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Transcript of Quantum Phenomena II: Matter Matters Quantum Phenomena II: Matter Matters Chris Parkes April/May...
Quantum Quantum Phenomena Phenomena
II:II:Matter Matter MattersMatters
Chris Parkes April/May 2003
Hydrogen atomHydrogen atom Quantum numbers Electron intrinsic spin
Other atomsOther atoms More electrons! Pauli Exclusion Principle Periodic Table
Particle PhysicsParticle Physics The fundamental particles The fundamental forces
CosmologyCosmology The big bang The evolution of the
universe
Fundamental PhysicsAtomic Structure2nd Handout
Second Handout
http://ppewww.ph.gla.ac.uk/~parkes/teaching/QP/QP.html
The Structure of MatterThe Structure of Matter
Quarks have most of massQuarks have most of mass Electrons spatial extent and Electrons spatial extent and
determine chemical propertiesdetermine chemical properties
Fundamental ?Fundamental ? 450BC Empedocles, Aristotle450BC Empedocles, Aristotle
4 basic elements Similar philosophies in China / India
Democritus “Atoms & space”Democritus “Atoms & space”
1661 Boyle Elements1661 Boyle Elements …Medeleyev lots of them !
C19 Dalton, elements composed of atomsC19 Dalton, elements composed of atoms
nucleusnucleus Protons, neutrons….Protons, neutrons….
Lots more started turning up!Lots more started turning up! QuarksQuarks
Standard modelStandard model
"Young man, if I could remember the names of these particles, I would have been a botanist!”, Fermi
Looking at smaller scales Looking at smaller scales
Naked EyeNaked Eye 1010-4-4 m m Light MicroscopeLight Microscope 1010-6-6 m m Size of Atom Size of Atom 1010-10-10 m m Size of ProtonSize of Proton 1010-15-15 m m Size of quark, electron, neutrino..Size of quark, electron, neutrino.. 0 (so far..)0 (so far..)
Fundamental particles No constituents
Study using Study using Particle AcceleratorsParticle Accelerators Labs: CERN, Fermilab… Acelerators: LEP/LHC, Tevatron
Collide particles at high energiesCollide particles at high energies Look at what comes out !Look at what comes out !
•Collisions are Fixed target or colliding beam
• colliding beam uses all available energy
And accelerators:
•Linacs (straight) or synchotrons (circles)
•Particles are accelerated by electric fields
•Bent by magnetic fields
•Beams made to collide inside detectors
•Can keep particles travelling round and round in circle
•But lose energy, radiate photons, when travelling in a circle
CERN’s big accelerators
•27 km long tunnel,100m underground
•French/Swiss Border near Geneva
•1989 – 2000 Large Electron Positron collider (LEP), colliding beam synchotron
•2007 onwards Large Hadron Collider (LHC), proton collider
Particle Physics AcceleratorsParticle Physics Accelerators
Fermions & BosonsFermions & Bosons
We introduced spin for electron…but general We introduced spin for electron…but general particle propertyparticle property
Determines particle propertiesDetermines particle properties Half-integer spin particles – Half-integer spin particles – FermionsFermions
Fermi-Dirac Statistics Pauli Exclusion principle
Whole-integer spin particles – Whole-integer spin particles – BosonsBosons Bose-Einstein statistics No Exclusion principle, as many as you want in same state
Matter is made of the fundamental fermionsMatter is made of the fundamental fermions Forces are carried by the fundamental bosonsForces are carried by the fundamental bosons
Standard ModelStandard Model is theory which contains these is theory which contains these fundamental particlesfundamental particles
Fermions: Building blocks of matterFermions: Building blocks of matter
This is what everything around us is made ofThis is what everything around us is made of But there are more !
