Atom Smashers Particle Accelerators and Detectors Mats Selen, UIUC

1. Atom SmashersParticle Accelerators and DetectorsMats Selen, UIUC • What’s the motivation ? • How to build a particle accelerator. • How to build a particle detector. A great web site with lots of links is: http://pdg.lbl.gov/particleadventure/english/index.html

2. Small indivisible “Atoms” There are many different kinds of atoms Elements (Periodic Table) There are lots of elements Nucleus (protons, neutrons) and electrons We can make “other” stuff (not made of protons neutrons and electrons) Everything madeout of quarks & leptons We don’t really understand this at afundamental level (Standard Model hastoo many free parameters) Smash More Atoms ! What’s the Motivation ? • Try to make sense of the way the Universe works • Look for simple explanations to complicated looking observations ! Complication Simplification There is lots of different “stuff” on earth

3. e e e e e e e e e e Electrons are easy: Just heat up a filament e e e e e e + - ENERGIZER ENERGIZER + + + + + + + + e e e e Protons are also quite easy: Ionize hydrogen e e e e - + How to build a Particle Accelerator First get some particles:

4. VanDeGraaff Accelerator + | + + + + + + + + + + + + + + ENERGIZER 10,000,000,000 voltbattery + + + + + Now Accelerate Them We’d like to give them lots of kinetic energy (lets say 10 GeV) Do VdG & bubble demo This can’t provide enough energy(only a few million volts) ! Need bigger voltage (and a vacuum system) !!

5. + + + + + | | | | | + + + + + ENERGIZER ENERGIZER ENERGIZER ENERGIZER ENERGIZER Linear Accelerator

6. - - - + + + ENERGIZER + Linear Accelerator

7. - - - + + + ENERGIZER + Linear Accelerator

8. ENERGIZER + Linear Accelerator - - - + + +

9. ENERGIZER + Linear Accelerator - - - + + +

10. ENERGIZER + Linear Accelerator - - - + + +

11. - - - + + + RF + Linear Accelerator

12. Some Examples LINAC at Bates Lab (MIT)(0.5 GeV) LINAC at Fermilab(0.4 GeV)

13. A Bigger Example SLAC (Stanford)(50 GeV)

14. Small linear accelerator + But some people like to recycle... • Have the particles go through the same accelerator cavitymany times Circular “track”(high-vacuum beam-pipe) This is called aSynchrotron Key ingredients: Need to make particles go in a circle Need to keep everything synchronized

15. Magnetic field “north” points into screen X X X X + | E X X X X X F = qE F + + v + X X X X X q F F X X X X X X ENERGIZER ENERGIZER X X X X X q q X X X X X v X X X Forces on Charged Particles • Both electric and magnetic fields influence the motion of charges. E/m demoTV demoGeiger demo F = qv x B

16. bending magnet Accelerating section Focussingmagnets Vacuum tube (beam pipe) Synchrotrons

17. Booster (8 GeV) Fermilab Main Ring (150 GeV) Tevatron (1000 GeV)

18. - 2000 GeV 1000 GeV 1000 GeV + A slick trick Two for the price of one

19. NOW LEP 200 GeV e+ e- In 5-6 years LHC 14000 GeV p p CERN

20. LEP Tunnel

21. + - How to build a Particle Detector Ideally, we want to measure everything (E, Px, Py, Px) about every particleproduced in the “collision”. Charged Particles Neutral Particles

22. + - Most Common Approach(for colliding beam experiments) Detector “package” looks like a beer can

23. Vertex Detector to measure theposition of charged particles close totheir point of creation. Solenoid (Magnet) (Makes charged particles curve,which tells us their momentum) Drift Chamber to measure the path of charged charged particles. Low density…mostly gas…so particles don’t notice it much. Calorimeter to measure theenergy of neutral particles. High density…particles often stop here. The Parts

24. m+ e- e- e- detect electron + + How it works • All of the parts work more or less the same way: • Charged particles ionize the material they pass through, and we can detect signs of this ionization. 1) Geiger counter

25. m+ scintillation e- e- e- + + + How it works • All of the parts work more or less the same way: • Charged particles ionize the material they pass through, and we can detect signs of this ionization. 2) detect photon Scintillator counter

26. p m Lets Try It • We don’t have an accelerator handy so lets look at cosmic rays: Cloud chamber

27. Wrapped scintillator oscilloscope Photo-multiplier Scintillation Detector • Photons are produced in the plastic by scintillating molecules when a cosmic ray muon whizzes through it. • These photons are detected by a photo-multiplier tube, and result in pulses on the oscilloscope. Singlescoincidencebeta

28. Concluding Remarks • The pursuit of High Energy Physics is motivated by a quest for fundamental understanding. • Current accelerator and detector technology is very cool.

29. The Periodic Table

30. Look carefully The Periodic Table Explained ? proton neutron electron

31. This is about 500 times too big The nucleus is much smaller than the atom Even so, the nucleus contains > 99.9 % of the mass of the atom !

32. 4 x He = 16.01 u Mass difference = 0.01 u = binding energy E = mc2 sure Energy vs Mass He (m=4.0026 u) O (M=15.9995 u) So energy is the same as mass somehow ?? Units

33. KE1 KE2 Mass from Energy

34. Mostly KE New Mass + KE Mass from Energy Ebefore = Eafter

35. E = m Physicists are sloppy - 1eV= kinetic energy of an electron acceleratedthrough a 1 volt potential difference 1 voltbattery e- ENERGIZER + Units E = mc2 Preferred unit of Energy/Mass = GeV This is a small amount of energy (more appropriate for chemistry) 1GeV=109 eV (a billion eV) (about the mass of a proton…appropriate scale for us)

36. It gets more complicated again... fj D*2 Lc f3 f2 B h Sc w D* f4 f’2 W p2 a4 p f0 K* K3 S r h1 a1 a0 Bc h0 f1 K2 D1 w3 D2 Bs Ds K L K*2 w D K1 a2 f h’ K*4 B* K*3 r3

37. + 2/3 -1 t m e top up charm - 1/3 0 ne nt nm strange down bottom quark charge lepton charge quarks & leptons

38. + 2/3 - 2/3 u c t u c t - 1/3 + 1/3 d s b d s b anti-proton proton neutron D0 Bs p+ quarks & anti-quarks (baryons) Now we can easily build any ofof the particles we have discovered(and predict some we haven't) (mesons)

39. Example: CLEO

40. = 2 X Example: L3

41. Vertex Detector (CLEO)

42. Drift Chamber

43. Calorimeter

44. Solenoid