

22. Anti-matter found Carl Anderson finds anti-electron in cosmic rays

23. Where has all the anti-matter gone? Matter and antimatter should have been created in equal amounts Subtle differences between matter and anti-matter will be investigated at the LHC High energy collisions create both in approximately equal amounts Where are the anti-planets?

24. DARK MATTER? Hubble telescope: 96% of the universe is NOT made of atoms Invisible “Dark matter” dominates Lots of circumstantial evidence Not dark matter

25. “Seeing” dark matter?

26. Mass and the Higgs Boson In this analogy the Higgs Boson is a treacle-ball – something which allows us to see the treacle itself Endows space with a kind of all-pervasive sticky-treacle Interactions with this treacle gives mass to particles They then travel slower than the speed of light The Higgs Theory High energy collisions ought to make Higgs Bosons

27. Current status Experiments working beautifully (just as well) Rediscovered all known particles (100 years of physics in 10 months Breaking new ground every day (nobody has explored where we are) Starting to constrain interesting theories Energy and rate of collisions increasing Great things expected in next couple of years

28. SOME EXTRA STUFF

29. WHERE WE ARE NOW

30. THE STORY BEHIND THE STORY Three examples

31. Why energetic collisions? A young man at a Swiss patent office, circa 1905 Energy Matter EnergyMass Speed of light Exchange rate: c = 299 792 458 meters/second

32. Invisible mass Visible mass Bullet

33. “Seeing” dark matter “Missing” transverse momentum

34. Switch on… CMS LHCb ALICE

36. CERN European Laboratory for Particle Physics Map © Google World’s largest particle physics laboratory Joint venture started in 1954 Multi-national laboratory on Swiss-French border Collaborators include many UK universities

37. Example (1) December 2008

38. End of the world: truth or fiction? LHC to turn on Physicists very excited about this Extreme outside chance that it MIGHT produce tiny tiny tiny black holes (safe!) Eating 27 Big Macs is not desirable Right Wrong Micro-black holes would immediately evaporate End of the world never possible! Experiment is actually perfectly safe

39. Example (2) November 2010

40. Recreate the Big Bang truth or fiction? Colliding Lead Ions Temperatures 1 million times that of the sun Not recreating the big bang Right Wrong Recreating the CONDITIONS of the very early universe Does not tell us of the ORIGIN of the universe

41. Example (3) April 2011

42. Truth or fiction Could have been indicative of something interesting (mass-giving “Higgs” particle) Unusual feature observed in data New particle not confirmed Truth Fiction Not a “God particle”

43. So…. what will the LHC tell us? Why particles have mass What “Dark Matter” is made of Where the anti-matter went The origin of the universe God’s favourite particle

44. Foot on the accelerator… Energy v / c Lorentz velocity factor Speed of light Mass Velocity factor

45. WHAT IS A LARGE HADRON COLLIDER? Big machine It bangs them together Class of particle (includes proton)

46. Our mission 1.Understand the basic building blocks of nature 2.Build a Hadron Collider 3.Address the unanswered questions of physics 4.Correct some misconceptions

47. ATLAS Segment of detector

48. The accelerator Magnets bend them in a circle Electric waves speed particles up

49. Source of protons? Hydrogen gas Hydrogen molecules Electron “gun” Electron cloud Protons

50. Speed up and bend e-e- Accelerate Bend E-field B-field

52. Blue Peter guide  Take some protons Lots of these in nature!  Make them move (very fast)  Bang them together It’s good to stand back at this point  Photograph the debris Your camera-phone may not be fast enough!

53. At four places the beams intersect Collision points

54. Fruit cocktail of collisions Produce ALL types of particles at that energy

55. The detectors are like digital cameras Very large cathedral-sized Precise: better than hair-width accuracy Fast: 40 million snaps per second (Your camera-phone probably isn't up to this) Built by Collaborations: constructed by hundreds of physicists, technicians, engineers

56. Local interest … Robotic assembly of precision silicon tracker Summer 2004 to Summer 2005

57. P The reconstruction of an early collision event