Proton: uudProton: uud Neutron: uddNeutron: udd electronelectron Neutrino given off in Beta decayNeutrino given off in Beta decay
rest mass electric charge other charges
in MeV/c2
“up” quark u 300 + 2/3 e colour & weak
“down” quark d 300 -1/3 e colour & weak
electron e- 0.5 - e weak
neutrino e v. small but >0 0 weak
QUARKS
LEPTONS
The first generation fermionsThe first generation fermions
All spin ½ particles
Forces of natureForces of nature
Forces mediated by particle exchangeForces mediated by particle exchange
e.g. electromagnetism :
photon exchange between electrically charged particles
Force acts on particles with that type of “charge”
Feynman Diagram
Bosons: Force CarriersBosons: Force Carriers
All particles feel gravity, graviton not discoveredAll particles feel gravity, graviton not discovered All particles have weak charge feel weak forceAll particles have weak charge feel weak force Electric charged feel emag.Electric charged feel emag. Only quarks feel strong force, confined, colour neutralOnly quarks feel strong force, confined, colour neutral
Force boson mass interaction charge relative strength range
in GeV/c2
Gravity graviton ?0? mass 10-39
Weak W+,W-,Z 80/91 weak charge 10-5 10-18 m
Electromagnetism Photon () 0 charge 10-2
Strong gluon (g) 0 colour charge 1 10-15 mThe four forces and their carriersThe four forces and their carriers
Spin 1, except graviton spin 2
Forces : some basic Forces : some basic consequencesconsequences
Strong Strong glues quarks to make protons / neutrons Glues protons / neutrons to make nuclei
ElectromagnetismElectromagnetism Bind electrons to nuclei Sticks atoms together to make molecules
GravityGravity Holds large lumps of matter together: stars, planets, galaxies
Weak Weak Radioactive decay Cross-generational couplings….
Feynman DiagramsFeynman Diagrams
We already saw one forWe already saw one for electron,positron electron,positron annihilationannihilation
Here is neutron decayHere is neutron decay
By following sets of rules, we can see if this By following sets of rules, we can see if this reaction will happenreaction will happen
Particle interactionsParticle interactions
Some basic standard model vertices:Some basic standard model vertices:
Anti-matterAnti-matter
Each particle has an anti-particleEach particle has an anti-particle e.g. electron / positron
Properties are oppositeProperties are opposite Opposite charge (and weak and colour) same mass and spin
Bubble Chamber photo,
A very old fashioned photographic form of particle detector
Electron & positron bending in magnetic field
Dirac Equation, 1930, relativistic version of Schrödinger for electrons,
but it seemed to have -ve energy electrons !
No, positive energy but anti-matter!
Anderson discovered in 1931
Some particles are their own anti-particles:
Photon, neutral pion
Dirac: “This result is too beautiful to be false; it is more important to have beauty in one's equations than to have them fit experiment.”
A typical modern particle A typical modern particle physics experimentphysics experiment
DELPHI experiment @ LEP collider
Particle and anti-particle Particle and anti-particle annihilate to pure energyannihilate to pure energy
m is rest massm is rest mass Add K.E. termAdd K.E. term Basis of most modern particle Basis of most modern particle
physics accelerator exptsphysics accelerator expts Smash highly energetic particle and
anti-particle together
E=mcE=mc22
or ratheror ratherEE22=(pc)=(pc)22+(mc+(mc22))22
dd
uu
vv
ee
ee
,
,
,
,
WW
ZZ
gluongluon
photonphoton
gravitongraviton
,
,
,
,
,
00
Particles and their anti-particles
1st generation fermions Bosons
Basic KinematicsBasic Kinematics
Apply what you have learnt about relativityApply what you have learnt about relativity e.g. particle A decays into particles B & Ce.g. particle A decays into particles B & C
Work in rest frame of particle A
ReactionReaction
momentum momentum
EnergyEnergy
2222
0
CBBBA
CBA
CB
mpmpm
EEm
pp
CBA
CBA
CB
mmm
pp
So particles go off back-to-back
and we must have enough energy to make them
Energy,momentum conservation – but energy includes rest mass
II Rabi
Three generationsThree generations
•Muon discovered by Street & Stevenson 1937 using Wilson Cloud chamber
….
