The Large Hadron Collider LHC

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The Large Hadron Collider (LHC)

• Prof Steve Lloyd
• Queen Mary, University of London

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Outline

• The Standard Model
• Beyond the Standard Model
• The LHC
• Success!
• Failure!
• Outlook
• The Grid

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The History of the Universe
Particle Physics
Astronomy
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The Standard Model
The Standard Model of Particle Physics

• Everything is made up of 6 Quarks and Leptons
• They are arranged in 3 Generations of
  increasing mass
• Each particle has a similar anti-particle
  with opposite properties
• They interact via 4 force carrying particles
  the photon (?), gluon (g), Z and W
• There should be a Higgs Particle to give them
  all mass (except the photon)

Electro-magnetism
Strong Interaction
Weak Interaction
Matter
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The Four Forces
Strong Force Strength 1 Range
10-15m Exchange Gluon
Gravity Strength 6x10-39 Range
Infinite Exchange Graviton?
Electromagnetic Force Strength 1/137 Range
Infinite Exchange Photon
Weak Force Strength 10-6 Range
10-18m Exchange W Z0
Taken from http//universe-review.ca/F15-particle.
htm
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Unification of Forces
The strength of electromagnetism aEM increases
while that for the strong interaction aS
decreases with energy
Unification Point
Large distance - more force - quarks bound
Short distance - less force - quarks free
short distance high energy
large distance low energy
1015 GeV
The strengths come together at the so called
Unification point 1015 GeV ? one constant aGUT
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Unification of Forces
Electromagnetism
Weak Force
Gravity
Electroweak Force
Strong Force
Nuclear Forces
Grand Unification?
Theories of Everything?
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The Higgs Particle

• Primary objective of the LHC
• What is the origin of Mass?
• Is it the Higgs Particle?

Massless Particle Travels at the speed of light
Low Mass Particle Travels slower
High Mass Particle Travels slower still
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The Higgs Field
Symmetry broken
Symmetry
Massive modes W and Z
The energy is gt 0 when the field 0 (false
vacuum)
Massless modes photon
In vacuum with energy 0 the Higgs field is
non-zero ? Higgs particles

• Energy/Volume constant
• Energy increases
• Work Done
• Force outwards
• Pressure outside (0) gt inside
• Pressure inside negative

Real Vacuum
False Vacuum
Force
False Vacuum
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The Higgs Mass
The width (lifetime) of the Z0 depends slightly
on the Higgs mass log(mH)
Fit to existing data with Higgs mass as free
parameter
Excluded by direct searches at lower energies
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Beyond the Standard Model
Standard Model very successful (apart from lack
of Higgs so far)

• But doesnt explain or predict
• The masses of the particles
• The strengths of the forces
• Why 3 generations?
• Why 3 colours?
• Are Strong and Electroweak forces related?
• Why quarks and leptons have exactly related
  charges?
• Where is all the anti-matter?
• Gravity

Many very detailed measurements
Need to go Beyond the Standard Model
Standard Deviations
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Supersymmetry
Theorists predict that for every known particle
(quark, lepton etc) there is a heavier
supersymmetric partner (squark, slepton etc)
Every fermion has a supersymmetric boson partner
Every boson has a supersymmetric fermion partner
These have useful properties that help cancel out
infinities in the current Standard Model at high
energies and help include Gravity Superstring
Theory
The lightest supersymmetric particle is (usually)
stable ? Dark Matter Candidate
These supersymmetric particles should be created
at the LHC ? Large missing energy/momentum
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Supersymmetric Particles
The names of the partners are constructed by
putting an s in front of fermion names an ino
after boson names and a on top of symbol






Mix ? neutralino





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Mini Black Holes
In normal geometry minimum mass for a Black Hole
is Plank Scale Ep1019GeV - well beyond
conceivable accelerators
In (String) theories with (large) extra
dimensions Effective Plank Scale ED
(EP2V)1/(D-2) For dimensions D10 and volume Vfm
? EDTeV
If energy gt ED and impact parameter lt
corresponding Schwarzschild radius ? Mini Black
Hole
Lifetime very short ? evaporates in 10-26s
isotropically

• Safe because
• Decay before gravitationally attracted to
  anything else
• Would have been produced in cosmic rays already

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Particle Physics Progress
Theory
Electroweak Unification
LEP and SLC measure W Z precisely
Predicts W Z Particles
Discovery Experiments (Hadron - Hadron)
Precision Experiments (Lepton - Lepton)
CERN SPS discovers W Z
Detailed predictions of properties
Theory
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Particle Physics Progress
Theory
Standard Model beyond
New Linear Collider measures properties precisely
Predicts Higgs Particle
Discovery Experiments (Hadron - Hadron)
Precision Experiments (Lepton - Lepton)
CERN LHC discovers Higgs Supersymmetry
Detailed predictions of properties
Theory
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Lepton v Hadron Colliders

• Precision Machines
• (Lepton - Lepton)
• Fundamental particles collide
• Collision energy well known
• Clean
• Lower energy (limited by synchrotron radiation)

• Discovery Machines
• (Hadron - Hadron)
• Composite particles collide
• Collision energy unknown
• Dirty
• Higher energy

