Fermilab Public Lecture

1. Fermilab Public Lecture The LHC Voyage Of Discovery Dan Green Fermilab

2. What is Particle Physics? Particle physics is the modern name for the centuries old effort to understand the laws of nature. It aims to answer the two following questions: What are the elementary constituents of matter ? What are the forces that control their behavior at the most basic level? Physicists continue to ask these questions since they have never really grown up. Experimentally: Make particles interact (accelerators) and study the produced particles. E=Mc2, using collision energy to make new, heavy particles. Measure the energy, the direction and the identity of all these reaction products as precisely as possible (detectors).

3. What is the Universe Made of? Early speculation on the building blocks, 500 BC

4. Atoms and Simplicity, 1869 All the complexity that we see in the World, with it’s 92 elements, comes from the simplicity of arranging electrons and protons in atoms. The periodic table groups elements with equal number of outer orbital electrons, for example noble gases. Lesson: predictions for missing elements.

5. Electrons - 1897 Accelerate in electric field, deflect in magnetic field and observe by having the e interact in a detector – the basic steps. Lesson: We can see electrons with our own eyes!

6. Nuclei – Rutherford, 1908 • Rutherford established the structure of the atom • by scattering particles off the atoms, • seeing wide angle deflections in a detector • Lesson: infer structure by scattering. • Atoms have small, positively charged nuclei, 100,000 times smaller than the electron distribution! • Students and scintillation……

7. Going Smaller and Simpler Nuclei are all made up of just neutrons and protons. Looking more closely, they in turn are made up of quarks. Quarks are fundamental ! ? To look closer we need higher energies. We use E = mc2 (Einstein) and we quote mass in energy units.

8. What are the Forces ? - Gravity “Of Newton with his prism …. A mind for ever voyaging through strange seas of thought”. “I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.” Lesson: gravity is universal – on earth (apples) as in the heavens (satellites) – a unification! Sir Isaac Newton

9. Electricity-Magnetism Maxwell in 1862 unified electricity and magnetism, and in so doing predicted a wave going at the speed of light, thus explaining light. Lesson: unification may predict new phenomena.

10. The “Weak” Interaction Curie in 1895 discovered that the elements were not eternal and indivisible, but changes occurred by “radioactive decay”. Elements can be transmuted ! Much later, 1982, we found that the weak interaction and the electromagnetic were unified. Lesson: forces tend to unify at high energies/temperatures or short distances .

11. Interactions in the Standard Model Matter particles interact via the exchange of force particles boomerang? Nuclei- need a strong interaction to overcome coulomb repulsion of the protons. “Gluons” are the force carriers

12. Force Particles Matter Particles The “Standard Model” - SM All force carriers, photon (EM), gluons (strong), gravitons (gravity) are massless EXCEPT the W,Z (weak force) – why is that? The LHC was designed to find the answer. You are here Predictions: b, t, vτ seen at Fermilab

13. Is the SM the End of the Story? • In the SM all particles have no mass, like the photon, and move at the speed of light! Not… • So we postulate the “Higgs boson” which gives mass to each particle of the SM. • Without a Higgs boson, our calculations for collisions begin to fail at a mass around 1 Trillion eV (TeV). This defines the “terascale” of mass – the TeV scale – where new Physics must emerge. • The Higgs by itself is not enough. Postulate a “super-symmetry” to solve the remaining problems of the Higgs. • What about our inability to incorporate quantum gravity? Postulate 10 dimensions! More later. • What about Dark Matter and Dark Energy – which are 96% of the Universe by weight? No Standard Model particles exists to explain them. Oh my!