•b quark was found in 1977, Fermilab
•top quark MUCH heavier (40x) found in 1995, Fermilab
•W/Z found at CERN 20 years ago
And ONLY 3 ! LEP from number of neutrinos
Bosons: graviton, W+,W- Z0, gluon, photon
+ anti-particles. all fermions found
Standard Model: one extra –the Higgs boson (H), responsible for mass
No gravity
Still to find…
Higgs Boson
?Graviton ?
Conservation LawsConservation Laws
Tell us which processes can happenTell us which processes can happen Short-cut for Feynman diagramsShort-cut for Feynman diagrams Conserved quantities in a reactionConserved quantities in a reaction
Same before – initial state As after – final state
1. Momentum vector, p2. Energy E, relativistic so due to momentum and rest mass3. Baryon number B
• Number of quarks remains constant4. Electric Charge Q
• Helpfully, most particles have charge as superscript on name• e.g. +
• Lepton number, for each generation: Le,L,L
Fundamental ParticlesFundamental Particles
Anti-particles have Anti-particles have opposite opposite propertiesproperties
e.g. Positron e+ has
Q=+1, Le=-1
Hence, particle-Hence, particle-antiparticle antiparticle combinations have combinations have zero everything!zero everything!
e.g. composite particle
made of dduu ,
0
Baryon number is fractional, so that proton & neutron have B=1
ConfinementConfinement Strong force very strong !Strong force very strong ! Quarks bound cannot break freeQuarks bound cannot break free
No free quarks Lower energy to produce new particles than separate quarksLower energy to produce new particles than separate quarks All particles observed have no net colourAll particles observed have no net colour
Electric charge has one type +, and its opposite -
Colour charge comes in three types: red, green, blue and their opposites: anti-red,anti-green anti-blue
Hadrons: where quarks hideHadrons: where quarks hide Hadrons are the bound states of quarks we Hadrons are the bound states of quarks we
observeobserve Controlled by strong force, remember leptons don’t feel this
Only colourless states can be madeOnly colourless states can be made1. Coloured quark and anti- that same colour quark
This is called a Meson (integer spin, hence a boson)
Most common mesons are the pions 0 ,+ ,-
2. ‘Mix’ three colour charges together This is called a Baryon (½ integer spin, hence a fermion)
Most common Baryons are proton & neutron
These are the basic first generation composite states:
Other HadronsOther Hadrons These last states only contained up, down quarksThese last states only contained up, down quarks Also have strange, charm, top, bottomAlso have strange, charm, top, bottom
Can make hadrons with these also ….hence very large number of combinations!
We will consider only the strange quarkWe will consider only the strange quark Next lightest quark after up,down Like a heavy version of the d quark, mass 500 MeV, Q=-1/3
Strange quark has strangeness =-1Strange quark has strangeness =-1 These states are unstable decay into proton, neutron, pions
Kaon mesons are counterparts of pions with s rather than d quark
Strange Baryons
Sigma , Lamda, Xi
(with spin ½)
(with spin 0)
Quark JetsQuark Jets
Don’t observe free quarksDon’t observe free quarks
Quarks form into composite Quarks form into composite states of two quarks states of two quarks (mesons) or three quarks (mesons) or three quarks (baryons)(baryons)
in particle detectors often in particle detectors often see showers of these see showers of these particles – particles – jetsjets of mesons of mesons and baryonsand baryons
Jet of mesons &BaryonsProduced from one initial high Energy quarkOr anti-quark
Jet of particles seen in trackingSystem of detector
Some Key PointsSome Key Points
Forces are due to exchange of the fundamental Forces are due to exchange of the fundamental force carrying bosonsforce carrying bosons
Photon,gluon,W+,W-,Zo (and presumably graviton)
Know the fundamental particlesKnow the fundamental particles Three generations of quarks and leptons
Don’t observe free quarksDon’t observe free quarks Confined in colourless hadrons
Added some more conservation lawsAdded some more conservation laws Energy, momentum, electric charge Baryon number, lepton number
Particle interactions can be written as Feynman Particle interactions can be written as Feynman diagramsdiagrams
Know the basic vertices, and conservation laws to see whether or not a reaction will occur.
