Transcript Discovering the Unknown at the CERN Large Hadron Collider (LHC)

Discovering the Unknown at the
CERN Large Hadron Collider (LHC)
Introduction
High energy physics or particle physics
seeks to understand how the universe
works at its most basic level
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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?
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Dark energy – 65%
Dark matter – 30%
Baryons (protons and neutrons) – 4%
Stars – 0.5%
Neutrinos – 0.5%
In short, we don’t know what most of
the universe is made of!!
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Fundamental Forces
Interactions arise from
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Fields (classical field theory)
Exchanged quanta (quantum field theory)
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Fundamental Forces
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Bosons
Gauge bosons are the exchange
particles for the four forces
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Leptons
 There are three
families of leptons
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The electron is
familiar to you
Muons and taus are
heavy electrons
 There are flavors of
neutrinos associated
with each of the
electron, muon, and
tau
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Quarks
 There are three
families of quarks
 Free quarks do not
exist but they
combine to make up
particles like
protons, neutrons,
and pions
 You are essentially
made of up and
down quarks and
electrons
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Deciding on the goals of the Experiment:
understanding the underlying patterns of matter
Everyday life is messy and chaotic, but the underlying
laws of nature tend to be simple and show striking
underlying regularities or symmetries. Many experiments
seek to understand these symmetries
In Biology, all of life (DNA, RNA) is based on combinations
of just 4 molecular bases (A, C, G, T ), arranged in coded
sequences.
Seeking the underlying patterns of matter
In Chemistry, all the types of molecules we see are made from
just 92 naturally occuring elements (the Periodic Table)
And these have only a
few natural families
(e.g. H, Li, Na, K, Rb,
Cs, Fr all have one free
valence electron) with
similar chemical
properties.
Seeking the underlying patterns of matter
The basic constituents of matter are
the 6 quarks and the 6 leptons, and
the 4 carriers of the fundamental
forces. The three quark and lepton
generations have very similar
properties.
All the particles we know of (protons,
neutrons, nuclei, atoms are made
from these simple building blocks.
As far as we know, there are no
smaller units than quarks and leptons.
Particle Accelerators
We study nature by using high energy
collisions between particles
Particle accelerators can be thought of
as giant microscopes that are used to
study extremely small dimensions
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The higher the energy the smaller the
wavelength the better the resolution
Particle detectors are used to record the
results of these high energy collisions
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CERN LHC (Large Hadron Collider)
 CERN is located
outside Geneva,
Switzerland
 The energy of
the LHC will be
7 TeV x 7 TeV
 The
circumference
of the ring is 27
km
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Bending
 You might recall from your study of E&M and
mechanics that to keep a particle of
momentum p in circular motion with radius r, a
B field is needed
Br Tm  0.334 pGeV 
 The LHC circumference is ~27 km
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Packing fraction of ~64% gives r~2.8 km
Thus B needed for p=7 TeV is ~8.3 T
The use of superconducting magnets using
superfluid He at 1.8K are needed to reach this field
 Final magnet current is 11850 A
 Bending achieved by 1232 15-m dipoles
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Bending
LHC dipoles
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Bending
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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
LHC
LHC
LHC Experiments
ATLAS
LHC
LHC
LHC
ATLAS
LHC
ATLAS
ATLAS
ATLAS
CERN LHC
The
experiments
(detectors) are
located 100m
underground
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ATLAS Experiment
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ATLAS Experiment
CSC
Chambers
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October 2004
February 2004
July 2005
October 2004
November 2005
October 2006
February 2006
July 2007
September 2006
September 2007
February 2008
An historical moment
Closure of the LHC beam pipe ring
on 16th June (the last piece was the
one shown here in ATLAS)
ATLAS Experiment
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Closing the Beam Pipe
History of the Universe
Particle Detectors
The type of particles produced are
identified by how they interact in the
various detectors
The momentum of charge particles is
determined by their bend in a magnetic
field
The energy of most particles (except
muons and neutrinos) is determined by
their shower energy in calorimenter
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Particle Detectors
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Particle Detectors
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Triggers
Because collisions are occurring every
25ns we cannot record to tape/disk all
of them
We use electronic and software triggers
to select only the interesting events
(collisions)
Compare an uninteresting and an
interesting one
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Rejeter!
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muon
électron
Accepter!