14. Why the LHC ? • Many of the Standard Model problems point to the mass scale of 1 TeV. • The Large Hadron Collider, LHC, at CERN, in Geneva Switzerland was designed specifically to decisively confront that mass scale. • It is Large, 26 km circumference, uses Hadrons, protons in this case, and it is a Collider, bashing protons on protons head on = LHC. Geneva airport

15. High energies allow us: To look deeper into Nature (E  1/size), (“powerful microscopes”) de Broglie To discover new particles with high(er) mass (E = mc2) To study the early universe (E= kT) Einstein Boltzmann Particle Accelerators and the LHC Revisit the earlier, hotter, history of our Universe , searching for a new simplicity (“powerful telescopes”) by observing phenomena and particles no longer observable in our everyday experience.

16. The History of Our Universe proton-proton collisions at the LHC correspond to conditions here; time, temp and energy. The LHC is a time machine! energy, temp time

17. The LHC Beams are Energetic The LHC and its experiments are arguably the most complex scientific instruments ever built – of necessity if we are to confront the TeV mass scale decisively. The energy stored in the LHC beams would melt 1T of Cu. This is 200 times the Tevatron total beam energy. The energy in the magnets would melt 50T of Cu. Caution is needed.

18. The LHC is a Big Step in Mass The gain in “mass reach” is not just the factor of 3.5 in proton energy w.r.t. Tevatron. At the interesting TeV mass scale the reaction rate is a factor at least 10000 x greater at the LHC than at the Tevatron. Truly, the LHC is a machine for discovery, aimed at the TeV mass.

19. LHC Accelerator - Poised for Discovery wrt Tevatron (at design) Energyx 7 Reaction rate x 20 Large increase -> discovery • The LHC at 1.9 K is colder than the CMB • The LHC is the highest energy collider in the world • The LHC has the worlds largest cryogenic plant. • The LHC is designed to have the highest reaction rate of any collider, design value is 1 GHz.

20. World’s Largest Cryogenic Plant Deep space is at 2.3o above absolute zero. LHC operates at 1.8o to achieve a higher magnetic field. If normal magnets used, size would be 4x and power used would be 40x!

21. Extremely High Vacuum “Store” beams for ~ 10 hours. Protons travel ~ 10 billion km around the LHC ring ~ round trip to Pluto -> need a good vacuum

22. It’s Difficult – Rare Processes At design operation, there are 1 billion interactions per second to examine. In order to decisively study the 1 TeV mass scale, we need to examine a total of 10,000 trillion interactions. We are only 1 % of the way there at present and at ½ the design energy. We are just starting the long voyage.

23. ATLAS and CMS – at the Leading Edge Each detector is like a 100 megapixel camera which takes 40 million pictures per second. The largest and most complex scientific instruments ever built.

24. World’s Largest Collaborations There are 4 experiments at the LHC. The 2 general purpose detectors, ATLAS and CMS, have formed the largest scientific collaborations ever attempted. They function well because they have a common language and goals – Physics.

25. The CMS Collaboration It takes a collaboration of this size to fully address the physics. The US is the largest national group in CMS – about 1/3. FNAL is the second largest group in CMS, second only to CERN. FNAL is also the host for US CMS

26. US Physics and the LHC

27. CMS – Timeline, “Laying the Keel” • It took almost 20 years to design, construct, test, install and commission CMS with a very large team of scientists and engineers. 1993 - 2003

28. CMS Magnet The magnet is like a prism – bending the particles with more energy by less. The most expensive single device in CMS. The world’s largest solenoid.

29. Precision Tracking 200 m2 of Si with 75 million channels. A factor > 10 increase in complexity w.r.t. previous experiments. Spatial resolution of 0.0008 “ precisely determines particle trajectories in the magnet and therefore energies.

30. Crystals – Energy Measurements More than 60,000 crystals manufactured with <1 % tolerances in response. Needed for precise, redundant measurement of electron energies.