Searching for a Grand Unified Searching for a Grand Unified TheoryTheory
Electroweak theory well established in SMElectroweak theory well established in SM Electromagnetic and weak forces are part of same theory Unify at high energy
?? Unifies with strong force also at high energy ???? Unifies with strong force also at high energy ?? …………then maybe eventually combine gravity also……then maybe eventually combine gravity also……
Particle Physics GlossaryParticle Physics Glossary
Fermion: ½ integer spin particle
Quarks: fundamental fermions which come in six types up,down,strange,charm,top,bottom
have fractional electrical charge and colour charge
Leptons: fundamental fermions which come in six types electron, muon,tau (all with electric charge) and electron neutrino, muon neutrino, tau neutrino (all neutral)
Generations: quarks and leptons come in three generations. Each generation looks like the previous but heavier.
Boson: integer spin particle. The fundamental bosons are the force carrier particles.
Electromagnetic force: carried by photon, interacts with electrically charged particles
Strong Force: carried by gluon, interacts with colour charged particles – the quarks. Joins quarks into hadrons
Weak Force: carried by Z0,W+,W-, responsible for nuclear Beta decay
ElectroWeak Theory: Electromagnetic and Weak Forces are explained by one combined theory.
Hadron: composite particle made of quarks
Meson: type of hadron containing 2 quarks (or more precisely one quark, one anti-quark)
Pions: the most common mesons (Kaons are most common meson with s quark)
Baryon: type of hadron containing 3 quarks
Proton,neutron: the most common baryons
Anti-matter: particles have anti-matter equivalents with same mass,opposite charge these behave identically.
Standard Model: very precisely tested theory of particle physics, containing electroweak and strong forces and fundamental particles.
The Big BangThe Big Bang
Evidence for the Big BangEvidence for the Big Bang It is dark at night! See Olbers Paradox Universe expanding Cosmic microwave background Relative abundance of elements in universe
The evolution of the universeThe evolution of the universe Stages in the formation of the universe
Big Crunch ? http://lhcb.web.cern.ch/lhcb/Big Crunch ? http://lhcb.web.cern.ch/lhcb/
Looking at larger scales Looking at larger scales
ManMan 1 m1 m Planet EarthPlanet Earth 101077 m m Solar System Solar System 10101313 m m1 light-day1 light-day Star separationStar separation 10101717 m m10 light-years10 light-years Galaxy sizeGalaxy size 10102121 m m100,000 light-years100,000 light-years Galaxy separation Galaxy separation 5 million light-years5 million light-years
in a cluster of Galaxies in a cluster of Galaxies 50 million light-years50 million light-years Large Scale StructureLarge Scale Structure 1 billion light-years1 billion light-years
Walls, voids etc.. in distribution of galaxiesSolar system seen from the outside!
Voyager 1
1977…
Picture, 1990
The expanding UniverseThe expanding Universe
Light from other galaxies is red-shiftedLight from other galaxies is red-shifted Doppler shift Edwin Hubble (1929)
Whole universe is uniformly expandingWhole universe is uniformly expanding There is There is no centreno centre to the universe to the universe
Hubble’s law:Hubble’s law:
v = H x d,
Velocity Hubble const. distance
H ~ 20 km/s/million light yrs
Expansion of space, not in space
Age of UniverseAge of Universe
Extrapolate back with Hubble’s lawExtrapolate back with Hubble’s law
Hence universe came into existence with very Hence universe came into existence with very high density, expanded out from therehigh density, expanded out from there
Particle and Nuclear physics determined the early Particle and Nuclear physics determined the early stages of evolution of the universestages of evolution of the universe
yrsHv
dt 10105.1
1
Olber’s “Paradox”: Why is the sky dark Olber’s “Paradox”: Why is the sky dark at night ?at night ?
If the observable universe isIf the observable universe is1. Static (eternal)
2. Infinite
3. Approximately uniformly filled with stars
Then sky should be Then sky should be as bright as the surface of a staras bright as the surface of a star
A faraway star looks dimmer, but there are more stars further away!
