2nd Term 2010 The Standard Model of Particle Physics – Christian Schwanenberger – University of Manchester 1

Christian SchwanenbergerChristian SchwanenbergerTel.: +44 161 306-6466Tel.: +44 161 306-6466 +1 630 840-4242+1 630 840-4242

Fax: Fax: +1 630 840-6650 +1 630 840-6650 schwanen@fnal.govschwanen@fnal.gov

http://www-d0.fnal.gov/~schwanenhttp://www-d0.fnal.gov/~schwanen

22ndnd term 2010 term 2010

The Standard Model The Standard Model of Particle Physicsof Particle Physics

2nd Term 2010 The Standard Model of Particle Physics – Christian Schwanenberger – University of Manchester 2

ContentContent

1.1. Introduction Introduction

2.2. Basics of Quantum Field Theory Basics of Quantum Field Theory

3.3. Quantum Electrodynamics, QED Quantum Electrodynamics, QED 3.13.1 Classical Field Theory Classical Field Theory 3.23.2 The Lagrange density of QED The Lagrange density of QED 3.33.3 The Feynman rules of QED The Feynman rules of QED 3.43.4 Renormalisation in QED Renormalisation in QED

4.4. Quantum Chromodynamics, QCD Quantum Chromodynamics, QCD 4.14.1 The Lagrange density of QCD The Lagrange density of QCD 4.24.2 The Feynman rules of QCD The Feynman rules of QCD 4.34.3 Asymptotic freedom Asymptotic freedom 4.44.4 Confnement Confnement 4.54.5 Quarkonium physics Quarkonium physics

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ContentContent

5.5. Quantum Flavour Dynamics (QFD) Quantum Flavour Dynamics (QFD) 5.15.1 The Gauge Group of QFD The Gauge Group of QFD 5.2 5.2 The Higgs feld and spontaneous symmetry The Higgs feld and spontaneous symmetry breaking breaking

5.35.3 Extension of QFD to more fermions and Extension of QFD to more fermions and efective low energy coupling efective low energy coupling 5.45.4 The mass matrix and the CKM matrix The mass matrix and the CKM matrix 5.55.5 The Feynman rules of QFD The Feynman rules of QFD

6.6. Higgs Physics Higgs Physics 6.16.1 Higgs properties Higgs properties 6.26.2 Decay modes Decay modes 6.36.3 Production mechanism at Tevatron/LHC Production mechanism at Tevatron/LHC

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ContentContent

Exercises:Exercises:33 problem sheets problem sheets33 tutorials if you like... tutorials if you like...

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LiteratureLiterature

Introduction to Quantum Field Theory, Introduction to Quantum Field Theory, J. Forshaw webpageJ. Forshaw webpage An Introduction to Quantum Field Theory,An Introduction to Quantum Field Theory, Peskin and SchroederPeskin and Schroeder Quarks and Leptons,Quarks and Leptons, Halzen & MartinHalzen & Martin Introduction to Gauge Field Theory,Introduction to Gauge Field Theory, Bailin & LoveBailin & Love Gauge Theory of Elementary Particle Physics,Gauge Theory of Elementary Particle Physics, Cheng & LiCheng & Li Quantum Field Theory,Quantum Field Theory, RyderRyder Gauge Theories in Particle Physics,Gauge Theories in Particle Physics, Aitchison & Hey (Vols. 1 & 2)Aitchison & Hey (Vols. 1 & 2) Elementary Particle Physics: Concepts and PhenomenaElementary Particle Physics: Concepts and Phenomena Nachtmann Nachtmann

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1.1. Introduction Introduction

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The Standard ModelThe Standard Model

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gluon discovery at gluon discovery at ee++ee- - accelerator PETRAaccelerator PETRA(DESY, Hamburg)(DESY, Hamburg)

√√s=35s=35 GeV GeV

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discovery of Z boson at ppdiscovery of Z boson at pp accelerator SPSaccelerator SPS(CERN, Geneva)(CERN, Geneva)

1983, UA1 experiment, 1983, UA1 experiment, √√s=s=540 GeV540 GeV

Z bosonZ boson__

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Cross section Cross section σ(σ(ee++ee- - → Z → Z 00 → → f) f)

as function of as function of center of mass center of mass energy by OPAL energy by OPAL

