Summer Talk
Transcript of Summer Talk
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What is the Universe Made Of?
byBob Orr
Wanted to talk about the ATLAS experimentat a new large particle accelerator.
WHY?
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Plan of Talk
What we think visible matter is made of.
The Standard Model
Quantum forces
Gauge Theories & Unification of Forces
Cosmological Evidence for invisible matter
Supersymmetry
Large Hadron Collider
ATLAS
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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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Real & Virtual Particles
Interactions ofReal particles, conserve
Energy and Momentum.
Interactions ofVirtual particles, need not
conserve these, forshort times and
distances.
Hiesenbergs Uncertainty Principle
E t
p x
=
=
Energy & time
Momentum & position
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Real & Virtual Particles
Interactions ofReal particles, conserve
Energy and Momentum.
Interactions ofVirtual particles, need not
conserve these, forshort times and
distances.
Hiesenbergs Uncertainty Principle
E t
p x
=
=
Energy & time
Momentum & position
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Weak Interaction
A force very like electromagnetism; but
acts on Weak Charge
W Z 0
In Fact, electromagnetism and weak force
are aspects ofunified electroweak force
Electric charge and weak charge are
related
Three force carriers W Z 0
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Electroweak Force
Photon is massless
are very massive
Almost 100 times proton mass
W Z 0
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3 Generations
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3 Generations
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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 fundamental
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
electromagnetism
weak force
strong (colour) force
become aspects ofGrand Unified Force
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Understand History of Universe?
What we think (thought?) visible matter is
made of.
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Hubbles Law & Big Bang.
Big Bang model came from observation tha
Universe is expanding
For distant galaxies
velocity = x distance
is Hubble Parameter
Whether Universe continues to expand, or
starts to contract depends on density of
matter and energy in Universe.
0
0
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Fate of Universe
If , the density of matter and energy is
greater that a critical density theuniverse 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
c
0
c
0 0 0
028 3
= =
cG
H
0 1>
0 1=
0 1
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Measuring 0
Amazingly enough can measure
total matter/energy density in universe
Measure temperature fluctuations in
remnant of fireball from Big Bang.
0 1
=
Map of sky temp
3 Kelvin
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Measuring 0
Amazingly enough can measure
total matter/energy density in universe
Measure temperature fluctuations in
remnant of fireball from Big Bang.
0 1
=
Map of sky temp
3 Kelvin
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Measuring 0
Amazingly enough can measure
total matter/energy density in universe
Measure temperature fluctuations in
remnant of fireball from Big Bang.
0 1
=
Map of sky
temp3 Kelvin
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Density of Standard Model Matter
Referred to as Baryonic Matter
Density is
If Universe is made of quarks & leptons
measured from abundance of elements
produced in nucleosynthesis of Big Bang.
Deuterium, Helium, Lithium
Most of Universe is not Standard Model
matter. Some kind ofDark Matter
B = =0 1
B
= 0 05.
B 0
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Density of All Matter
Can measure density of all matter, whatever
its nature, , by looking at gravitationalmotion:
rotation curves of galaxies
motion of galactic clusters
There is indeed Dark Matter
So even with this Dark Matter, cannot
account for
Universe must be 60% Dark Energy
= 0 0 1.4 .
0
1=
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Dark Energy
If the expansion of the Universe is being
slowed down by gravitational attraction;expect that in remote past galaxies were
moving apart more rapidly than now.
Observations ofdistant supernovae show
that in the past galaxies were moving apartmore slowly
Expansion is accelerating
Driven by some quantum field permeating
the Universe.
= 0 85 0 2. .
( .4 . ) ( . . ) . .0 0 1 0 85 0 2 1 25 0 22 + =
+ = 1
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Calan/Tololo(Hamuy et al, A.J. 1996)
SupernovaCosmologyProject
(0.5,0.5) (0
( 1, 0 ) (1(1.5,0.5) (2
(,) =
( 0, 1 )
Flat
redshift z
14
16
18
20
22
24
26
0.02 0.05 0.1 0.2 0.5 1.00.02 0.05 0.1 0.2 0.5 1.0
Supernova Cosmology Project
Perlmutter et al. (1998)
astro-ph/9812133
In flat universe: M = 0.28 [ 0.085 statistical] [ 0.05 systematic]
Prob. of fit to = 0 universe: 1%
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1 2 0 1 2 3
-1
0
1
2
3
2
3
Supernova Cosmology Project
Perlmutter et al. (1998)
Best fit age of universe: to = 14.5 1 (0.63/h) Gyr
Best fit in flat universe: to = 14.9 1 (0.63/h) Gyr
19 Gyr
14.3 Gyr
accele
rating
decele
rating
11.9 Gyr
9.5 Gyr
7.6 Gyr
H0t063 km s-1 Mpc-1
=
wwwsupernova.LBL.gov
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Need for Supersymmetry
In Grand Unified Theories cannot Unify
forces, unless postulate unseen form ofmatter
Higgs mass runs away to Plank Scale
Three forces never have same strength
Unless all particles have supersymmetric
particle partners (of higher mass)
+Sleptons Bosinos
Squarks
Spin 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 with
normal matter
Lightest SUSY particle good candidate for
Dark Matter(Caveat - Recent evidence indicates that
Dark Matter is Self-Interacting)
Hope to produce
(SUSY - antiSUSY ) pairs and Higgs
at
Large Hadron Collider
Susy Normal Susy +
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How to Make Matter / AntiMatter?
