ATLAS experiment at the CERN Large Hadron Collider

Transcription

1 ATLAS experiment at the CERN Large Hadron Collider Peter Watkins, Head of Particle Physics Group, University of Birmingham, UK

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

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

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

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

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 Dark matter Extra dimensions of space Suggested by superstring theory Microscopic black holes The LHC experiments can look for all of of these. Also sensitive to to something completely different

10 The Large Hadron Collider (LHC) Mont Blanc Geneva Airport 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

11 Building the LHC In the main ring: 1746 superconducting magnets including m 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 The protons will reach % speed of light, and go round the 27km ring 11,000 times per second planet

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

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19 Electromagnetic Calorimeter

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

21 Muon Detectors

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23 E2 = p2c2+ m2c4

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

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

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32 50 magnets repaired 3 km of beam pipe cleaned

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

34 Z boson candidate

35 Summary Many people are interested in the LHC and the key ideas are widely accessible The 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 audience We need your help to do this to an even wider audience!

36 Thanks for listening