1. Re-creating the Big Bang
Walton, CERN and the Large Hadron Collider
Albert Einstein
Ernest Walton
Dr Cormac O’ Raifeartaigh (WIT)

2. Overview I. LHC What, why, how II. A brief history of particles
From the atom to the Standard Model
III. LHC Expectations
The Higgs boson
Beyond the Standard Model

3. CERN European Organization for Nuclear Research World leader
20 member states
10 associate states
80 nations, 500 univ.
Ireland not a member
No particle physics in Ireland

4. The Large Hadron Collider
High-energy proton beams
Opposite directions
Huge energy of collision
E = mc2
Create short-lived particles
Detection and measurement
No black holes

5. How E = 14 TeV λ =1 x 10-19 m Ultra high vacuum Low temp: 1.6 K
LEP tunnel: 27 km
Superconducting magnets

6. Particle detectors

8. Why t = 1x10-12 s Explore fundamental constituents of matter
Investigate inter-relation of forces that hold matter together
Glimpse of early universe
Answer cosmological questions
t = 1x10-12 s
V = football
Highest energy since BB

9. Cosmology
E = kT → T =

10. Particle cosmology

11. LHCb Where is antimatter? Asymmetry in M/AM decay CP violation
Tangential to ring
B-meson collection
Decay of b quark, antiquark
CP violation (UCD group)
Quantum loops

12. 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 kg: TINY

13. Atoms: centenary Maxwell (19th ct): atomic theory of gases
Dalton, Mendeleev chemical reactions, PT
Einstein: (1905): Brownian motion due to atoms?
Perrin (1908): measurements
λ =
λ =
Perrin (1908)
Einstein

14. The atomic nucleus (1911) Most projectiles through
A few deflected backwards
Most of atom empty
Atom has nucleus (+ve)
Electrons outside
Rutherford (1911)

15. Nuclear atom +ve nucleus 1911 proton (1909) Periodic Table:
determined by protons
neutron (1932)
strong nuclear force?

16. Four forces of nature Force of gravity Holds cosmos together
Long range
Electromagnetic force
Holds atoms together
Strong nuclear force: holds nucleus together
Weak nuclear force:
Beta decay
The atom

17. Splitting the nucleus Cockcroft and Walton: linear accelerator
Protons used to split the nucleus (1932)
H + Li = He + He
Verified mass-energy (E= mc2)
Verified quantum tunnelling
Nobel prize (1956)

18. 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 ( )

19. Nuclear fission fission of heavy elements Meitner, Hahn energy release
chain reaction
nuclear weapons
nuclear power

20. Strong force SF >> em protons, neutrons charge indep short range
HUP
massive particle
Yukawa pion
3 charge states

21. New particles (1950s) Cosmic rays Particle accelerators cyclotron
π + → μ ν

22. Particle Zoo
Over 100 particles

23. Quarks (1960s) new periodic table p+,n not fundamental isospin
symmetry arguments
(SU3 gauge group)
prediction of -
SU3 → quarks
new fundamental particles
UP and DOWN
Stanford experiments 1969
Gell-Mann, Zweig

24. 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,

25. 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

26. Gauge theory of e-w interaction
Unified field theory of e and w interaction
Salaam, Weinberg, Glashow
Above 100 GeV
Interactions of leptons by exchange of W,Z bosons and photons
Higgs mechanism to generate mass
Predictions
Weak neutral currents (1973)
W and Z gauge bosons (CERN, 1983)

27. The Standard Model (1970s) Matter: fermions quarks and leptons
Force particles: bosons
QFT: QED
Strong force = quark force (QCD)
EM + weak = electroweak
Prediction: W+-,Z0 boson
Detected: CERN, 1983

28. Standard Model (1970s) Success of QCD, e-w Higgs boson outstanding
many questions

29. Today: LHC expectations
Higgs boson
GeV
Set by mass of top quark, Z boson
Search

30. Main production mechanisms of the Higgs at the LHC
Ref: A. Djouadi,
hep-ph/

31. Decay channels depend on the Higgs mass:
Ref: A. Djouadi, hep-ph/

32. 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.

33. A summary plot:
Ref: hep-ph/

34. Beyond the SM: supersymmetry
Super gauge symmetry
symmetry of bosons and fermions
removes infinities in GUT
solves hierachy problem
Grand unified theory
Circumvents no-go theorems
Gravitons ?
Theory of everything
Phenomenology
Supersymmetric particles?
Broken symmetry

35. 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

36. Summary Higgs boson Close chapter on SM Supersymmetric particles
Open chapter on unification
Cosmology
Missing antimatter
Nature of Dark Matter
Unexpected particles
Revise theory

37. Epilogue: CERN and Ireland
European Organization for Nuclear Research
World leader
20 member states
10 associate states
80 nations, 500 univ.
Ireland not a member
No particle physics in Ireland