Colliding high energy beams
Energy of beams transformed into mass
of new particles
LHC will be proton - proton collider
For SUSY observation must contain ALL
visible energy, in order to infer invisible SUSY
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Superconducting Magnet
8 Tesla
In order to accelerate protons to high energy,
must bend them in circular accelerator
7 TeV momentum needs intense magnetic field
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LHC Magnet
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LHC Tunnel
This is an arc of the circular tunnel
Circumference 26.7 Km
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CERN Seen from the Air
Tunnels of CERN accelerator complex
superimposed on a map of Geneva.
Accelerator is 50 m underground
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CERN Seen from the Air
Tunnels of CERN accelerator complex
superimposed on a map of Geneva.
Accelerator is 50 m underground
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Generic Experiment
Layers of detector systems around collision poin
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Particle Detection
Different particles detected by differenttechniques.
Calorimeterdetects ionisation from a
showerof secondaries produced by
primary particle.
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Generic Detector
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ATLAS
Our Detector
Canada is building
Endcap Calorimeters (TRIUMF
Alberta, UVic)
Forward Calorimeters (Toronto
Carleton)
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Forward Calorimeter
FCAL1 - Cu matrix + rods
2.6FCAL2/3 -W matrix, W rod
Cu skeleton
3.5/3.4
Side view of FCAL
Cryostat
FCAL is mainly tungsten, uses liquid argon
as detecting medium for ionisation from showe
Close to colliding beams - intense radiation
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O R R P I N 1 5 3 3 1 3 1
Spacer x 5
F i g u r e 8 : A n e x p l o d e d v i e w s h o w i n g h o wt h e c a l o r i m e t e r i s m a d e u p o f t u b u l a r e l e c t r o d e s
e m b e d d e d i n a m a t r i x o f s m a l l s i n t e r e d t u n g s t e n s l u g s .
T h eF C A L s i g n a l i s g e n e r a t e d b y i o n i z a t i o n i n t h e L i q u i d A r g o n l l e d g a p b e t w e e n
t h e r o d s a n d t h e t u b e s . T h e s i g n a l s a r e r e a d o u t v i a p i n s t t e d i n t o h o l e s a t o n e e n d o f
t h e r o d s . T h e s i g n a l s f r o m 6 ( 8 ) t u b e s a r e s u m m e d o n k a p t o n b o a r d s a t t h e e n d o f t h e
F C A L 2 ( F C A L 3 ) mo d u l e .
( b . 1 ) E n d p l a t e s
T h ee n d p l a t e s a r e c o n c e p t u a l l y s i m p l e c o n s i s t i n g o f c o p p e r p l a t e s a p p r o x i m a t e l y 1 "
t h i c k w i t h h o l e s f o r t h e t u b e s . I n p r a c t i c e , a c h i e v i n g t h e r e q u i r e d t o l e r a n c e s i n p l a t e
a t n e s s a n d t h e d e t a i l s o f t h e i n t e r n a l g r o o v e h a s p r o v e d t o b e a c h a l l e n g e . O f t h e 6
c o m p a n i e s t h a t w e r e s o l i c i t e d f o r b i d s o n l y t h e S T C a t C a r l e t o n s u b m i t t e d a q u o t a t i o n .
O n eo f t h e d i c u l t i e s w i t h t h e j o b i s t h e t e n d e n c y o f c o p p e r t o d i s t o r t d u r i n g m a c h i n i n g
d u e t o r e s i d u a l s t r e s s e s i n t h e m a t e r i a l . F o r t h i s r e a s o n w e h a v e c h o s e n f u l l y a n n e a l e d
c o p p e r a n d a r e m o n i t o r i n g t h e a t n e s s o f t h e p l a t e s d u r i n g t h e m a c h i n i n g o p e r a t i o n s .
( b . 2 ) T u b e s , R o d s a n d S p a c e r s
T h ec o p p e r t u b e s a r e u s u a l l y s p e c i e d b y e x t e r n a l d i a m e t e r a n d w a l l t h i c k n e s s . F o r
t h e F C A L t h e k e y d i m e n s i o n i s t h e i n t e r n a l d i a m e t e r wh i c h f o r m s o n e b o u n d a r y o f t h e
i o n i z a t i o n g a p . E x p e r i e n c e w i t h t h e m a q u e t t e h a s s h o w n t h a t i n d u s t r y c a n p r o d u c e t u b e s
t h a t m e e t o u r s p e c i c a t i o n s .
Hadronic Forward Calorimeter
Principle
W(97%),
Ni(2.1%),
Fe(0.9%)
Tungsten rods
in copper
tubes in a
matrix built
of tungstenslugs
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FCAL2 Module 0
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FCAL2 Module 0
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FCAL2 Module 0
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Preliminary Results
Visible energy distribution for 200 GeV pions
- both modules
- tail catcher energy cut
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Preliminary Results
Beam Energy [GeV]
RelativeEnergyResolution
[%]
0
5
10
15
20
25
30
35
40
0 25 50 75 100 125 150 175 200
ATLAS Requirement (jets)
Test Beam Data
&
Fit
MC of Test Beam
MC Intrinsic Resolution.
Pion Energy Resolution cfMonte Carlo
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Higgs Discovery
End on View of a simulated Higgs Boson
produced in the ATLAS Detector