summer talk

7/29/2019 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





0 1

=

Map of sky temp

3 Kelvin


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Measuring 0





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

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