électron
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Higgs Boson
 You may have read somewhere that the one
of the primary physics goals at the LHC is to
discover the Higgs or the “god particle”
 The standard model in particle physics works
wonderfully well but the underlying theory
involves only massless particles!
 The Higgs field is a hypothesis about the way
particles (electrons, protons, …) acquire mass
 Because particles do have mass, confirming
or rejecting this hypothesis is critically
important
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Higgs Boson
Dark Matter
Higgs Boson as an Actress
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Higgs Boson Decay Modes
 The Higgs boson decays to the heaviest
particles possible allowed by energy
conservation
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Higgs Boson Discovery
Nobody knows
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ATLAS at Arizona
Here at the University of Arizona we are
working on software in anticipation of
first collisions in 2008
But we are also working on electronics
to be used at the next generation
collider called the SLHC (Super LHC)
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It may seem odd to be working on new
electronics for an experiment that has not
even run yet, but the lead time for
developing new ideas approaches a
decade!
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Readout Driver (ROD)
 The ROD is used to collect and process data
from the liquid argon detector front-end
electronics
FEB (1524 modules)
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Pre-Sampler
ROD (108 modules)
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12 x 1 fibers
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Front
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~10 Gbps
FPGA
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FPGA
12 x 7 fibers
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Middle
12 x 4 fibers
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Back
12 x 2 fibers
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FPGA
LVL1
Interface
ROB
Interface
320 mm
t
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x
t
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x
tt
e
x
t
14
12
FPGA
280 mm
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Readout Driver (ROD)
The ROD must receive and process
1000 Gbits/s = 1Tbit/s !!
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Need state-of-the-art optics
Need state-of-the-art FPGAs
And be able to gauge 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
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handle 100 such ROD cards
Summer Opportunities
While it’s difficult to jump right in and
begin working on the ROD design, this
summer we will teach you basic skills of
electronics design including some of
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Schematic design
Layout design
FPGA programming
Electronics debugging using external and
internal logic analyzers
Data acquisition software
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From Basic Research to Society
65% of the US GDP derives from government investment in
basic research. Some examples:
 Discovery in 1920’s of quantum bundles of matter and
energy was revolutionary in science but of no foreseeable
use. It led however to the modern electronics, computers
and communications that are central to modern life.
 In the late 19th century, physicists observed superconductivity
as a scientific curiosity. It re-emerged as the basis for powerful
superconducting magnets for MRI, the levitation of trains, and
power transmission, led by Fermilab’s development for Tevatron.
 Chemists sought to make new organic molecules to see
what configurations were possible. In time, this spawned
huge plastics and pharmaceutical industries.
Tools from Physics Research
 Medical imaging tools – Magnetic
Resonance Imaging (MRI), PET scan
detectors, tracer nuclides, CAT
scans are derived from techniques
invented for research.
 Parallel computing – the use of
many computers to attack different
parts of a problem simultaneously –
was invented by scientists who
needed faster real-time processing
of data. Such techniques are now
the mainstay of weather forecasting
and market trend analyses.
Accelerators for Society
Particle accelerators were devised to
produce high energy probes for
studying the atom.
Now they are used for medical
therapy, medical diagnostics, materials
research, making electronic circuits,
nuclear waste disposal and food
sterilization.
Accelerators for Society
CATEGORY OF ACCELERATORS
NUCLEAR AND PARTICLE PHYSICS
High e nergy accelerators
BIOMEDICAL ACCELERATORS
Radiotherapy
(Biomedical) research
Medical radioisotope p roduction
INDUSTRIAL ACCELERATORS
Industrial electron accelerators
Ion implanters
Surface modification centers and research
SYNCHROTRON RADIATION SOURCES
Estimated total
NUMBERS
IN USE
112
>4000
800
~200
~1500
>2000
~1000
~50
~10000
Communication
The World Wide Web was invented by the particle
physics laboratory CERN to enable far-flung
collaborations to communicate information and make
large data sets available around the world.
1 $Trillion
Tim Berners-Lee
The commercial impact of the Web has grown exponentially,
and has transformed the way we get information.
Experiments in Particle Physics
The experiments at Fermilab’s accelerators:
 Explore the way the universe is constructed, and find the
laws that govern it
 Train young people with skills to solve new problems
 Stimulate technological advances that will benefit society
We take great pleasure in doing them and
learning about our world; we hope that what
we do is of importance to you as well !