Recreating the Big Bang with the World’s Largest Machine

Prof Peter Watkins

Head of Particle Physics Group

The University of Birmingham

Admissions Talk2nd December 2008

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Somewhere in Switzerland…

Situated on the Swiss-French border, near GenevaIs the World’s largest physics laboratory

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CERN

Deep underground, they are building the World’s largest machine

Geneva

French Alps

Which will accelerate sub-atomic particles to 0.999999991 the speed of light ….

The Large Hadron Collider (LHC)

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Large Hadron Collider

…. and collide them together in four cathedral-sized caverns around the 27 km ring.

Creating sub-atomic explosions, and conditions that existed less than a billionth of a second after the Big Bang.

In massive particle detectors

600 million times per second

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The LHC

Let’s start at the beginning…..

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Building Blocks of Matter

All matter around us is made of atoms. Atoms consist of a positive nucleus (containing 99.98% of the atom’s mass) and a cloud of electrons.

Nuclei consist of protons and neutrons. The protons and neutrons are made of three quarks.

in metresWe know

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Elementary Particles

Protons and neutrons are made from two types of quarks: Up (u) and Down (d).

u-quarks have electric charge +2/3 while d-quarks have charge –1/3 (electron has electric charge -1 in these units).

U+2/3

U+2/3

d-1/3

Proton

U+2/3

d-1/3

d-1/3

Neutron

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Family of Particles

So, there is a family of particles:

Up quark (u) Down quark (d) Electron (e-) Electron neutrino (e)

Mass ~ 0.003 ~ 0.006 = 0.0005 < 10-8 ?(relative to the mass of a single proton)

Everything around us (the whole Periodic Table) is made up of these four particles.

So, that’s nice and simple then!

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BUT….le

pto

ns

qu

ark

s up

down

e

e

strange

charm

bottom

top

Nature supplies us with two extra families that are very much heavier:

We don’t know why!

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The Standard Model

u

d s

c

b

t

e

e

quarks

leptons

}

}

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The Weak Force

u

d s

c

b

t

e

e

quarks

leptons

}

}W+

W-

Z0

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The Electromagnetic Force

u

d s

c

b

t

e

e

quarks

leptons

}

}

Photon

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The Strong Force

u

d s

c

b

t

e

e

quarks

leptons

}

}g

gluon

Gravity too weak to even consider an the atomic scale

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Antimatter

Every fundamental particle has its antiparticle. These have the same mass but opposite charge.

e- e+

u+2/3 u-2/3

electron positron

up quark up anti-quark

Etc.

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Dark Matter

The visible Universe (made from u, d, e, ) only accounts for about 4% of its measured mass.

What makes up the rest?

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Other Questions – What is Mass?

In the mid 1960s, British physicist Peter Higgs came up with a theory on why some particles have mass.

He proposed a new heavy particle, now called the Higgs, which generates a Higgs field.

Particles who ‘feel’ this field gain mass. Light particle don’t feel this field strongly, heavy particles do.

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Many More Questions …

What is mass?

4 forces?

12 matter particles?

What about gravity?

Where did all the

antimatte

r go?

Mini black holes?

How many dimensions?

What about the other 96% of the universe …..

Why no free quarks?

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How do we find answers? ….

….powerful particle accelerators

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LHC - Facts

• 27 km circumference • Each proton goes around the 27km ring over

11,000 times a second.• Energy of proton beam in LHC > 0.3 GJ

(family car travelling at 1000 mph)• Energy stored in magnets > 1 GJ• Super-conducting magnets cooled to ~ 1.9 K

(colder than Outer Space).

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Modern Detectors

ATLAS Detector(one of the four main LHC detectors)

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Summary

Particle physics has discovered much about how the Universe works

Still many outstanding questionsThe World’s largest machine (LHC) will add to

this knowledgeHuge challenges aheadBut LHC will find new & exciting physicsWe will learn more about the very early UniverseBirmingham will play an important role in this.Thank you for listening.