I. Antoniadis CERN IAS CERN Novice Workshop, NTU, 7 Feb 2014 1
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the Large Hadron Collider (LHC) Largest scientific instrument ever built, 27km of circumference >10 000 people involved in its design and construction at Accelerating Science and Innovation 4
Superconducting magnets at 1.9 o K = -271 o C (cooler than the outer space 2.7 o ) Several thousand billion protons Each with the energy of a fly Orbit 27km ring 11000 1 times/sec A billion collisions a second Accelerate protons at 0.99999999 x the speed of light 5
The Hottest Place in the Galaxy Particle collisions create (within a tiny volume) temperatures a billion times higher than in the heart of the Sun 6
Enter a New Era in Fundamental Science LHCb CMS ATLAS Exploration of a new energy frontier in p-p and Pb-Pb collisions ALICE LHC ring: 27 km circumference 7
The LHC is the world s most powerful microscope and also a telescope 8
Evolution of the Universe Big Bang Only particle physics can tell us what happened here 13.8 Billion Years 10 28 cm Today 9
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Major discoveries fundamental constants Thermodynamics : E = k B T k B = Boltzmann constant Special relativity : E = mc 2 c = speed of light Quantum mechanics : L h/e h = Planck constant 11
Inside Matter All matter is made of the same constituents What are they? What forces between them? 12
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The Standard Model of Particle Physics Proposed by Glashow, Salam and Weinberg Tested by experiments at CERN Perfect agreement between theory and experiments in all laboratories 14
The Standard Model = Cosmic DNA The matter particles : quarks and leptons The fundamental interactions Gravitation electromagnetism weak nuclear force strong nuclear force 15
The Standard Model of Particle Physics : electro-weak + strong forces Quantum Field Theory : Quantum Mechanics + Special Relativity Symmetry principle : gauge invariance Very accurate description of physics at present energies 17 parameters Several Nobel Prizes : Theory Glashow, Salam, Weinberg 79 Discovery of W ±, Z at CERN Rubbia, Van Der Meer 84 Theoretical consistency t Hooft, Veltman 99 Asymptoyic freedom of strong force Gross, Politzer, Wilczek 04 16
CERN 2009 : 50 years of Nobel Memories in High Energy Physics 17
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The Standard Model = Cosmic DNA The matter particles : quarks and leptons Where does mass come from? The fundamental interactions Gravitation electromagnetism weak nuclear force strong nuclear force 20
Why do Things Weigh? Newton: Weight proportional to Mass Einstein: Energy related to Mass Neither explained origin of Mass 21
Mystery of mass Elementary particles have a mass - matter : obvious - mediators of the weak force : also high mass short range force Origin of mass of elementary particles new type of particles (besides matter and forces) Brout-Englert Higgs mechanism 1964 Warning : mass of nucleus has different origin dynamical generation due to the strong force) 22
Why do Things Weigh? Newton: Weight proportional to Mass Einstein: Energy related to Mass Neither explained origin of Mass Brout-Englert Higgs mechanism at least one new particle: Higgs 0 boson (scalar) particle masses through interaction with the Higgs field Its discovery was one of the main goals of LHC 23
Higgs field: as a snowfield Skier moves fast: Like particle without mass e.g. photon = particle of light Snowshoer sinks into snow, moves slower: Like particle with mass e.g. electron The Higgs Boson: Like the snowflake Hiker sinks deep, moves very slowly: Particle with large mass 24
Without Higgs there would be no atoms Electrons would escape at the speed of light weak interactions would not be weak Life would be impossible: everything would be radioactive Its existence is a big deal! 25
Excellent LHC performance Number of events = Cross section x Luminosity 26
LHC: study the elementary particles and their interactions proton beams Acceleration of two beams of particles (e.g. protons) in bunches close to the speed of light and collide these bunches Today: 1400+1400 bunches Each bunch: 100 billions protons colliding protons interacting quarks The colliding protons break into their fundamental constituents (e.g. quarks). These constituents interact at high energy: (new) heavy particles can be produced in the collision (E=mc 2 ). The higher the accelerator energy, the heavier the produced particles can be. These particles then decay into lighter (known) particles: electrons, photons, etc. production and decay of a new particle By placing high-tech powerful detectors around the collision point we can detect the collision products and reconstruct what happened in the collision (which phenomena, which particles and 27 forces were involved, etc.) 1
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July 4 th 2012 The discovery of a new particle 29
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François Englert Peter Higgs Nobel Prize 2013 32
Open Questions within & beyond the Standard Model What is the origin of particle masses? due to a Higgs boson? Why so many types of matter particles? LHC LHC What is the dark matter in the Universe? LHC Unification of fundamental forces? Quantum theory of gravity? LHC LHC 33
ALICE: Primordial cosmic plasma ATLAS: Higgs and dark matter CMS: Higgs and dark matter 34 LHCb: Matter-antimatter difference
The Particle Higgsaw Puzzle Is LHC finding the missing piece? Is it the right shape? Is it the right size? 35
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How do Matter and Antimatter Differ? Dirac predicted the existence of antimatter: same mass opposite internal properties: electric charge, Discovered in cosmic rays Studied using accelerators Matter and antimatter not quite equal and opposite: WHY? Why does the Universe mainly contain matter, not antimatter? Experiments at LHC and elsewhere looking for answers 37
Dark Matter in the Universe Dark Matter in the Universe Astronomers say that most of the Astronomers tell matter us that most in the of the Universe matter in the is invisible universe is invisible Dark Matter LHC will look for it We will look for it with the LHC 38
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Classic Dark Matter Signature Missing transverse energy carried away by dark matter particles 40
Unify the Fundamental Interactions: Einstein s Dream but he never succeeded Unification via extra dimensions of space? 41
Gravity force Newton s law: force decreases with the area 42
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Energy evolution of the three force inverse-intensities Supersymmetry unification of forces at around 10 16 GeV 46
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