Recreating the Big Bang with the World’s Largest Machine Prof Peter Watkins Head of Particle...

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.