2. Recreating the Big Bang with the Large Hadron Collider at CERN Dr David Evans The University of Birmingham 24 th February 2009

3. 2 Somewhere in Switzerland… Situated on the Swiss-French border, near Geneva Is the World’s largest physics laboratory

4. 3 CERN Deep underground, we have built the World’s largest machine Geneva French Alps Which will accelerate sub-atomic particles to 0.999999991 the speed of light …. The Large Hadron Collider (LHC)

5. 4 Large Hadron Collider …. and collide them together in four cathedral-sized caverns around the 27 km ring. Creating sub-atomic explosions, and conditions that existed less than a billionth of a second after the Big Bang. In 4 massive particle detectors Up to 600 million times per second

6. 5 The LHC Let’s start at the beginning…..

7. 6 Building Blocks of Matter  All matter around us is made of atoms.  Atoms consist of a positive nucleus (containing 99.98% of the atom’s mass) and a cloud of electrons.  Nuclei consist of protons and neutrons.  The protons and neutrons are made of three quarks. in metres We know

8. 7 Elementary Particles  Protons and neutrons are made from two types of quarks: Up (u) and Down (d).  u-quarks have electric charge +2/3 while d-quarks have charge –1/3 (electron has electric charge -1 in these units). U +2/3 U d -1/3 Proton U +2/3 d -1/3 d Neutron

9. 8 Family of Particles So, there is a family of particles: Up quark (u)Down quark (d)Electron (e - )Electron neutrino ( e ) Mass ~ 0.003~ 0.006 = 0.0005 < 10 -8 ? (relative to the mass of a single proton) Everything around us (the whole Periodic Table) is made up of these four particles. So, that’s nice and simple then!

10. 9 BUT…. leptons quarks up down e e     strange charm bottom top Nature supplies us with two extra families that are very much heavier: We don’t know why!

11. 10 Virtual Particles The forces between fundamental particles are mediated by virtual carrier particles. For example, the electromagnetic interaction between two charged particles (say two electrons) is understood to be due to the exchange of virtual photons. A virtual particle is one that violates conservation of energy, but only for a short period of time (  t < ħ/  E) – it ‘borrows’ energy from the vacuum.

12. 11 The Forces Force Range Mediator Rel. Strength Gravitational long graviton (massless) ??1 Electromagnetic long photon (massless) 10 35 Weak short W, Z bosons (heavy) 10 33 Strong short gluons (massless) 10 38 Gravity – stars, planets etc. Electromagnetic – atoms, electricity etc. Weak force Strong – binds quarks (residual force binds nucleons in nuclei) Weak – beta decay, how stars generate energy

13. 12 The Standard Model u d s c b t e e     quarks leptons } }

14. 13 The Weak Force u d s c b t e e     quarks leptons } } W+W+ W-W- Z0Z0

15. 14 The Electromagnetic Force u d s c b t e e     quarks leptons } }  Photon

16. 15 The Strong Force u d s c b t e e     quarks leptons } } g gluon Gravity too weak to even consider at the atomic scale

17. 16 Antimatter  Every fundamental particle has its antiparticle.  These have the same mass but opposite charge. e-e- e+e+ u +2/3 u -2/3 electron positron up quark up anti-quark Etc.

18. 17 Antimatter If a particle and antiparticle each of mass, m collide they annihilate with the production of energy, E in the form of radiation – the total mass (2m) is converted into energy). – E = 2mc 2 (using the famous equation: E = mc 2 ) u +2/3 u -2/3 The opposite is also true; given enough energy, one can create matter with equal amounts of antimatter.

19. 18 Big Bang So far, our experiments show that equal amounts of matter and anti-matter are produced when energy is converted into matter – for every up quark created, an up anti-quark is also created etc. So, equal amounts of matter and anti-matter should have been created during the Big Bang. But we live in a universe made from matter. Where did all the anti- matter go?

20. 19 Other Questions – What is Mass? In the mid 1960s, British physicist Peter Higgs came up with a theory on why some particles have mass. He proposed a new heavy particle, now called the Higgs, which generates a Higgs field. Particles who ‘feel’ this field gain mass. Light particle don’t feel this field strongly, heavy particles do.

21. 20 Higgs The heavier it is, the more force is needed to accelerate it. The Higgs field makes it more difficult for particles to be accelerated thus giving them mass. It’s a bit like walking through treacle! Just one problem with the theory … We haven’t seen the Higgs yet. Demonstration Mass is really a measure of how difficult it is to accelerate an object (F=ma).

22. 21 Dark Matter The visible Universe (made from u, d, e, ) only accounts for about 4% of its measured mass. What makes up the rest?

23. 22 Many More Questions … What is mass? 4 forces? 12 matter particles? What about gravity? Where did all the antimatter go? Mini black holes? How many dimensions? What about the other 96% of the universe ….. Why no free quarks?