Brightness falls off as 1/r2
But area at distance r in some angular region, rises as r2
Hence, these cancel and sky should be equally bright as sun.
(e.g. Snowy mountains on a sunny day, equally bright in all directions irrespective of distance)
Resolving Olbers “Paradox”Resolving Olbers “Paradox”
The universe is not infinitely oldThe universe is not infinitely old Approx 15 billion years
The speed of light is finiteThe speed of light is finite We can only see part of the universe
Sky is dark at night because
1. Universe is young – distant light hasn’t reached us yet
and also
2. Expansion causes doppler shift (red-shift) of light
So,Big Bang solves Paradox
Stages in the evolution of the UniverseStages in the evolution of the Universe1.1. Planck EraPlanck Era
2.2. GUT EraGUT Era
3.3. Electroweak EraElectroweak Era
4.4. Particle EraParticle Era
5.5. Era of Nucleosynthesis Era of Nucleosynthesis 6.6. Era of NucleiEra of Nuclei7.7. Era of AtomsEra of Atoms8.8. Era of Galaxies – Now!Era of Galaxies – Now!
Book:
“The first three minutes”, by Steven Weinberg
(1) Planck Era: up to 10(1) Planck Era: up to 10-43-43 seconds seconds
Mysterious !Mysterious ! Universe begins at very high temperatureUniverse begins at very high temperature Maybe gravity unified with the other forces ?Maybe gravity unified with the other forces ? General Relativity and Quantum mechanics have General Relativity and Quantum mechanics have
never been successfully combined.never been successfully combined. We need a theory of Quantum GravityWe need a theory of Quantum Gravity
Characteristic Planck Time and Planck Length
Highly Speculative theories include M-theory particles are excitations on high dimensional
membranes. This has taken over from(and includes) String Theory, where particles are different vibrations of one type of string.
open string
closed string
(2) The GUT Era: up to 10(2) The GUT Era: up to 10-35-35 seconds seconds
We still don’t know a great deal but have some We still don’t know a great deal but have some better ideas !better ideas !
Universe full of fundamental particles, antiparticles, Universe full of fundamental particles, antiparticles, photons, gluons…everything!photons, gluons…everything!
No composite particles
Maybe the electroweak and strong forces (separate Maybe the electroweak and strong forces (separate in Standard Model) become united ? (in Standard Model) become united ? (GUTGUT))
Particle physics experiments give some support for converging coupling constants
InflationInflation: a short period of rapid expansion in the : a short period of rapid expansion in the universe. universe.
Universe starts as a rapidly expanding quantum bubble Analysis of cosmic background radiation of universe gives some
support for this model
((3) The Electroweak Era: up to 103) The Electroweak Era: up to 10-10-10 seconds seconds
Universe cooling, but still very hot, 10Universe cooling, but still very hot, 102828KK Again, no composite particles yet.Again, no composite particles yet. Three forces in the universeThree forces in the universe
Gravity Strong Electroweak
Electromagnetism and weak force are unified in Electromagnetism and weak force are unified in ElectroweakElectroweak
W+,W-,Z are massless, like the photons and gluons
(4) The Particle Era: up to 10(4) The Particle Era: up to 10-3-3 seconds seconds Temperature now dropped to ~10Temperature now dropped to ~101212KK Contains almost equal amount of particles and Contains almost equal amount of particles and
anti-particlesanti-particles And photons, gluons…
ElectroweakElectroweak Force splits into Force splits into ElectromagnetismElectromagnetism and and WeakWeak Interaction. Interaction.
W+,W-,Z become heavy, get the Higgs boson (not found yet)
As we cool further…As we cool further… Confinement starts:Confinement starts:
Quarks, anti-quarks,gluons combine to form protons and neutrons
Antimatter disappearsAntimatter disappears Matter/anti-matter cancel out. Small excess of matter ? Why ?
