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Particle Physics

Chris Parkes & Rick StDenis

Part 1•Review: Fundamental forces and particles

•Feynman diagrams •Experimental QCD•Accelerators and Detectors •Electroweak Theory Part 2•Experimental Electroweak •Higgs searches•Top Quark •Heavy Flavour physics •Neutrinos •Beyond the Standard Model

http://ppewww.ph.gla.ac.uk/~parkes/teaching/PP/PP.html

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Fundamental Particles & Forces

• Standard Model Fermions & Bosons

• Standard Model Structure

• Common Mesons & Baryons

• Natural units

Revision of

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Particle PhysicsAim: Understand the fundamental

particles and forces of nature.

Tools: Particle colliders operating at the highest energies achievable.

It involves the biggest, most complicated experiments in the history of science, with the fastest computers, the coldest temperatures and

the strongest magnets on Earth.

Particle physics re-creates the universe just after the Big Bang and hopes to answer the questions that humans have been asking for eternity; “Where do we come from?”  “What are we made of?”

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LHC @ CERN

•27 km long tunnel,100m underground

•French/Swiss Border near Geneva

•2007 onwards Large Hadron Collider (LHC), 14 TeV proton collider

Some alternative reasons to study this course!

                     

2. I want to understand why 5000 physicist worldwide are currently building the world’s largest machine!

1. I want a nobel prize!

•Origin of mass (Higgs Boson)•New Physics (e.g. Supersymmetry)•Matter anti-matter asymmetry in Universe(CP Violation)

2 PhD places in Glasgow for Oct. 2008

2004 – QCD 2002 – neutrinos1999 – QFT 1995 -- tau / neutrino1992 -- particle detectors 1990 -- Deep Inelastic Scattering1988 -- muon neutrino 1984 -- W&Z bosons

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Standard Model – Particle Physics• Summarises the current knowledge

• Quantum theory that includes :– unified theory of weak and electromagnetic

(QED) interactions (ElectroWeak)– Strong Interactions (Quantum

chromodynamics – QCD)– Does not include gravity– Includes one boson – the Higgs – which

has not yet been discovered….

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+ Higgs boson, spin 0, electric charge 0, mass unknown yet…..

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Strength – see section on running coupling constants later

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Composite particles

•Mesons are quark anti-quark systemInteger spin particlesAbout 140 types are known

•Baryons are three quark / three anti-quark systemsAbout 120 types are known

Details of all known at http://pdg.lbl.gov/

Some common ones on the next pages

Or where the quarks hide….

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Particle SymbolAnti-particle

MakeupRest massMeV/c2

Lifetime (s)

Decay Modes

Pion π+ π- ud 139.62.60x10-8

μ+νμ

Pion π0 Self

               135.0

0.83x10-16 2γ

Kaon K+ K- us 493.71.24x10-8

μ+νμ, π+π0

Kaon K0s K0

s su 497.70.89

x10-10 π+π-,2π0

Kaon K0L K0

L su 497.75.2

x10-8π+e-νe

Rho ρ0 Self uu, dd 7700.4

x10-23 π+π-

Phi φ Self ss 102020

x10-23 K+K-,K0K0

Light Flavour Mesons

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Particle SymbolAnti-particle

MakeupRest massMeV/c2 Lifetime Decay Modes

D D+ D- cd 1869.410.6

x10-13 K + _, e + _

D D0 D0 cu 1864.64.2

x10-13 [K,μ,e] + _

D D+s D-

s cs 19694.7

x10-13 K + _

J/Psi J/ψ Self cc 3096.90.8

x10-20 e+e-, μ+μ-...

B B- B+ bu 52791.5

x10-12 D0 + _

B B0 B0 db 52791.5

x10-12 D0 + _

Bs Bs

0 Bs

0 sb 5370 ... D-s + _

Upsilon ϒ Self bb 9460.41.3

x10-20 e+e-, μ+μ-..

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Particle Symbol MakeupRest massMeV/c2 Spin

Lifetime(seconds)

Decay Modes

Proton p uud 938.3 1/2 Stable ...

Neutron n ddu 939.6 1/2 920 pe-νe

Lambda Λ0 uds 1115.6 1/22.6

x10-10 pπ-, nπ0

Sigma Σ+ uus 1189.4 1/20.8

x10-10 pπ0, nπ+

Sigma Σ0 uds 1192.5 1/2 6x10-20 Λ0γ

Sigma Σ- dds 1197.3 1/21.5

x10-10 nπ-

Delta Δ++ uuu 1232 3/20.6

x10-23 pπ+

Delta Δ+ uud 1232 3/20.6

x10-23 pπ0

Baryons -1

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Particle Symbol MakeupRest massMeV/c2 Spin

Lifetime(seconds)

Decay Modes

Delta Δ0 udd 1232 3/20.6

x10-23 nπ0

Delta Δ- ddd 1232 3/20.6

x10-23 nπ-

XiCascade

Ξ0 uss 1315 1/22.9

x10-10 Λ0π0

XiCascade

Ξ- dss 1321 1/21.64

x10-10 Λ0π-

Omega Ω- sss 1672 3/20.82

x10-10 Ξ0π-, Λ0K-

Lambda Λ+c udc 2281 1/2 2x10-13 ...

Baryons -2

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Natural Units, =c=1• Energy GeV • Momentum GeV/c (abbreviated to GeV)• Mass GeV/c2

• Length (GeV/c)-1 c=0.197GeVfm=1 [1fm=1E-15m]– Natural unit of length 1GeV-1=0.197fm

• Time (GeV/ )-1 =6.6E-25GeVs– Natural unit of time 1GeV-1=6.6E-25s

• Cross-section (GeV/c)-2 1barn=10-28m2

– Natural unit of xsec =1GeV-2=0.389mb

• Charge - ‘Heavyside-Lorenz units’ ε0=1

• Use dimensionless ‘fine structure constant’

137

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0

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c

e