Transcript Particle Physics Timeline - University of Birmingham

Recreating the Early
Universe at the LHC
King Edward’s School, Bath
Particle Physics
• Particle physics aims to answer the BIG
questions about the Universe by
studying space and matter at its smallest
level
• If a helium atom was the size of a
large city, each proton and neutron
would be the size of a person, and each
quark and electron would be smaller
than a tiny freckle.
The Standard Model:
“Ingredients for a Universe”
Fundamental forces
Fundamental particles
How can scientists probe matter at subatomic level?
Particle Accelerator
a.k.a. the Particle Smasher
• A particle smasher
accelerates particles to high
speeds and collides them.
• The particles then decay into
subatomic parts and emit
radiation.
• Their paths are detected
CERN – European Organisation for
Nuclear Research
First experiments carried out at CERN concerned
the inside of the atom – hence organisation for
‘Nuclear’ Research
2,500 people work at CERN. However, thousands
more scientists across the globe are connected to
research being carried out here.
Revolutionary technology has been created at CERN
- The Web was invented at CERN in 1990
The LHC will be switched on for the first time in
May 2008!
Recreating the early Universe: Why?
• Scientific curiosity –
Answering questions about
Life, the Universe and
Everything!
• Scientific ambition – how far
can experimental work take
us?
• Technology developed for the
LHC project could have spinoffs in medicine, computing
and many other fields.
• Develop a Grand Unified
Theory explaining the
workings of the universe
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Anaxagoras of Clazomenae
Widely recognised as the first major
Greek philosopher come scientist.
“There is no smallest among the small and no largest among
the large, but always something still smaller and still larger”
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Empedocles of Acragas
Held the belief that all existence consisted of 4 elements.
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Democritus of Abdera
An advocate of the ‘atomist
doctrine’
• All matter is made up of indivisible
particles (atoms) in a great void.
• Atoms are infinite in number and
are perfectly solid.
“Nothing exists except atoms and empty space;
everything else is opinion.”
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John Dalton
• Experimentally deduced the
existence of atoms through studying
gases.
• Proposed a similar but refined version
of Democritus’ atomic theory.
Anaxagoras
Empedocles
Democritus
Dalton
Stoney
Thomson
(500-428 BC)
(490-430 BC)
(470-380 BC)
(1766-1844)
(1826-1911)
(1856-1940)
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George Stoney
• The first to conceive the
existence of particles of
electricity.
• Accurately calculated the
electron’s mass.
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Joseph Thomson
• Proved the existence of
electrons by studying cathode-ray
tubes.
• Measured its size and charge
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Max Planck
• Founding father of Quantum Theory.
• The Planck constant, ħ (h-bar), is a
fundamental physical constant used
in quantum mechanics.
~ 6.626 × 10-34 joule-seconds
Stoney
Thomson
Planck
Rutherford
Einstein
Heisenberg
(1826-1911)
(1856-1940)
(1858-1947)
(1871-1937)
(1879-1955)
(1901-1976)
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Ernest Rutherford
• Introduced the concept of an
atomic nucleus and experimentally
proved its existence.
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Albert Einstein
• Introduced the concept of
photons, leading to the modern
view of wave-particle duality in
light.
• Proved that nothing can
reach the speed of light (E =
mc2), or even catch up with it.
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Werner Heisenberg
• Developed quantum mechanics
irrevocably with his Uncertainty
Principle:
- It is impossible to locate both the
position and the momentum of a
particle with precision.
- Probability distributions must
be used to estimate these
factors.
Rutherford
Einstein
Heisenberg
(1871-1937)
(1879-1955)
(1901-1976)
Mass-discovery of
sub-atomic particles
Current Knowledge
The Big Bang
• This occurred about 14 billion years ago
• The universe began from a miniscule point
• The fundamental forces were combined at this stage
The Hubble Telescope
Gravity
• Why is gravity so much weaker than the
other fundamental forces?
• Are extra dimensions the answer?
Particle acceleration
A step-by-step guide
1. Getting the Energy
Electrons slow down
as they travel through
the Klystron, emitting
microwaves as their
speed varies.
2. Particle generation
Particles are knocked
from their atoms
using lasers or
electron guns.
3. Acceleration
Particles accelerated
by the alternating
field, with the cavity
walls shielding from
the decelerating
effects of the
microwaves.
4. Aiming the particles
The magnets varyingly
attract and repel the
particles extremely
quickly, with the
effect that they
remain travelling in a
straight line.
5. The Collision
The two groups of
particles collide. The
very high energy of
the collision is such
that the particles
smash apart in to
even smaller subparticles, quarks in
our case.
ν
μπ
6. Detecting the particles
Any charged or high energy particles will
ionise atoms they come into contact with,
and we can detect the trails of ions these
particles leave behind them, e.g. with a
cloud or bubble chamber.
Cloud and Bubble chambers
The particles ionise
the atoms they travel
past, which in turn
attract the particles
which visibly change
their state, allowing
us to see the trails of
the particles.
‘Seeing’ different particles
The particles curve
different ways, at
varying amounts and
velocities. Analysing
these variables allow
us to work out what
kind of particle it is.
What are we looking for?
• Standard model
• Higgs Boson
• Other particles:
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Strangelets
Micro black holes
Magnetic monopoles
Supersymmetric particles
Standard Model
• It predicts that one more particle is to be
discovered, the Higgs Boson.
• By completing the standard model, some
physicists hope to extend it into a ‘theory
of everything’.
Higgs Boson
• It would provide the
mechanism by which
particles acquire mass.
• Accelerators have not
produced a Higgs
boson.
• In order for physicists
to develop their
understanding of the
matter, there needs to
be progress in the
search for the Higgs
boson.
Other Particles
• Other theorized particles may be
produced at the LHC, and searches for
some of these have been planned.
• Some examples of these particles are:
–
–
–
–
Strangelets
Micro black holes
Magnetic monopoles
Supersymmetric particles
Where will it lead?
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•
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Grand Unified Theory
Why is Gravity So ‘Weak’?
Technological Developments
International Linear Collider
Grand Unified Theory
• Physicists have linked two of the four
fundamental forces with electroweak
theory (in 1979).
• Grand unification theories (GUTs) have
tried to link a strong force to these two
forces.
• The creation of a GUT would be a
breakthrough in particle physics.
Why is Gravity So ‘Weak’?
• The Higgs boson may help to explain why gravity
is so much weaker than the other three
fundamental forces.
• By developing a greater understanding of where
the fundamental forces originated from,
physicists hope to understand how and why they
differ.
Technological Developments
• The creation of the LHC has led to many
technological developments, as new equipment
is needed to fulfil functions that have not been
necessary before.
• Examples include:
– Positron emission tomography (PET)
• A nuclear imaging technique used in medicine to
create a 3D image of functional processes in the
body
• PET cameras were first used in CERN in the 1970s
Technological Developments
– World Wide Web
• Created by Sir Tim Berners-Lee, in 1989
• At that time he was working at CERN and used the
service to share information with other academics
– The GRID
• A service used to share computer power and data
storage capacity over the Internet
• The data will be produced at about 10 Petabytes a
year.
International Linear Collider (ILC)
• The ILC is a proposed electron-positron
collider, which will work with the LHC, to
provide more precision and help discover
more.
• They will work together to understand
particle physics beyond the standard
model.