31. Data Analysis -It Takes a “Grid” Fermilab operates the national computing center for US CMS CMS produces 1 million DVD of data per year

32. How Do FNAL Physicists Participate? CMS is 4500 miles away. Can we ‘do physics” here? Yes indeed, all physicists are “remote” . At CERN you are 20 km away and the detector is 100m underground and inaccessible. We built the “Remote Operations Center” – ROC - and the “LHC Physics Center” - LPC. Stop by during the reception! The sun never sets on CMS. ROCs at CERN, DESY/Hamburg, FNAL and IHEP/Beijing.

33. Underground Experiment Cavern Late 2004 the “dry dock” 100 m underground

34. Spectacular Operations – “The Launch”

35. World’s Largest Solenoid 4 T, 3 GJ ~ 600 kg of TNT stored energy Feb., 2007

36. The Press Was There

37. Looking Back in Time at the LHC We make, in a tiny region of space, interactions at temperatures a million times hotter than the center of the sun. These temperatures correspond to a time a billionth of a second after the big bang. To set the scale, one TeV is the energy of a flying mosquito – but concentrated into a region of space 10,000 billion times smaller. An enormous energy density.

38. “The Shallows” – Shakedown Cruise In 2010, CMS measured all the particles of the Standard Model – some shown here 1960 1970 1980 ??

39. Into “Deep Waters” For every 10,000,000 W events produced you make at most 1 Higgs, which can then decay into 2 Z bosons, for example. It is still early days.

40. Higgs Decay to Z+Z? What a Higgs decay into 2 Z bosons which subsequently decay into 2 muons each would look like in CMS http://lbne2-docdb.fnal.gov /0040/004099/002

41. Into Uncharted Seas Once past the “shallows” and on into the deeps, what strange beasts may appear…. Terra incognita

42. Dark Matter ? You are here There is no known candidate for Dark Matter. Dark Matter is a stable, neutral relic particle from the earliest moments after the Big Bang – wonderful new physics.

43. Dark Matter and Colliding Galaxies Galaxy has a visible component and a dark component which interacts only gravitationally. Colliding galaxies show the different interactions of the neutral Dark Matter and the visible matter, which has Electromagnetic interactions.

44. Dark Matter Searches -“Full Court Press” Produce it Scatter it Observe it LHC FNAL annihilate These 3 could converge, making a tremendous scientific breakthrough

45. Super - Symmetry (SUSY) The lightest SUSY particle (LSP) is stable and would explain Dark Matter . A LSP mass of ~ 1 TeV yields the observed relic abundance of Dark Matter particles, 23 % ! SUSY also predicts the Grand Unified Theory (GUT) of forces where the 3 Standard Model forces unify at very high energies.. SUSY doubles the number of particles. Each Standard Model particle has a partner

46. SUSY at LHC For all the good features, many physicists like SUSY – but Nature is the final arbiter. A typical SUSY pair in CMS would have large unbalanced momentum (LSP escapes without leaving energy in CMS). Limits at the LHC are approaching 1 TeV. Stay tuned !

47. Gravity and SM Forces 100 years after GR (Einstein), it appears that point particles are not possible, but rather strings existing in many (10) dimensions, with those > 4 curled up into tiny size. Gravity is very, very weak – a small magnet can overcome the whole Earth and pick up a nail. Is that because gravity spreads out and dilutes in the additional dimensions? A completely naïve classical extrapolation of gravity comes close to the GUT mass scale. Is that a hint of more unification?

48. Gravity ? – Not in the SM • Extra dimensions ? • Are those dimensions observable? At the LHC we will look for extra dimensions. Perhaps we can push a particle to disappear into the unseen dimensions. • We are presently setting limits on the mass scale of a few TeV

49. Forces and Unification GUT “We shall not cease from exploration and the end of all our exploring will be to arrive where we started and know the place for the first time…. A condition of complete simplicity…. And all shall be well.” – T.S. Eliot The LHC program “has legs”. In 2014 the energy will double, opening up a higher mass reach. The interaction rate is planned to increase 10 fold, allowing study of rarer processes – a 25 year program of research has begun. TOE Energy

50. Well Documented – Read More