24. 23 How do we find answers? …. ….powerful particle accelerators

25. 24 How do we try to Answer these Questions? By colliding particles at fantastic energies and studying what comes out. At the LHC, the quarks (in protons) will collide with energies that existed ~ billionth of a second after the Big Bang. Physicists at the University of Birmingham play leading roles in 2 of the 4 main LHC experiments: ALICE and ATLAS.

26. 25 Particle Accelerators Basic design is just like a TV –i.e. RF cavities apply accelerating voltage –Bending magnets (dipoles) steer the particles –Quadrupole magnets focus the beams A charged particle (q Coulombs) dropping through a potential, V Volts acquires energy E=qV (1 Volt gives energy of 1eV). Unlike a TV (V ~ 10,000 Volts) the LHC at CERN will accelerate particles to 14 Trillion Volts.

27. 26 LHC Tunnel Now, being commissioned Now, being repaired!

28. 27 LHC - Facts 27 km circumference Each proton goes around the 27km ring over 11,000 times a second. Energy of proton beam in LHC > 0.3 GJ (family car travelling at 1000 mph) Energy stored in magnets > 1 GJ Super-conducting magnets cooled to ~ 1.9 K (colder than Outer Space).

29. 28 Why so Cold?  At LHC energies, we need huge magnetic fields to accelerate and steer the beams of particles – about 10,000 times that of a strong bar magnet.  Not possible with conventional magnets.  Need superconducting magnets.

30. 29 Back to Anti-Matter Can you make a bomb with anti-matter? In theory, yes – ½ gram of anti-matter would produce about the same energy as the Hiroshima bomb.  The LHC will produce about 100 million anti-protons per second.  Sounds a lot but 1 anti-proton only has a mass of 1.67x10 -27 kg (same mass as proton).  So, will take the LHC about 2 thousand million years to collect ½ gram of anti-matter.  We would need to be VERY patient!

31. 30 Detecting Particles Used Bubble Chambers in the old days Only 1 event / second Photos scanned by hand No selection on events

32. 31 Modern Detectors ATLAS Detector (one of the four main LHC detectors)

33. 32 What Am I Working On? It’s not all drinking coffee outside the CERN canteen! Or standing around… Waiting for the LHC.  I’m working on understanding the Strong Force.  how does it generate 98% of the mass of nuclear matter?  why are there no free quarks? Etc.  And trying to unlock the secrets of the primordial state of matter, the Quark-Gluon Plasma, which would have existed up until about 10 millionths of a second after the Big Bang.

34. 33 The Quark-Gluon Plasma Normal hadronic matter At extreme temperatures and/or densities hadronic matter ‘melts’ into a plasma of free quarks and gluons. This new state of matter would have existed up to about 10 millionth of a second after the Big Bang, and could be created in the core of collapsing neutron stars.

35. 34 How to Make a QGP Need very high energy densities Create sub-atomic volumes of hot, dense matter similar to conditions 10 -6 s after Big Bang Fireball must live long enough for phase transition to take place Collide lead ions (lead nuclei) at highest energies

36. 35 The Fireball Temperature of our fireball ~ 10 13 K i.e. > 1,000,000 times the temp of centre of Sun. Density ~ Great Pyramids crushed to the size of a pin-head – similar to neutron star densities (but much hotter!) T ~ 15,000,000 K

37. 36 What Happens ? Energy is converted into many quarks, anti-quarks and gluons. QGP lasts for about 10 -22 seconds Then thousands of particles are produced We have to study the QGP from this!

38. 37 The ALICE Detector ITS Low p t tracking Vertexing ITS Low p t tracking Vertexing TPC Tracking, dEdx TPC Tracking, dEdx TRD Electron ID TRD Electron ID TOF PID TOF PID HMPID PID (RICH) @ high p t HMPID PID (RICH) @ high p t PHOS ,  0 PHOS ,  0 MUON  -pairs MUON  -pairs PMD  multiplicity PMD  multiplicity 52 feet (16 metres) high, 85 feet (26 metres) long, and weighs about 10,000 tons ALICE in December 07 – photo by Simon Hadley, Birmingham Post

39. 38 Data & Computing Challenges Write data to tape ~ 1.2 Gbytes/sec (2 CDs/sec) Equivalent to writing the Encyclopaedia Britannica every two seconds ~ 2 Pbytes / year (3.3 million CDs worth – that’s a stack of CDs 3 miles high - >12 miles high for all LHC experiments) Computing requirements: ~ 50,000 PCs (3 GHz) x 3.3 million Concorde (15 Km) Balloon (30 Km) CD stack with 1 year LHC data! (~ 20 Km) Mt. Blanc (4.8 Km)

40. 39 Summary  Particle physics has discovered much about how the Universe works  Still many outstanding questions  The World’s largest machine (LHC) will add to this knowledge  Huge challenges ahead  But LHC will find new & exciting physics  We will learn more about the very early Universe  Birmingham will play an important role in this.  Thank you for listening.

41. 40 Particle Physics Spin- offs Medical Imaging Education Technology Computing Research For every £10 spent on NHS, only 1p is spent on particle physics. No, PET scanners, no MRS scans, no cancer killing particle beams etc. without particle physics