Particle physics experiments are investigating
eeeedduu ,,,,,,,
(5) Era of Nucleosythensis: (5) Era of Nucleosythensis: 0.001seconds to 3 minutes0.001seconds to 3 minutes
Temperature 10Temperature 101212 to 10 to 1099 K K The first composite particles, the protons and The first composite particles, the protons and
neutrons combine to form light nuclei:neutrons combine to form light nuclei: At the End:At the End:
75% (by mass) Hydrogen nuclei p,pn,pnn 25% (by mass) Helium nuclei ppn,ppnn ~0% Lithium
Nuclei onlyNuclei only, energy too high to bind electrons , energy too high to bind electrons into atomsinto atoms
The other nuclei come from Stars The other nuclei come from Stars muchmuch later later
75/25 % as measured, good evidence for big bang
No stable nuclei with 5 particles, so very few nuclei above He formed
(6) The Era of Nuclei:(6) The Era of Nuclei:3 minutes to 300,000 years3 minutes to 300,000 years
Universe is as hot as centre of sun (10Universe is as hot as centre of sun (1077K)K)
PlasmaPlasma of light nuclei and electrons and photons of light nuclei and electrons and photons
(7) Era of Atoms:(7) Era of Atoms:300,000 to 1 billion years300,000 to 1 billion years
Universe cools so atoms can be formed (3000K)Universe cools so atoms can be formed (3000K) Electrons captured by nucleiElectrons captured by nuclei
Universe is transparent – photons can fly around freely !Universe is transparent – photons can fly around freely ! No longer electrons that interact with them
This is how the This is how the microwave backgroundmicrowave background was created was created Most impressive evidence for big bang Universe was once very hot!
Cosmic Microwave BackgroundCosmic Microwave Background
Photons from when atoms formedPhotons from when atoms formed Universe continued to expand and coolUniverse continued to expand and cool Expect remnant radiation with 2.7K blackbody Expect remnant radiation with 2.7K blackbody
spectrum with isotropic spectrumspectrum with isotropic spectrum Discovered Penzias,Wilson 1965
COBE satellite, 1990
BUT not completely uniform at 10-5 K scale
COBE was first to see anisotropy, small fluctuations in temperature.
Latest results WMAP Feb. 2003
Compatible with inflation model
(8) Era of Galaxies:(8) Era of Galaxies:1 billion to 15 billion years (NOW)1 billion to 15 billion years (NOW)
Gravity plays its roleGravity plays its role Neutral H and He gas attractedNeutral H and He gas attracted
Small density variations are amplified Form gas cloudsForm gas clouds …….And eventually stars .And eventually stars
Thermonuclear reactions in stars form heavier Thermonuclear reactions in stars form heavier atomsatoms
Helium nuclei fusion e.g. 12C is lower energy state than 3 x 4He Get nuclei up to Iron Iron is most stable nuclei (binding energy per nuclei)
Higher nuclei require additional energy input Provided in supernova explosions
So, earth is supernova debris
(but measurements on galaxy rotation show particle physics does not give enough matter! Dark matter ?)
The Future of the Universe ?The Future of the Universe ?
Gravity fights the acceleration of the universeGravity fights the acceleration of the universe Expansion of universe could slow,stop, and then Expansion of universe could slow,stop, and then
contract.contract. Big Crunch?Big Crunch?
Amount of visible matter is not enough But strong evidence for additional dark matter But still not enough!
Could expand forever, but expansion slower and Could expand forever, but expansion slower and slower…slower…
And if there is a cosmological constant…And if there is a cosmological constant… An extra term that can give dark energy with negative pressure Expansion of universe may be accelerating!
““I’d like to thank the Swedish I’d like to thank the Swedish Academy”: five ways Academy”: five ways youyou can can
win a Nobel prize!win a Nobel prize!
1.1. Why is there more matter than anti-matter in the Why is there more matter than anti-matter in the universe ?universe ?
2.2. Find the Higgs Boson.Find the Higgs Boson.
3.3. Is there a Cosmological constant ?Is there a Cosmological constant ?
4.4. What is dark matter ?What is dark matter ?
5.5. Develop a Theory Of Everything !Develop a Theory Of Everything !