(LEP)(LEP)

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Z mass distribution with calculations for 2, 3 and 4 Z mass distribution with calculations for 2, 3 and 4 neutrino types by all 4 experiments at LEPneutrino types by all 4 experiments at LEP

LEP experiments, LEP experiments, CERNCERN

Z Z →→ hadronshadrons

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Measurement of WMeasurement of W+ + WW- - at the threshold in eat the threshold in e+ + ee- -

interactions at LEP IIinteractions at LEP II

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Reconstructed W mass in 4 jet events by Reconstructed W mass in 4 jet events by ALEPH at LEP IIALEPH at LEP II

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mW = 80.401 ± 0.043 (stat) GeV

W mass measurements W mass measurements at the Tevatronat the Tevatron

±0.05%±0.05%

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Summary: W mass measurementsSummary: W mass measurements

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Particle accelerators used for precision Particle accelerators used for precision measurements for W and Z bosons measurements for W and Z bosons

/1960

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HERA: ep Collider and ExperimentsHERA: ep Collider and Experiments

√√s = 320 GeVs = 320 GeV QQ2 2 ≈≈100000 GeV100000 GeV22

λλCC ≈≈1010-3-3 fm fm

√√s = 320 GeVs = 320 GeV QQ2 2 ≈≈100000 GeV100000 GeV22

λλCC ≈≈1010-3-3 fm fm

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DIS – Neutral Current (NC)DIS – Neutral Current (NC)

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DIS - Charged Current (CC)DIS - Charged Current (CC)

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QCD fts to FQCD fts to F2 2 data using DGLAP equationsdata using DGLAP equations

sea sea quarks:quarks:

half of proton half of proton

momentummomentum

valence valence

quarks:quarks:

lead to lead to scaling scaling

violation, violation, FF

22(Q(Q22))≠const.≠const.

many many

gluonsgluons with small with small momentum momentum

fractionfraction

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____The Tevatron at FERMILAB: pp CollisionsThe Tevatron at FERMILAB: pp Collisions

Mai n I n jec tor & Recyc l er

Tevatron

Booster

p p

p source

Ch i cago

_

_

CDF DØ

60 km60 km

p

√s =1.96 TeV ∆t = 396 ns

Run I 1987 (92)-95Run I 1987 (92)-95Run II 2001-09: 40x larger dataset Run II 2001-09: 40x larger dataset at increased energyat increased energy

p _

top quark discoverytop quark discoverymeasure properties with high precisions:measure properties with high precisions:is it really the particle expected in SM?is it really the particle expected in SM?

__

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discovery of top quark at ppdiscovery of top quark at pp accelerator accelerator Tevatron (Fermilab, Batavia)Tevatron (Fermilab, Batavia)

__top quarktop quark

1995, CDF and D1995, CDF and DØØ experiments experiments, , √√s=1.8s=1.8 TeV TeV

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Top Quark Pair ProductionTop Quark Pair Production

tt gg

qq--

85%85%

qq tt

tt--

tt-- tt-- tt--

gg gg

gg gg gg

tt tt

15%15%

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Top Antitop SignaturesTop Antitop Signatures

all jetall jet40%40%

dilepton (e/dilepton (e/μ)μ) 5%5%

top decay:top decay: ~100% ~100%

reconstruct and identify:reconstruct and identify: electrons, muons, jets, electrons, muons, jets, b-jets and missing b-jets and missing transverse energy transverse energy

tt

bb

ℓℓ++ q'q'--

qq ν,ν,

,, WW++

dileptondilepton lepton + jetslepton + jets

lep

ton +

jets

lep

ton +

jets

l+jetsl+jets 35%35%

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Single Top Quark ProductionSingle Top Quark Production

s-channel:s-channel:

t-channel:t-channel:

missing Emissing ETT

isolated leptonisolated lepton

jetsjets

b-jetsb-jets

tt

VVtbtb

VVtbtb

frst direct measurement of |Vfrst direct measurement of |Vtbtb||

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Single Top Quark ObservationSingle Top Quark Observation

tt

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Single Top Quark ObservationSingle Top Quark Observation

|Vtb| = 1.07 ± 0.12 |V

tb| = 0.91 ± 0.11

5.05.0σσ

5.05.0σσ

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Single Top Quark ObservationSingle Top Quark Observation

