Discovering the Unknown at the CERN Large Hadron Collider (LHC) Amy Gladwin University of Arizona
Discovering the Unknown at the CERN Large Hadron Collider (LHC)
Amy GladwinUniversity of Arizona
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Introduction
High energy physics or particle physics seeks to understand how the universe works at its most basic level What are the fundamental forces? What are the fundamental types of
particles (matter)? What is the nature of space and time?
Are there additional dimensions? How can we use these answers to
understand how the universe works?
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Introduction
What is the universe made of? Dark energy – 65% Dark matter – 30% Baryons (protons and neutrons) – 4% Stars – 0.5% Neutrinos – 0.5%
Dark is just another word for “dunno” so, in short, we don’t know what most of the universe is made of!!!
Fundamental Forces
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Fundamental Particles
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Fundamental Particles
Or another pattern to unravel?
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Particle AcceleratorsWe study nature using high energy
collisions between particlesParticle accelerators can be thought
of as giant microscopes that are used to study extremely small dimensions The higher the energy, the smaller the
wavelength the higher the resolving power
The higher the energy, the more massive the particles that can be created (E=mc2)
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LHC (Large Hadron Collider)CERN is
located near Geneva, Switzerland
The energy of the LHC will be 7 TeV + 7 TeV But right now
it’s 3.5 TeV + 3.5 TeV
The ring circumference is 27 km
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LHC (Large Hadron Collider)
At four points around the ring the two beams are brought together where collisions occur
The beams are actually composed of many “bunches” of protons
These bunch crossings (collisions) occur every 25 ns
At an energy of 7 TeV it takes 90μs for a proton to make one revolution
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LHC Bending Dipoles
1232 LHC superconducting dipoles
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What is the B Field?You might recall from your study of E&M
that a particle of momentum p in a uniform magnetic field B undergoes circular motion with radius R
The LHC circumference is ~27 km Packing fraction of ~64% gives R~2.8 km Thus B needed for p=7 TeV is ~8.3 T
Magnet current at this field is about 12000 A!! Magnet energy at this field is about 8000 J 1 kg of TNT has potential energy of about 5000 J This is amount of energy is substantial
GeVpTmBR 334.0
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First Beam in the LHCSept 10, 2008 in the ATLAS control
room
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September 19th IncidentAn electrical arc destroyed the busbars
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September 19th IncidentHuge magnet displacements caused by
uncontrollable evaporation of liquid helium
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Over a Year to Repair the LHC
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LHC Experiments
Particle detectors are used to record the results of these high energy collisions
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ATLAS Experiment
Visiting ATLAS
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Particle Detectors
The type of particles produced are identified by how they interact in the various detectors
The momentum of charged particles is determined by their bend in a magnetic field
The energy of most particles (except muons and neutrinos) is determined by their deposited energy in calorimenters
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Particle Detectors
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ATLAS Experiment
Z → ee Candidate
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W → e Candidate
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What’s Happening at the LHC?
Since late March, the LHC has been running at 7 TeV This is only one half the design energy
The LHC is now increasing the beam intensity By adding more protons per bunch, more
bunches, and squeezing the beam
The LHC will run until the end of 2011 Followed by a year shutdown to fix
magnet splice problems Followed by running at 14 TeV
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What’s Happening at ATLAS Now?
http://op-webtools.web.cern.ch/op-webtools/vistar/vistars.php?usr=LHC1
http://op-webtools.web.cern.ch/op-webtools/vistar/vistars.php?usr=LHC3
http://atlas-live.cern.ch/
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What Do We Hope to Discover?
Some (or none!) of the following Higgs boson Supersymmetric particles (dark matter) Extra spatial dimensions Gravitons Evidence for quark substructure Your bright ideas here
In the best scenario we will discover phenomena that no one to date has predicted or thought of
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LHC Surprises
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ATLAS at ArizonaHere at the University of Arizona we
are analyzing data from ATLAS being collected now
We are also working on electronics and detectors to be used in the next generation of experiments at the SLHC (Super LHC) It may seem odd to be working on new
electronics for an experiment that has just started to run, but the lead time for developing new ideas and then building and testing them approaches a decade!
Readout Driver (ROD)The ROD is used to collect and process
data from the liquid argon detector front-end electronics
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12 x 1 fibers
FEB (1524 modules) ROD (108 modules)
12 x 4 fibers
12 x 7 fibers
12 x 2 fibers
1Pre-Sampler
7Front
2Back
4Middle
LVL1Interface
text
text
text
ROBInterface
280 mm
320 mm
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3
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FPGA
~10 Gbps12
FPGA12
FPGA12
FPGA12
Readout Driver (ROD)The ROD must receive and process
1000 Gbits/s = 1Tbit/s !! Need state-of-the-art optics Need state-of-the-art FPGAs And be able to guess what might be
available a few years hence
In addition to managing the data, calculations must be performed on the data
And a system architecture developed to handle 200 such ROD cards
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Summer OpportunitiesWhile it’s difficult to jump right in and
begin working on the ROD design, this summer you will learn basic skills of electronics design including some of Schematic design Layout design FPGA programming Electronics debugging using external and
internal logic analyzers Data acquisition software Particle physics at the LHC
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Summer Opportunities
Data analysis If you are a very strong programmer,
you may also have an opportunity to analyze LHC data
But this demands strong C++ (or C) programming skills
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