Re-creating the Big BangExperiments at the Large Hadron Collider

Dr Cormac O’ Raifeartaigh (WIT)

Albert Einstein

Ernest Walton

Overview

I What

II Why

III How

IV A brief history of atoms

V Expectations

I The Large Hadron Collider

A particle accelerator

‘Atom smasher’

Particles created

Detected

LHC at CERN, Geneva

How

High speed proton beams

Opposite directions - collisions

Huge energy of collision

Create short-lived particles

Detection and measurement E = mc2

HOW

27 km

Energy: 14 TeV

Low temp: 1.6 K

Ultra high vacuum

Why

Explore fundamental constituents of matter

Investigate forces that hold matter together

Glimpse of early universeHighest energy since BB

Are the forces of the universe related ?

•Gravity caused by sun’s mass

Newton (1642-1727)

•Planet orbits due to gravity

Newton’s gravity

2r

MmGF

•Terrestrial gravity due to earth’s mass

Four forces of nature Force of gravityHolds cosmos togetherLong range

Electromagnetic force Holds atoms together

Strong nuclear force: holds nucleus together

Weak nuclear force: radioactivity

The atom

A brief history of atoms

Democritus (600 BC): matter made of atoms

Dalton (19th ct): Mendeleev (19th ct):

chemical reactions

A brief history of atoms

Maxwell (19th ct): atomic theory of gases

Einstein: (1905): Brownian motion due to atoms?

Perrin (1908): verified

Brownian motionEinstein Perrin

The atomic nucleus

•Most projectiles through

•A few deflected backwards

•Atom has nucleus

•Electrons outside

Rutherford (1911)

Nuclear model of the atom

nNu

•Nucleus (+ve): •Electrons (-ve): orbiting •Force: electromagnetic

•Protons (1909)•Nucleus (1911)•Neutrons (1932)?

Atom

Nucleus

Nuclear force: stronger than electromagnetic?

Splitting the nucleus

Cockcroft and Walton: particle accelerator

Particles used to split the nucleus (1932)

Nobel prize (1956)

H + Li = He + He

Verified mass-energy (E= mc2)Verified quantum tunnelling

Nuclear fission

Meitner, Hahn: nuclear fission

Energy released

•Chain reaction•Nuclear bomb

•Nuclear power•Nuclear power stations

New particles

Cosmic rays New particle accelerators

cyclotron

Particle Zoo

Over 100 particles

The quark model

New periodic tableNew fundamental particle

Proton not fundamental Inner structure

Symmetry argumentsQuarks

Murray Gellmann

Quarks and leptons

Six different quarks(u,d,s,c,t,b)

Six leptons

(e, μ, τ, υe, υμ, υτ)

Particles of matter: fermions

Two extra generations

The Standard Model

Matter: leptons and quarks

Force carriers: bosons

EM + weak = electroweak

Strong force = quark force

Higgs fieldParticle massesHiggs boson

LHC: expectations

Higgs boson

120-180 GeV

Set by mass of top quark, Z boson

Explain masses for other particles

Beyond the standard model

Unification of 3 forces

Grand unified theory

Supersymmetry

Supersymmetric particles?

Unification of 4 forces

Theory of everything

String theory

Extra dimensions

LHC and cosmology

√ 1. Exotic particles

√ 2. Unification of forces

3. Nature of dark matter?

4. Missing antimatter?

LHC = photo of early U

3. Summary

Higgs bosonClose chapter on SM

Supersymmetric particlesOpen chapter on unification

WIMPSExplain Dark Matter

Unexpected particlesRevise theory

Epilogue: CERN

World centre for particle physics

20 member states

10 associate states

Ireland not a member

No particle physics in Ireland

Organization for Nuclear research