1 year ago

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The Top Quark MassThe Top Quark Mass

free parameter in the Standard Modelfree parameter in the Standard Model

check the self-consistency of the Standard Model check the self-consistency of the Standard Model in combination with W mass measurementin combination with W mass measurement

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Tevatron Combination: Spring 2009Tevatron Combination: Spring 2009

mtop

= 173.1 ± 0.6 (stat) ± 1.1 (syst) GeV

world average:world average:

±0.75%±0.75%

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Top, W and Higgs Mass in the SMTop, W and Higgs Mass in the SM

mtop

= 173.1 ± 1.3 GeV

world average world average (March 2009)(March 2009)

Heinemeyer, Hollik, Heinemeyer, Hollik, Stockinger, Weber, Weiglein 2009Stockinger, Weber, Weiglein 2009

world average world average (March 2009)(March 2009)

mW = 80399 ± 23 MeV

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Search for the Higgs bosonSearch for the Higgs boson

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B factories Belle and BabarB factories Belle and Babar

ee++ee- - colliders PEP (SLAC) and KEKcolliders PEP (SLAC) and KEK

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The Large Hadron Collider (LHC)The Large Hadron Collider (LHC)

ATLASATLAS

CMSCMS

The Large Hadron Collider:The Large Hadron Collider: proton-proton collider proton-proton collider ⇨ ⇨ 2 separate beampipes2 separate beampipes 10 fb10 fb-1-1 per year per year high energy: high energy: √√s = 14 TeVs = 14 TeV 40 Mio. collisions per second40 Mio. collisions per second frst collisions in 2009frst collisions in 2009 4 experiments: 4 experiments: ATLASATLAS, CMS, ALICE, , CMS, ALICE, LHC-BLHC-B

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2.2. Quantum Quantum Electrodynamics, QEDElectrodynamics, QED

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2.32.3: The Feynman rules of QED: The Feynman rules of QED

2.2. Quantum Quantum Electrodynamics, QEDElectrodynamics, QED

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From O.Nachtmann,

From O.Nachtmann,

Elementary Particle Physics,

Elementary Particle Physics,

Springer, 1990

Springer, 1990

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3.43.4: Renormalisation in QED: Renormalisation in QED

3.3. Quantum Quantum Electrodynamics, QEDElectrodynamics, QED

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αα-1-1

QED QED as function of as function of √s√s in in ee++ee- - annihilationannihilation

αα-1-1

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4.4. Quantum QuantumChromodynamics, QCDChromodynamics, QCD

4.1 4.1 The Lagrange Density of QCDThe Lagrange Density of QCD

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Quark Flavours and ColourQuark Flavours and Colour

R= ee− hadrons ee−−

=3∑ quarkcharge2

12

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4.3 4.3 The Feynman Rules of QCDThe Feynman Rules of QCD

4.4. Quantum QuantumChromodynamics, QCDChromodynamics, QCD

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2 jet event at 2 jet event at ee++ee- - accelerator PETRAaccelerator PETRA

antiquarkantiquark

quarkquark

hadronshadrons

hadronshadrons

electronelectron positronpositron

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3 jet event and angular distribution 3 jet event and angular distribution at at ee++ee- - accelerator PETRAaccelerator PETRA

spin 0 spin 0 gluongluon

spin 1 spin 1 gluongluon

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4.4 4.4 Asymptotic FreedomAsymptotic Freedom

4.4. Quantum QuantumChromodynamics, QCDChromodynamics, QCD

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ααss

QQ22

strong coupling strong coupling ααss(Q(Q22))

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Noble Prize 2004 for running of strong coupling Noble Prize 2004 for running of strong coupling ααss

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World average World average (March 2009)(March 2009)

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4.5 4.5 ConfnementConfnement

