Download Dissecting the Higgs Discovery: The Anatomy of a 21st Century

Dissecting the Higgs Discovery:
The Anatomy of a 21st Century Scientific
Achievement
Lauren Tompkins
Arthur H. Compton Lectures
October 12th, 2013
Lecture 2
Accelerators: Creating new
particles out of (very) thin air
Nobel Prize!
• Higgs and Englert won
•
the Nobel prize for
developing a theory of
how particles acquire
mass
The prize was awarded
this year because Atlas
and CMS amassed enough
evidence to say that the
newly discovered particle
is a Higgs boson
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Schedule of Lectures
[10/5] Welcome to the Theater: Introduction to the Standard Model and
Higgs Boson
[10/12] Accelerators: Creating particles out of (very) thin
air
[10/19] Seeing the Higgs with light
[10/26] Guest Lecture: Martin Bauer On Theory
[11/2] Seeing the Higgs with heavy particles
[11/9] Digesting the Data: Triggering, Data Processing
[11/16] Finding the Needle in the Haystack: Data Analysis and Statistics
[11/23] What else have we learned from the LHC?
[11/30] No Lecture for Thanksgiving
[12/7] No Lecture for Physics with a Bang
[12/14] What's next for the LHC?
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Outline
• Brief Review of Last Week
• Introduction to Accelerators
• Why we use accelerators
• LHC Overview
4
Last Week
5
Last Week
•
Standard Model describes the
fundamental particles and forces
•
3 forces: Strong, Electromagnetic and
Weak nuclear
•
6 quarks and 6 leptons
5
Last Week
•
•
Standard Model describes the
fundamental particles and forces
•
3 forces: Strong, Electromagnetic and
Weak nuclear
•
6 quarks and 6 leptons
The Higgs field exists everywhere,
all of the time and a particle’s
mass is determined by how
strongly it interacts with the
electron
field
•
The Higgs boson is the physical
manifestation of the field
x
x
neutrino
top
quark
x
xx x
x
x
x = interaction with Higgs field
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Loose Strings
Comparison to EM
Note: In this plot the Y axis is defined such that the energy of the field = 0 at 0
field strength. Energy is always defined relative to some reference point.*
*note, this is not strictly true for General Relativity. See this for a discussion
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Outline
• Brief Review of Last Week
• Introduction to Accelerators
• Why we use accelerators
• LHC Overview
7
Accelerators 101
Rhodatron, commercial accelerator
•
An accelerator is a device which
increases the energy of a particle by
increasing its speed
•
Accelerators are used to accelerate:
•
•
electrons, protons and ions
Used for a wide variety of applications:
•
•
•
•
Cancer therapy
•
“Frontier” physics
Ion implantation for electronics
LHC
Polymer cross-linking in plastics
Biology, chemistry, materials science
research
More info: http://science.energy.gov/~/media/hep/pdf/files/pdfs/accel_for_americas_future_final_report.pdf
8
How acceleration happens
• To accelerate an object you need to exert a force
on it (F = ma) :
•
•
Electromagnetic force is the only viable option!
Can accelerate only charged particles
• Electric fields push particles in the direction of the
field
•
Constant field = constant acceleration
• Hard to maintain large constant field, so alternating
fields are used
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Accelerating Particles
10
Accelerating Particles
11
Linear Accelerator
acceleration regions
12
The trouble with linear
accelerators
• To achieve high energies, linacs
need to be very long
•
Highest energy one was 2
miles long! (Stanford)
• Need to go to circular designs
to make compact machines
The SLAC linear accelerator
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Magnetic Fields
• To have a circular accelerator
•
you need to bend charge
particles
Magnetic fields push charged
particles perpendicular to
their direction
•
In a constant magnetic field,
charged particles travel in a
circular orbit
14
Cyclotron
• E.O. Lawrence first combined electric and magnetic
fields to produce cyclotron
•
Nobel Prize 1939
15
Animated Cyclotron
16
Modern Circular Accelerators
• Modern accelerators use varying magnetic field
strength to bend particles and timed radio
frequency to accelerate them in at a fixed radius
Acceleration region
Magnets
Vacuum tube
Synchrotron
Straight Sections
Injector
Electromagnets
Acceleration region (RF cavities)
17
Outline
• Brief Review of Last Week
• Introduction to Accelerators
• Why we use accelerators
• LHC Overview
18
Why accelerate particles?
19
Why accelerate particles?
• (Obvious) Answer: to make higher
energy particles!
19
Why accelerate particles?
• (Obvious) Answer: to make higher
energy particles!
• Why do we want higher
energy particles?
19
Why accelerate particles?
• (Obvious) Answer: to make higher
energy particles!
• Why do we want higher
energy particles?
•
Particle physicist answer: E = mc2
19
Why accelerate particles?
• (Obvious) Answer: to make higher
energy particles!
• Why do we want higher
energy particles?
•
Particle physicist answer: E = mc2
• The real equation:
19
Why accelerate particles?
• (Obvious) Answer: to make higher
energy particles!
• Why do we want higher
energy particles?
•
Particle physicist answer: E = mc2
•
E2 = m2c4 + p2c4
• The real equation:
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Why accelerate particles?
• (Obvious) Answer: to make higher
energy particles!
• Why do we want higher
energy particles?
•
Particle physicist answer: E = mc2
•
•
E2 = m2c4 + p2c4
• The real equation:
A particle’s momentum can be
converted into mass
19
Why accelerate particles?
