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Transcript of Thomas Lohse Humboldt-Universität zu Berlin Thomas Lohse Humboldt-Universität zu Berlin Stuff and...
Thomas Lohse
Humboldt-Universität zu Berlin
Thomas Lohse
Humboldt-Universität zu Berlin
Stuff and GlueParticles and Forces
• Experimental methods
• What is matter?
• Which forces stabilize matter?
• Open questions and the next steps
Greek Philosophy• Empedokles (500-430 B.C.)
– four elements: fire, water, earth, air– two fources: love , hatred mixing, separating
• Platon (427-347 B.C.)– symmetric shapes: beauty of laws of nature
• Demokrit (460-371 B.C.)– atoms: different forms and weights
– emptiness: binding and motion in the void
fire water earth air
How to resolve structures?
eye: ~1 mm resolution
scattering of photons:
lense: ~ 0.1 mm resolution
light microscope: ~ 1 µm
Limited by photon
How to resolve structures?
particle scattering:
Rutherford scattering:
E = O(MeV) α-particles
λ = O(fm) gold atoms with nuclei
ph
modern particle accelerators, e.g.
HERA: e(27 GeV) on p(920 GeV)
resolution 0.001 fm
TV tube
a) linear accelerators
Fermilab injector
the principle
superconducting RF cavity for future linear
collider TESLASLAC linac first linear collider
Particle Accelerators
Two Topologies
Colliding beams (e+e–, ep, pp...)
Myon Chambers
Hadron Calorimeter
Tracking ChamberElectromagn. Calo.
e–
cylindrical shell structureof subdetectors
cylindrical shell structureof subdetectors
Two Topologies
Fixed target (μ–A, pA, ...) Forward layerstructure of subdetectors
Forward layerstructure of subdetectors
HERA-B
21 m
Si-vertex detectorSi-vertex detector tracking systemtracking system
magnet
RICH detectorRICH detector EM calorimeterEM calorimeter
hadron absorber& muon system
hadron absorber& muon system
Subdetector Tasks
40 cm
Silicon Microstrip Wafers => vertex tracking
typical impact parameters O(100 μm)
Proportional Drift Chambers => main tracking
typical coordinate resolution O(200 μm)
magnetic field => particle momentum from curvature
Subdetector Tasks
HERA-B RICH
Particle Identification: example Ring Imaging CHerenkov detectors
Ring radius => p/m => π,K,p sep.
charged particle in radiator gas
mirror
light detector (e.g. PM tubes)
Cherenkov cone
point on Cherenkov ring
Subdetector TasksCalorimeters (lead, steel, uranium...)
electromagnetic showers => e,γ energy
hadronic showers => energy of hadrons
penetrating particles => muons
Structure of MatterCrystal
Molecule
Nucleus
Atom
elements of normal matter:
quarks leptons
up
Q = +2/3
neutrino
Q = 0
down
Q = –1/3
electron
Q = –1
• neutrinos: from β-decay / sun burning
• quarks: always bound, ”confinement“
How to see the quarksaccelerators => high energy quarks
quarks => jets of secondary hadrons
jet
jet
e+ e–
quark
antiquark
How to measure quarks in the protonaccelerators => knock quarks out of protons
final state kinematics => initial quark momentum
jet
e
Quantitative: proton structure functions
quark densities in the protonas function of thequark momentum
and theresolution of the scattering
quark densities in the protonas function of thequark momentum
and theresolution of the scattering
Heavier short-lived Generations
very strange mass spectrum...
High energy collisions reveal heavier versions of quarks and leptons!
up ... charm ... top down ... strange ... bottom
electron ... muon ... tau νe ... νμ ... ντ
The Periodic System ofElementary Particles
u-quark group
d-quark group
neutrino group
electron group
quark/lepton periods
I II II
I
particle physics:periods = families
More Families???
LEP:
ll
qqZeevisible
invisible
ΓZ = Γvis + Γinvis
Γinvis = Nfam · Γν
measurements: Nfam = 3
lineshape of Z resonance from LEPlineshape of Z resonance from LEP
The Fundamental Forces
force quanta mass range
gravity graviton(?) 0
electromagneticphoton 0
weakW± , Z 80, 90GeV ~.001 fm
stronggluons 0 O(1) fm
N
S
q q pp
nn
nnp
ppp
p
n
nnp
pnpnp
Xvpv
vepn e
(confinement)
Supersymmetry: still a hypothesis...
Matter Particles
Spin 1/2
Superpartners of Matter Particles
Spin 0
Why is the Weak Force Weak?
ep cross section vs. squared momentum transfer
electromagnetic
weak
unification at22WMQ
γ
W
e
νIt isn‘t weak at all!!!
It is just a mass effect!!!
It isn‘t weak at all!!!It is just a mass effect!!!
A Unified Single Force?
We have just seen this:Electroweak unification
E = 100 GeV like 10-10s after big bang
Grand electroweak/strong unificationE = 1014 GeV like 10-35s after big bang Planck Scale: unification with gravity
E = 1019 GeV like 10-43s after big bang
kTE
Why such funny asymmetric masses of force particles?
Hypothesis: There is a background field in the
universe... the Higgs field
Vacuum field strength
Symmetric potential energy
Initial state of the universeInitial state of the universe
Inflation: spontaneoussymmetry breaking
Inflation: spontaneoussymmetry breaking
Asymmetric ground state:• masses are created• a Higgs particle appears
Asymmetric ground state:• masses are created• a Higgs particle appears
A conference banquet... The nobel prize winner enters the room...
The physicists next to him turn immediately to talk to him. It becomes hard for him to move (accelerate). He is effectively massive...
physicists = background Higgs fieldnobel prize winner = massive particle
How does Mass Creation Work?
How does Mass Creation Work?
A conference banquet... A rumour is injected... The physicists cluster where the rumour spreads out. It gets hard for the rumour to move (accelerate)...rumour = Higgs particle
The Higgs particle is itself massive!
And Where is the Higgs?
direct search not yet successful:
mH > 114 GeV
Higgs mass enters via quantum corrections
in precision measurements
fit-2
• Why such a strange mass spectrum ?
• Does the Higgs particle exist ?
• Why three families ?
Open Questions
??
• Why symmetric lepton/quark structure ?
• Is there a unified force ?
• Supersymmetric partners of particles and fields ?
• Characteristic pattern of quark family transistions ?
• Transitions in lepton family ?
• Where/how is the antimatter gone ?
• What about gravity ? Extra space-time dimensions? ...
The next big steps: (1) LHC / CERN
ATLAS detector
LHC: 7 TeV protons on 7 TeV protonsStart of operation: 2007-2008
LHC: 7 TeV protons on 7 TeV protonsStart of operation: 2007-2008
LHC goals:• establish the Higgs particle• search for supersymmetry• search for new effects
LHC goals:• establish the Higgs particle• search for supersymmetry• search for new effects
accessible mass scale: ~1 TeV
The next big steps: (2) TESLA / DESY
• 33 km linear e+e–-collider, energy 500-800 GeV• Similar projects proposed by U.S.A. and Japan• start not before 2013
• 33 km linear e+e–-collider, energy 500-800 GeV• Similar projects proposed by U.S.A. and Japan• start not before 2013
TESLA goals:• detailed properties of Higgs particle• highest precision tests of electroweak force• detailed properties of supersymmetric particles• search for extra dimensions ...
TESLA goals:• detailed properties of Higgs particle• highest precision tests of electroweak force• detailed properties of supersymmetric particles• search for extra dimensions ...