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 particles

Fundamental forces

How can scientists probe matter at subatomic level?

Particle Acceleratora.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 spin-offs in medicine, computing and many other fields.

• Develop a Grand Unified Theory explaining the workings of the universe

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’

“Nothing exists except atoms and empty

space; everything else is opinion.”

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• All matter is made up of indivisible particles (atoms) in a great void.• Atoms are infinite in number and are perfectly solid.

John Dalton• Experimentally deduced the existence of atoms through studying gases.

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• Proposed a similar but refined version of Democritus’ atomic theory.

Anaxagoras

(500-428 BC)

Empedocles

(490-430 BC)

Democritus

(470-380 BC)

Dalton

(1766-1844)

Stoney

(1826-1911)

Planck

(1858-1947)

Thomson

(1856-1940)

George Stoney

• The first to conceive the existence of particles of electricity.

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• Accurately calculated the electron’s mass.

Joseph Thomson

• Proved the existence of electrons by studying cathode-ray tubes.

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• Measured its size and charge

Max Planck

• Founding father of Quantum Theory.

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• The Planck constant, ħ (h-bar), is a fundamental physical constant used in quantum mechanics.

~ 6.626 × 10-34 joule-seconds

Dalton

(1766-1844)

Stoney

(1826-1911)

Planck

(1858-1947)

Thomson

(1856-1940)

Rutherford

(1871-1937)

Einstein

(1879-1955)

Heisenberg

(1901-1976)

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.

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• Proved that nothing can reach the speed of light (E = mc2), or even catch up with it.

Werner Heisenberg• Developed quantum mechanics irrevocably with his Uncertainty Principle:

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Day

1000 AD

- 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.

Planck

(1858-1947)

Rutherford

(1871-1937)

Einstein

(1879-1955)

Heisenberg

(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 accelerationA step-by-step guide

1. Getting the EnergyElectrons 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. AccelerationParticles accelerated by the alternating field, with the cavity walls shielding from the decelerating effects of the microwaves.

4. Aiming the particlesThe magnets varyingly attract and repel the particles extremely quickly, with the effect that they remain travelling in a straight line.

5. The CollisionThe two groups of particles collide. The very high energy of the collision is such that the particles smash apart in to even smaller sub-particles, quarks in our case.

νμ-π

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 chambersThe 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 particlesThe 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:

– 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?• 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.