4.4. Quantum QuantumChromodynamics, QCDChromodynamics, QCD

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Potential of strong quark interaction Potential of strong quark interaction from charmonium and bottomium datafrom charmonium and bottomium data

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Schematic HadronisationSchematic Hadronisation

quarkquark

antiquarkantiquark

pionspions

pionspions

quarkquark antiquarkantiquark

quark-antiquarkquark-antiquarkpairspairs

hadronshadrons

colour feld colour feld

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2 jet event at 2 jet event at ee++ee- - accelerator PETRAaccelerator PETRA

antiquarkantiquark

quarkquark

hadronshadrons

hadronshadrons

electronelectron positronpositron

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4.6 4.6 Quarkonium PhysicsQuarkonium Physics

4.4. Quantum QuantumChromodynamics, QCDChromodynamics, QCD

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Discovery of Discovery of J/ψ:J/ψ: pp- (Brookhaven) and epp- (Brookhaven) and e++e-scattering (SLAC)e-scattering (SLAC)

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ψ'(3.7) ψ'(3.7) →→ ψ(3.1) π ψ(3.1) π++ππ- - →→ e e++ee-- π π++ππ--

in a spark chamber detector in a spark chamber detector

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22 33SS 1 1 ((ψ'ψ'))

cccc__

energy levels for charmonium and positroniumenergy levels for charmonium and positronium

1133SS1 1

(J/ψ)(J/ψ)

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2233SS1 1 (ψ')(ψ')

cccc__

energy niveaux for charmonium and positroniumenergy niveaux for charmonium and positronium

1133SS1 1

(J/ψ)(J/ψ)

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4.4. Quantum Flavour Quantum FlavourDynamics, QFDDynamics, QFD

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(?)(?)Higgs-boson:Higgs-boson:explains massesexplains massesHH

±±

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Spontaneous Symmetry Breaking (SSB)Spontaneous Symmetry Breaking (SSB)

Higgs potential:Higgs potential:

Higgs ground state:Higgs ground state:

unmagnetised material:unmagnetised material:

ferromagnetic material:ferromagnetic material:SSBSSB

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From O.Nachtmann,From O.Nachtmann,Elementary Particle Elementary Particle Physics,Physics,Springer, 1990Springer, 1990

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Single Top Quark ProductionSingle Top Quark Production

s-channel:s-channel:

t-channel:t-channel:

missing Emissing ETT

isolated leptonisolated lepton

jetsjets

b-jetsb-jets

tt

VVtbtb

VVtbtb

frst direct measurement of |Vfrst direct measurement of |Vtbtb||

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Single Top Quark ObservationSingle Top Quark Observation

5.05.0σσ

5.05.0σσ

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First direct measurement of |VFirst direct measurement of |Vtbtb||

VVtbtb

assume: |assume: |VVtdtd||22 + | + |VV

tsts||22 « « ||VV

tbtb||22

assume: pure V-A and CP-conserving Wtb interactionassume: pure V-A and CP-conserving Wtb interaction

no assumption on quark families or CKM matrix unitarityno assumption on quark families or CKM matrix unitarity

before indirect limits: |Vbefore indirect limits: |Vtbtb| = 0.999127 | = 0.999127 ±± 0.00026 (10.00026 (1σ CLσ CL))

CKM Fitter Group for Beauty 2006CKM Fitter Group for Beauty 2006

|Vtb| = 0.88 ± 0.07 ++

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From O.Nachtmann,From O.Nachtmann,Elementary Particle Elementary Particle Physics,Physics,Springer, 1990Springer, 1990

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5.5. Higgs Physics Higgs Physics

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Fits to Electroweak Precision DataFits to Electroweak Precision Data

H H

H

LEP, SLD, TevatronLEP, SLD, Tevatron

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Bounds on SM Higgs MassBounds on SM Higgs Mass

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Branching Fractions of SM Higgs ParticleBranching Fractions of SM Higgs Particle

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Total Decay Width of SM Higgs ParticleTotal Decay Width of SM Higgs Particle

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cross

sec

tion (

pb

)cr

oss

sec

tion (

pb

)SM Higgs Production at the TevatronSM Higgs Production at the Tevatron

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Search for the Higgs bosonSearch for the Higgs boson