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CERN
European Organization for Nuclear Research Centre
European Researche Nucleare
http//www.cern.ch
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The LHC
The size was set by the existing 27km LEP tunnel
The magnetic bending field set by the most
powerful feasible superconducting dipole magnets
(8.4 T)
Sets the maximum proton energy at 7 TeV 14 TeV
total energy
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LHC Accelerator Complex
Protons accelerated in stages to 0.999999 speed
of light
1600 superconducting magnets each 27 tonnes
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Building the LHC
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The LHC
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The LHC Complex
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The LHC Detectors

• CMS
• General purpose purpose detect everything and
  anything

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The ATLAS Detector
Solenoid field 2.6 T Toroid field 4T 7000 Tonnes
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ATLAS
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The ATLAS Collaboration
37 countries 169 Institutes 2500 Authors
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Mr Big and Mr Heavy
6 Floors
5 4 3 2 1 0
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CMS
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Closure of the LHC
The Final Piece Closure of the LHC beam pipe
ring on 16thJune 2008 ATLAS was ready for data
taking in August 2008
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Cosmic Rays in ATLAS
X-ray of the ATLAS cavern with cosmic muons
Access shafts
Elevators
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LHC Start Up Day
LHC Control Room
ATLAS
10th September 2008
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Beam RF Capture
Mountain range plot
Each line one bunch orbit
Correct phasing Correct reference
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First Beam in ATLAS
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ATLAS as a
Bubble chamber
A cosmic event with field on
Occupancy 1
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Success!
2009
2009
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LHC incident on Sept 19th
Systems reacted as expected until here
Powering tests in Sect 3-4 for 5.5 TeV operation
Resistive zone in bus between C24 and Q24
In lt 1 sec power converter tripped and dump
started
Electrical arc in bus, punctured helium enclosure
Safety valves start venting helium to the tunnel
Pressure rise too fast for valves, pressure wave
in isolation vacuum
Damage to super-insulation for some magnets
Helium release into isolation vacuum of cryostat
Displacements where wave hits vacuum barriers
Both beam pipes cut open and contaminated
About 60 magnets to be removed for repairs etc
No more beam in 2008
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Magnet Movements
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Magnet Damage
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Magnet Damage
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Outlook

• Prevention of similar incidents
• Search for indicators of faulty connections in
  commissioning data
• Retests of all suspicious locations
• Improvements on Quench Protection Systems
• Mitigation of consequences in case of similar
  incidents
• Increase number and discharge capacity of relief
  valves
• Reinforce external anchoring of cryostats at the
  locations of the vacuum barriers

Current Schedule
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The LHC Data Challenge

• 100,000,000 electronic channels
• 800,000,000 proton-proton interactions per second
• 0.0002 Higgs per second
• 10 PBytes of data a year
• (10 Million GBytes 14 Million CDs)

Starting from this event
We are looking for this signature
Selectivity 1 in 1013 Like looking for 1
person in a thousand world populations Or for a
needle in 20 million haystacks!
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From Web to Grid
Building a massive distributed computer system
The Grid
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Electricity Grid

• Analogy with the Electricity Power Grid

Power Stations
Distribution Infrastructure
'Standard Interface'
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Computing Grid
Computing and Data Centres
Fibre Optics of the Internet
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The Grid
Your Program
Single PC
Grid
Your Program
PROGRAMS
MIDDLEWARE
User Interface Machine
Word/Excel
Games
Email/Web
Workload Management
Information Service
OPERATING SYSTEM
CPU
Replica Catalogue
Disks, CPU etc
Bookkeeping Service
Middleware is the Operating System of a
distributed computing system
CPU Cluster
CPU Cluster
CPU Cluster
Disk Server
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Getting Started
1. Get a digital certificate (UK Certificate
Authority)
Authentication who you are
2. Join a Virtual Organisation (VO) - atlas
Authorisation what you are allowed to do
3. Get access to a local User Interface Machine
(UI) and copy your files and certificate there
4. Write some Job Description Language (JDL) and
scripts to wrap your programs
HelloWorld.jdl Exe
cutable "/bin/echo" Arguments "Hello welcome
to the Grid " StdOutput "hello.out" StdError
"hello.err" OutputSandbox "hello.out","hello
.err"
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How it Works
UI Machine
Grid
Job Description
Proxy Certificate
Job
Output Sandbox
Input Data
Output Data
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The European Grid
Worldwide 267 Sites 55 Countries 101,080 CPUs 129
PB Disk
Just passed 100M CPU hrs 11,400 yrs
UK 21 Sites 15,158 CPUs 2.9 PB Disk
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Summary
New discoveries will be made at the LHC in the
next 5 years which could radically change our
understanding of the fundamental laws of nature

• Maybe answers to
• Does the Higgs exist?
• Does Supersymmetry exist?
• Is there anything in String Theory?
• Why three generations not one?
• How can Gravity be included?
• Why did all the anti-particles decay?
• Are there extra hidden dimensions?
• What fixes the masses of the particles and
  strengths of the forces?

The Standard Model explains this bit
We know almost nothing about this
We have some ideas about this bit