1. ATLAS experiment at the CERN Large Hadron Collider Peter Watkins, Head of Particle Physics Group, University of Birmingham, UK p.m.watkins@bham.ac.uk

2. Point 1 activities and perspectives Marzio Nessi ATLAS plenary ATLAS plenary 2 nd October 2004 Large Hadron Collider (LHC)

3. Outline of talk Building blocks of the universeBuilding blocks of the universe Why do experiments at the LHC ?Why do experiments at the LHC ? LHC, ATLAS and collaborationLHC, ATLAS and collaboration Searching for a new particleSearching for a new particle Recent LHC newsRecent LHC news Acknowledgements – Acknowledgements – Many slides from LHC colleagues Many slides from LHC colleagues

4. 4

5. 10 -10 m (thickness of human hair ~ 10 -5 m) 10 -14 m10 -15 m< 10 -18 m The very small electron up quark down quark nucleus proton neutron

6. Fundamental Forces Gravity – solar system, galaxies …- extremely weak force Electromagnetic – atoms, electricity ….. - carried by photons Weak force Strong – binds quarks inside proton carried by gluons – beta decay and how stars generate energy - carried by massive W and Z bosons All forces are carried by particles !

7. Higgs boson?

8. The Higgs Boson One key objective of the LHC is to understand the origin of mass – is it due to a universal Higgs field? (A Higgs field everywhere with the Higgs boson as the force carrier?). Massless particles are not impeded by the Higgs field and, thus, travel at the speed of light. Analogy: Downhill skier experiences no drag by the snow field. Light particles interact weakly with the Higgs field and travel slower. Analogy: Snowshoes on the top of the snow field experience some drag. Heavy particles interact strongly with the Higgs field and travel very slowly. Analogy: Wading through the snow field is a big drag! We call this drag “Mass”.

9. What else is out there? Various ideas considered…Various ideas considered…  Dark matter  Extra dimensions of space Suggested by superstring theory  Microscopic black holes The LHC experiments can look for all of these. Also sensitive to something “completely different”

10. The Large Hadron Collider (LHC) The LHC is a 27km accelerator that collides counter-rotating beams of protons of up to 7 TeV. (Tev = million million eV) Energy densities similar to billionths of a second after the big-bang will be recreated at collision points CERN laboratory on Swiss – French border Mont Blanc Geneva Airport

11. Building the LHC In the main ring: 1746 superconducting magnets … including 1232 15m SC dipoles … weighing 27 tonnes each … producing 8.36 Tesla … and running at –270c … needs 700,000 litres liquid He … and 12 million litres liquid N 2

12. The fastest racetrack on the planet The protons will reach 99.9999991% speed of light, and go round the 27km ring 11,000 times per second

13. At four places the beams intersect Collision points

14. Hot spots too ! When the two beams of protons collide, they will generate temperatures 1000 million times hotter than the heart of the sun, but in a minuscule space

15. Four detectors at different points around the ring reconstruct the debris from the collisions

16. 7,000 tonnes 42m long 22m wide 22m high 2,800 Physicists 169 Institutes 37 Countries ATLAS Detector (About the height of a 5 storey building)

20. Electromagnetic Calorimeter

21. A basic calorimeter Total # of particles is proportional to energy of incoming particle Active detector slices produce a signal proportional to the number of charged particles traversing Basics The past Challenges Where to start? Detector Design Tracker Calorimetry Particle ID LHC detectors “Events” Final thoughts

22. Muon Detectors

24. E 2 = p 2 c 2 + m 2 c 4

28. Proton bunches collide 40 million times a secondProton bunches collide 40 million times a second ~25 proton-proton collisions occur each time~25 proton-proton collisions occur each time 1000000000 collisions per sec –1000000000 collisions per sec – 200 per second limit for recording 200 per second limit for recording Select the most ‘interesting’ collisions in few microsecondsSelect the most ‘interesting’ collisions in few microseconds Discovering a new particle The collision rate challenge

29. Searching for Rare Phenomena 9 orders of magnitude The HIGGS All interactions Number of collisions Collision energy

33. 50 magnets repaired 3 km of beam pipe cleaned

34. LHC status and plans Large Hadron Collider restarted in Nov 2009 and is working wellLarge Hadron Collider restarted in Nov 2009 and is working well World record was set for collision energy in December 2009World record was set for collision energy in December 2009 On March 30 th 2010 the collision energy was increased to 7 TeVOn March 30 th 2010 the collision energy was increased to 7 TeV Some early measurements already publishedSome early measurements already published Search for Higgs boson needs more collisionsSearch for Higgs boson needs more collisions

35. Z boson candidate

36. Summary Many people are interested in the LHC andMany people are interested in the LHC and the key ideas are widely accessible the key ideas are widely accessible The searches for new particles are only just beginning and will last for a decadeThe searches for new particles are only just beginning and will last for a decade We work on sharing the excitement of the project with the widest possible audienceWe work on sharing the excitement of the project with the widest possible audience We need your help to do this to an even wider audience!We need your help to do this to an even wider audience!

37. Thanks for listening