Re-creating the Big BangWalton, CERN and the Large Hadron Collider

Dr Cormac O’ Raifeartaigh (WIT)

Albert Einstein

Ernest Walton

Overview

I. LHC

What, why, how

II. A brief history of particlesFrom the atom to the Standard Model

III. LHC Expectations

The Higgs boson

Beyond the Standard Model

CERN

World leader

20 member states

10 associate states

80 nations, 500 univ.

Ireland not a member

No particle physics in Ireland

European Organization for Nuclear Research

The Large Hadron Collider

No black holes

High-energy proton beams

Opposite directions

Huge energy of collision

E = mc2 Create short-lived particles

Detection and measurement

How

E = 14 TeV

λ =1 x 10-19 m

Ultra high vacuum

Low temp: 1.6 K

LEP tunnel: 27 km Superconducting magnets

Particle detectors

2

2

0

1c

v

mm

Why

Explore fundamental constituents of matter

Investigate inter-relation of forces that hold matter together

Glimpse of early universe

Answer cosmological questions

Highest energy since BB t = 1x10-12 s

V = football

Cosmology

E = kT → T =

Particle cosmology

LHCb

Tangential to ringB-meson collectionDecay of b quark, antiquarkCP violation (UCD group)

• Where is antimatter?• Asymmetry in M/AM decay• CP violation

Quantum loops

Discovery of electron

Crooke’s tube

cathode rays

Perrin’s paddle wheel

mass and momentum

Thompson’s B-field

e/m

Milikan’s oil drop

electron charge

Result: me = 9.1 x 10-31 kg: TINY

Atoms: centenary

Maxwell (19th ct): atomic theory of gases

Dalton, Mendeleev chemical reactions, PT

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

Perrin (1908): measurements

Einstein Perrin (1908)

λ =

λ = trN

RT

A3

The atomic nucleus (1911)

• Most projectiles through

• A few deflected backwards

• Most of atom empty

• Atom has nucleus (+ve)

• Electrons outside

Rutherford (1911)

Nuclear atom

• neutron (1932)

• +ve nucleus 1911

• proton (1909)

• strong nuclear force?

Periodic Table: determined by protons

Four forces of nature Force of gravityHolds cosmos togetherLong range

Electromagnetic force Holds atoms together

Strong nuclear force: holds nucleus together

Weak nuclear force: Beta decay

The atom

Splitting the nucleus

Cockcroft and Walton: linear accelerator

Protons used to split the nucleus (1932)

Nobel prize (1956)

H + Li = He + He

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

Ernest Walton (1903-95)

Born in Dungarvan

Early years

Limerick, Monagahan, Tyrone

Methodist College, Belfast

Trinity College Dublin (1922)

Cavendish Lab, Cambridge (1928)

Split the nucleus (1932)

Trinity College Dublin (1934)

Erasmus Smith Professor (1934-88)

Nuclear fission

fission of heavy elements Meitner, Hahn

energy release

chain reaction

nuclear weapons

nuclear power

Strong force

SF >> em

protons, neutrons

charge indep

short range

HUP

massive particle

Yukawa pion

3 charge states

New particles (1950s)

Cosmic rays Particle accelerators

cyclotronπ + → μ + + ν

Particle Zoo

Over 100 particles

Quarks (1960s)

new periodic tablep+,n not fundamental isospinsymmetry arguments (SU3 gauge group)prediction of -

SU3 → quarksnew fundamental particlesUP and DOWN

Stanford experiments 1969

Gell-Mann, Zweig

Quantum chromodynamics

scattering experiments

colour

chromodynamics

asymptotic freedom

confinement

infra-red slavery

The energy required to produce a separation far exceeds the pair production energy of a quark-antiquark pair,

Quark generations

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

Six leptons

(e, μ, τ, υe, υμ, υτ)

Gen I: all of matter

Gen II, III redundant

Gauge theory of e-w interaction

Unified field theory of e and w interactionSalaam, Weinberg, Glashow

Above 100 GeVInteractions of leptons by exchange of W,Z bosons and photonsHiggs mechanism to generate mass

Predictions• Weak neutral currents (1973)• W and Z gauge bosons (CERN, 1983)

The Standard Model (1970s)

Matter: fermionsquarks and leptons

Force particles: bosonsQFT: QED

Strong force = quark force (QCD)

EM + weak = electroweak

Prediction: W+-,Z0 boson

Detected: CERN, 1983

Standard Model (1970s)

• Success of QCD, e-w• Higgs boson outstanding many questions

Today: LHC expectations

Higgs boson

120-180 GeV

Set by mass of top quark, Z boson

Search

Main production mechanisms of the Higgs at the LHC

Ref: A. Djouadi,hep-ph/0503172

Decay channels depend on the Higgs mass:

Ref: A. Djouadi, hep-ph/0503172

For low Higgs mass mh 150 GeV, the Higgs mostly decays to two b-quarks, two tau leptons, two gluons and etc.

In hadron colliders these modes are difficult to extract because of the large QCD jet background.

The silver detection mode in this mass range is the two photons mode: h , which like the gluon fusion is a loop-induced process.

Ref: hep-ph/0208209

A summary plot:

Beyond the SM: supersymmetry

Super gauge symmetrysymmetry of bosons and fermionsremoves infinities in GUTsolves hierachy problem Grand unified theory

Circumvents no-go theoremsGravitons ?Theory of everything

Phenomenology Supersymmetric particles?Broken symmetry

Expectations III: cosmology

√ 1. Exotic particles

√ 2. Unification of forces

3. Missing antimatter? LHCb

4. Nature of dark matter?neutralinos?

High E = photo of early U

SummaryHiggs bosonClose chapter on SM

Supersymmetric particlesOpen chapter on unification

CosmologyMissing antimatterNature of Dark Matter

Unexpected particlesRevise theory

Epilogue: CERN and Ireland

World leader

20 member states

10 associate states

80 nations, 500 univ.

Ireland not a member

No particle physics in Ireland

European Organization for Nuclear Research