subatomic physics & astrophysics intimate connexion between very large and very small
TRANSCRIPT
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SubAtomic Physics &
Astrophysics
Intimate Connexionbetween Very Large
and Very Small
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Plan of Talk
• Research Interests at Toronto
• Standard Model of Particle Physics
• Puzzles
• Profound connexion between understanding of microstructure and macrostructure of universe.
• Solutions???? • Experiments
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Interest Groups @ UofT
• Experimental Particle Physics Origin of Mass, Structure of Proton ….
Large Projects: ATLAS, CDF, ZEUSBailey, Martin, Orr, Sinervo, Trischuk
6 Post Docs12 grad students
• Experimental CosmologyGeometry of Space-TimeLarge Project: BoomerangNetterfield - just starting !
1 grad student
• Theoretical Particle PhysicsOrigin of Mass, Structure of Hadronic MatterHoldom, Luke, O’Donnell
3 Post Docs4 grad students
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• Large Program In Astrophysics Galaxy Formation
Large Scale Structure of UniverseCosmic Background RadiationStellar Dynamics ...Bond, Martin, Kofman, Murray, Pen
25 visitor & fellows9 grad students
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Is the Universe Made of These?
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Quantum Forces
• In Quantum Field Theory, particles interact via:.
Exchange of virtual particles
Electrons interact by exchanging:
Virtual Photons
Quarks interact by exchanging:
Virtual Gluons
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Weak Interaction• A force very like electromagnetism; but
acts on Weak Charge
• In Fact, electromagnetism and weak forceare aspects of unified electroweak force
• Electric charge and weak charge are
related
• Three “force carriers”
W Z 0
W Z 0
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Higgs Boson
• Electromagnetism on its own can be made to give finite results for all calculations.
• Unified Electroweak theory gives infinite results for process like:
• Become finite if include new particle
Higgs boson
• Higgs makes massive, and actually generates masses of all particles. It is a quantum field permeating the universe.
W Z 0
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How Does Higgs Generate Mass?
• In vacuum, a photon:
has velocity c and has zero mass
• In glass a photon
has velocity < c , same as an effective mass
• This is due to photon interacting with
electromagnetic field in condensed matter
• By analogy can understand masses of particles
generated by Higgs Field in vacuum
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Grand Unification.
• At a high enough energy
electromagnetismweak forcestrong (colour) force
become aspects of Grand Unified Force
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The Universe is Expanding
Its ultimate fate depends on density of matter and energy
• If , the density of matter and energy is greater that a critical density the universe will start to contract
• If is less than the critical density, the universe will continue to expand.
• Usually measure the density in units of
• spherical space-time: contraction
• flat space-time: expansion
• hyperbolic space-time: expansion
0
0
c
00 0
02
8
3
c
G
H
0 1
0 1
0 1
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Experimental Mystery
• Density of Standard Model Matter
• If Universe is made of quarks & leptons
• Find
• Density of all gravitationally interacting matter
• Most of Universe is not Standard Model matter. Some kind of Dark Matter
B
B 0 1
B 0 05.
M 0 0 1.4 .
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Measuring
• Amazingly enough can measure
total matter/energy density in universe
• Measure temperature fluctuations in remnant of fireball from Big Bang.
0
0 1
Map of sky temp~ 3 Kelvin
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Boomerang: Measuring Fluctuations in Cosmic Microwave Background Radiation.
Gondola with temperaturemeasuring “telescope”
Flight path over Antarctica
Readying for launchMount Terror formsa backdrop.
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Need for Supersymmetry
• In Grand Unified Theories cannot Unify forces, unless postulate unseen form of matter
• Higgs mass runs away to Plank Scale• Three forces never have same strength
• Unless all particles have supersymmetric sparticle partners (of higher mass)
+Sleptons BosinosSquarksSpin 1 Spin1/2
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SUSY + Dark Matter
• Supersymmetric Particles are unstable
• Eventually decay chain ends in Normal matter + lightest SUSY particle
• Lightest SUSYparticle cannot interact withnormal matter
• Lightest SUSY particle good candidate for
Dark Matter
• Hope to produce
(SUSY - antiSUSY ) pairs and Higgs at
Large Hadron Collider
Susy Normal Susy
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How to Make Matter / AntiMatter?
LHC will be proton - proton colliderFermilab is proton - antiprotonHERA is electron - proton
Colliding high energy beams
Energy of beams transformed into mass of new particles
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Typical Accelerator Complex
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CERN Seen from the Air
• Tunnels of CERN accelerator complex superimposed on a map of Geneva.
• Accelerator is 4.3km in radius 50 m underground
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LHC Tunnel
This is an arc of the circular tunnelCircumference 26.7 Km
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Collider Detector @ Fermilab
Discovered thesix quark
Top - completes quark generations
UofT involved in upgrading silicon vertex detector
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Collider Detector @ Fermilab
Discovered thesix quark
Top - completes quark generations
UofT involved in upgrading silicon vertex detector
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Collider Detector @ Fermilab
Discovered thesix quark
Top - completes quark generations
UofT involved in upgrading silicon vertex detector
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ZEUS ep Collisions - Proton Structure
Experimental confirmationof equal strength of weak and electromagnetic forces at high energy
Electroweak Unification
ep Collisionseen in ZEUS
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ATLAS @ CERN LHC
Computer Simulationof discovery of Higgs Boson
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