• (Obvious) Answer: to make higher
energy particles!
• Why do we want higher
energy particles?
•
Particle physicist answer: E = mc2
•
•
E2 = m2c4 + p2c4
• The real equation:
A particle’s momentum can be
converted into mass
19
Matter out of Energy!
20
Relativity!
• The closer a
•
particle gets to
the speed of
light, it’s total
energy
dramatically
increases!
We win a lot by
small increases
in velocity!
Relativistic energy
Classical energy (wrong)
http://www.phys.unsw.edu.au/einsteinlight/jw/module5_equations.htm
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So, we accelerate particles to give them more energy
and from energy, we can create new particles, like
the Higgs!
22
23
Outline
• Brief Review of Last Week
• Introduction to Accelerators
• Why we use accelerators
• LHC Overview
24
The LHC
• Located near Geneva, Switzerland
• Pan-european project with significant North
American and Asian contributions
25
• Tunnel is 27 km long, ~100m below the earth.
• Collides protons at a center of mass energy of 14 TeV!
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Specs
27
• 9600 magnets
Specs
27
• 9600 magnets
•
Specs
Bending magnets: 1232 dipoles (most of the total magnet
mass)
27
• 9600 magnets
Specs
•
Bending magnets: 1232 dipoles (most of the total magnet
mass)
•
Focussing and correcting magnets make up the rest
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• 9600 magnets
Specs
•
Bending magnets: 1232 dipoles (most of the total magnet
mass)
•
•
Focussing and correcting magnets make up the rest
Cooled to 1.7 degrees above absolute 0 using superfluid
helium
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• 9600 magnets
Specs
•
Bending magnets: 1232 dipoles (most of the total magnet
mass)
•
•
Focussing and correcting magnets make up the rest
Cooled to 1.7 degrees above absolute 0 using superfluid
helium
• 8 RF cavities per beam
27
• 9600 magnets
Specs
•
Bending magnets: 1232 dipoles (most of the total magnet
mass)
•
•
Focussing and correcting magnets make up the rest
Cooled to 1.7 degrees above absolute 0 using superfluid
helium
• 8 RF cavities per beam
•
2 Million V @ 400 MHz
27
• 9600 magnets
Specs
•
Bending magnets: 1232 dipoles (most of the total magnet
mass)
•
•
Focussing and correcting magnets make up the rest
Cooled to 1.7 degrees above absolute 0 using superfluid
helium
• 8 RF cavities per beam
•
•
2 Million V @ 400 MHz
Wall plug: 120V @ 60Hz
27
• 9600 magnets
Specs
•
Bending magnets: 1232 dipoles (most of the total magnet
mass)
•
•
Focussing and correcting magnets make up the rest
Cooled to 1.7 degrees above absolute 0 using superfluid
helium
• 8 RF cavities per beam
•
•
2 Million V @ 400 MHz
Wall plug: 120V @ 60Hz
• All in a vacuum system
27
• 9600 magnets
Specs
•
Bending magnets: 1232 dipoles (most of the total magnet
mass)
•
•
Focussing and correcting magnets make up the rest
Cooled to 1.7 degrees above absolute 0 using superfluid
helium
• 8 RF cavities per beam
•
•
2 Million V @ 400 MHz
•
Beam vacuum is 10-13 of earth’s atmosphere!
Wall plug: 120V @ 60Hz
• All in a vacuum system
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Dipoles
• 35 tonnes each
• 14.3 m long
• 8.3 Tesla field
•
•
Earth’s field: 5x10-5 T
•
Medical MRI machines:
1.5-3T
Refrigerator magnet:
1x10-3 T
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Magnetic field of LHC dipoles
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From the inside
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Why so cold?
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Why so cold?
• To generate high magnetic field you need high
electric current
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Why so cold?
• To generate high magnetic field you need high
electric current
• Currents produce magnetic fields
31
Why so cold?
• To generate high magnetic field you need high
electric current
• Currents produce magnetic fields
• In normal metals, high current = high resistance
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Why so cold?
• To generate high magnetic field you need high
electric current
• Currents produce magnetic fields
• In normal metals, high current = high resistance
•
Very hot! Needs lots of power
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Why so cold?
• To generate high magnetic field you need high
electric current
• Currents produce magnetic fields
• In normal metals, high current = high resistance
•
Very hot! Needs lots of power
• Enter superconductivity!
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Why so cold?
• To generate high magnetic field you need high
electric current
• Currents produce magnetic fields
• In normal metals, high current = high resistance
•
Very hot! Needs lots of power
•
At very low temperatures, some metals loose all
resistance
• Enter superconductivity!
31
Why so cold?
• To generate high magnetic field you need high
electric current
• Currents produce magnetic fields
• In normal metals, high current = high resistance
•
Very hot! Needs lots of power
•
At very low temperatures, some metals loose all
resistance
•
Can have (in theory) infinite current!
• Enter superconductivity!
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Picture of Superconductivity
http://www.abc.net.au/science/articles/2011/07/20/3273635.htm
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The accident....
•
19 Sep 2008 damaged
~50 magnets
•
Delayed start until late
2009!
33
November 2009: First
Collisions!
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•
The LHC is the 5th
accelerator in the a
chain
•
Start with a bottle of
hydrogen
•
First use a linear
accelerator
•
Followed by 3 small(ish!) circular
accelerators to get protons to 450 x
rest energy
•
LHC take protons from 450x rest
energy to 7000x rest energy
•
~3000 bunches of 1011 protons at once
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