Transcript The Big Bang, the LHC and the God Particle Dr Cormac O’Raifeartaigh (WIT) The Big Bang, the LHC and the God Particle Cormac O’Raifeartaigh.

The Big Bang, the LHC and the God Particle
Dr Cormac O’Raifeartaigh (WIT)
The Big Bang, the LHC and the God
Particle
Cormac O’Raifeartaigh (WIT)
Overview
I. LHC
What, why, how
II. A brief history of particles
From atoms to the Standard Model
III. LHC Expectations
The God particle
Beyond the Standard Model
Cosmology at the LHC
The Large Hadron Collider (CERN)
Particle accelerator
Head-on collision
Huge energy density
Create short-lived particles
E = mc2
No black holes
Detection
How
Ultra high vacuum
Low temp: 1.6 K
v = speed of light
E = 14 TeV (2.2 µJ)
LEP tunnel: 27 km
Superconducting magnets
600 M collisions/sec (1.3 kW)
Why
I. Explore fundamental constituents
of matter
Investigate inter-relation of forces
that hold matter together
II. Study early universe
Highest energy since BB
T = 1019 K
t = 1x10-12 s
V = football
• Puzzle of antimatter
• Puzzle of dark matter
Cosmology
E = kT → T =
Particle detectors
4 main detectors
• CMS
multi-purpose
•ATLAS multi-purpose
•ALICE quark-gluon plasma
•LHC-b antimatter decay
Particle detectors
Tracking device
measures momentum of charged
particle
Calorimeter
measures energy of particle by
absorption
Identification detector
measures velocity of particle by
Cherenkov radiation
• 9 accelerators
• recycling
• velocity increase?
K.E = 1/2mv2
m
m0
1 v
2
c2
Applications
Computer science
Data analysis
World Wide Web
Platform for sharing data
Hospital physics
Accelerators
Positron Emission Tomography (PET)
GRID
Distributed computing
Tim Berners-Lee
II Particle physics (1930s)
• electron (1895)
• atom (1909)
• nuclear atom (1911)
Rutherford Backscattering
• proton (1918)
• neutron (1932)
• what holds nucleus together?
• what holds electrons in place?
• what causes radioactivity?
Protons and the Periodic Table
• Fundamental differences
no. protons in nucleus
• Determines no. electrons
• Determines chemical properties
what holds nucleus together?
Strong force
strong force >> em
charge indep (p+, n)
short range
Heisenberg Uncertainty
massive particle
3 charge states
Yukawa pion (π)
Yukawa
Four forces of nature
Force of gravity
Holds cosmos together
Long range
Electromagnetic force
Holds atoms together
Strong nuclear force: holds
nucleus together
The atom
Weak nuclear force:
Beta decay
New particles (1950s)
Cosmic rays
π+ → μ+ + ν
Particle accelerators
LINACS (Walton)
synchrotrons
Particle Zoo (1950s, 1960s)
Over 100 particles
Quarks (1960s theory)
p not fundamental
new periodic table
symmetry arguments
new fundamental particles
quarks
Up, down, strange
prediction of  -
Gell-Mann, Zweig
Quarks (experiment, 1970s)
Stanford experiments 1969
Scattering experiments
Similar to RBS
SF = interquark force!
defining property = colour
confinement
infra-red slavery
The energy required to produce a separation far exceeds
the pair production energy of a quark-antiquark pair
Quark generations (1970s –1990s)
30 years experiments
Six different quarks
(u,d,s,c,t,b)
Six leptons
(e, μ, τ, υe, υμ, υτ)
Gen I: all of ordinary matter
Gen II, III redundant?
Electro-weak force (1970s)
Electromagnetic + weak forces = e-w force
Single interaction above 100 GeV
Mediated by new particles
Higgs mechanism to generate mass
Predictions
• W and Z gauge bosons (CERN, 1983)
• Higgs boson (the God particle)
Rubbia and van der Meer
Nobel prize 1984
The Origin of Mass
The strong nuclear force cannot explain the mass of the electron
though…
Or very heavy quarks
top mass = 175 proton mass
The Higgs Boson
We suspect the vacuum is full of another sort of matter that is
responsible – the higgs…. a new sort of matter – a scalar?
To explain the W mass the higgs vacuum must be 100 times
denser than nuclear matter!!
It must be weak charged but not electrically charged
The Standard Model (1970s)
Strong force = quark force (QCD)
EM + weak force = electroweak
Matter particles: fermions
Force particles: bosons
Prediction: W+-,Z0 boson
Detected: CERN, 1983
Standard Model: 1980-1990s
• experimental success but Higgs boson outstanding
key particle: too heavy?
III LHC expectations (SM)
Higgs boson
Determines mass of other
particles
120-180 GeV
Set by mass of top quark, Z
boson
Search…surprise?
Main production mechanisms of the Higgs at the LHC
Ref: A. Djouadi,
hep-ph/0503172
Higgs search: summary
Ref: hep-ph/0208209
Expectations II: Beyond the SM
Unified field theory
Grand unified theory (GUT): 3 forces
Theory of everything (TOE): 4 forces
Supersymmetry
symmetry of fermions and bosons
improves GUT (circumvents no-go theorems)
gravitons: makes TOE possible
LHC
Supersymmetric particles?
Extra dimensions?
Expectations III: Cosmology
1.
Superforce:
SUSY particles?
2. SUSY = dark matter?
neutralinos?
double whammy
3. Missing antimatter ?
LHCb
High E = photo of early U
LHCb (UCD)
• 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)
Summary
Higgs boson (God particle)
Close chapter on SM
Supersymmetric particles
Open chapter on unification
Cosmology
Missing antimatter
Nature of dark matter
Surprises
New dimensions - string theory?
Further reading: ANTIMATTER
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…..almost