niels tuning (1) “elementary particles” lecture 5 niels tuning harry van der graaf

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Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

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Page 1: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Niels Tuning (1)

“Elementary Particles”Lecture 5

Niels Tuning

Harry van der Graaf

Page 2: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Thanks

• Ik ben schatplichtig aan:– Dr. Ivo van Vulpen (UvA)

– Prof. dr. ir. Bob van Eijk (UT)

– Prof. dr. Marcel Merk (VU)

Niels Tuning (2)

Page 3: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Homework

Page 4: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Exercises Lecture 4:

Niels Tuning (4)

1

Page 5: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Exercises Lecture 4:

Niels Tuning (5)

Page 6: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Exercises Lecture 4:

Niels Tuning (6)

Page 7: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Exercises Lecture 4:

Niels Tuning (7)

Page 8: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Plan

1) Intro: Standard Model & Relativity

2) Basis

1) Atom model, strong and weak force

2) Scattering theory

3) Hadrons

1) Isospin, strangeness

2) Quark model, GIM

4) Standard Model

1) QED

2) Parity, neutrinos, weak inteaction

3) QCD

6) e+e- and DIS

7) Higgs and CKM

Niels Tuning (8)

1900-1940

1945-1965

1965-1975

1975-2000

2000-2015

17 Feb

3 Mar

17 Mar

19 May

26 May

10 Feb

21 Apr

Page 9: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Summary Lects. 1-5

Page 10: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Theory of relativity– Lorentz transformations (“boost”)

– Calculate energy in collissions

• 4-vector calculus

• High energies needed to make (new) particles

Lecture 1: Relativity

Niels Tuning (10)

Page 11: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• 4-vectors: – Space-time x

– Energie-momentum p

– 4-potential A

– Derivative ∂

– Covariant derivative D

– Gamma matrices

• Tensors– Metric g

– Electromagnetic tensor F

Lecture 1: 4-vector examples

Niels Tuning (11)

Page 12: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Schrödinger equation– Time-dependence of wave function

• Klein-Gordon equation– Relativistic equation of motion of scalar particles

Dirac equation– Relativistically correct, and linear

– Equation of motion for spin-1/2 particles

– Described by 4-component spinors

– Prediction of anti-matter

Lecture 2: Quantum Mechanics & Scattering

Niels Tuning (12)

Page 13: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Scattering Theory– (Relative) probability for certain process to happen

– Cross section

• Fermi’s Golden Rule

– Decay: “decay width” Γ

– Scattering: “cross section” σ

Lecture 2: Quantum Mechanics & Scattering

Niels Tuning (13)

ClassicClassic Scattering amplitude Scattering amplitude inQuantum Field Theory

a → b + c

a + b → c + d

Page 14: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• “Partice Zoo” not elegant

• Hadrons consist of quarks

Observed symmetries– Same mass of hadrons: isospin

– Slow decay of K, Λ: strangeness

– Fermi-Dirac statistics Δ++, Ω: color

• Combining/decaying particles with (iso)spin– Clebsch-Gordan coefficients

Lecture 3: Quarkmodel & Isospin

Niels Tuning (14)

Page 15: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Arbitrary “gauge” Physics invariant

Introduce “gauge” fields in derivative

Interactions!

• QED

• Weak interactions

• QCD

Lecture 4: Gauge symmetry and Interactions

Niels Tuning (15)

2

exp8,1

aaa x

i

1 photon

3 weak bosons

8 gluons

Page 16: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

EM coupling α

Strong coupling αS

Confinement

Asymptotic freedom

Lecture 5: Running couplings

Niels Tuning (16)

Page 17: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Feynman rules: Example

Niels Tuning (17)

• Process: e-μ- →μ- e-

Remember the 4-componentspinors in Dirac-space:

Page 18: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• spin-0 particles (Klein-Gordon)

• spin-1/2 fermions (Dirac)

• Photons

Lagrangian Equation of motion

Niels Tuning (18)

Klein-Gordon equation

Dirac equation

Maxwell equations

Page 19: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

1) Assume symmetry ψ→ψ’= ψeiα(x)

2) Keep Eqs valid

Covariant derivative

Gauge Invariance

Niels Tuning (19)

1) Arbitrary gauge

2) Keep Eqs valid

This implies: ψ→ψ’= ψeiα

We started globally:

Then we went local:

AAA

iqAD

Page 20: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Quantum Electro Dynamics - QED

Niels Tuning (20)

Fermion ψ with mass mInteraction with coupling q Photon field Aμ

m qγμ

Page 21: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

QCD Lagrangian

Niels Tuning (21)

Fermion ψ with mass mInteraction with coupling q 8 Gluon fields Aμ

m

Self-interaction

qγμ

Page 22: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Local SU(3) gauge transformation

• Introduce 8 Aμa gauge fields

• Non-“Abelian” theory,

• Self-interacting gluons– Gluons have (color) charge

• Different “running”

• Local U(1) gauge transformation

• Introduce 1 Aμ gauge field

• “Abelian” theory,

• No self-interacting photon– Photons do not have (electric) charge

• Different “running”

QED QCDQED QCD

Niels Tuning (22)

2

exp8,1

aaa x

i

QED and QCD

Page 23: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

1) e+e- scattering e+e- →μ+μ-

e+e- →cc Discovery of charm and colour (quantity “R”)

e+e- →qq g Discovery of the gluon

e+e- →Z 3 neutrino’s

e+e- →WW

• Deep Inelastic Scattering (DIS) (lepton-proton scattering) Quarkmodel: do quarks exist??

Sub-structure

Bjorken-x, sum rules

Scaling (violations)

‘Parton density functions’ (pdf) and ‘structure functions’

Outline for today:

Niels Tuning (23)

Page 24: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+e- Scattering

Page 25: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• e+e-→μ+μ-

• e+e-→cc– Confirmation of “color”

– Discovery of charm

• e+e-→qq g– Discovery of the gluon

• e+e-→tt– Hunt for the top

• e+e-→Z– 3 neutrino’s

• e+e-→WW

Shopping list

Niels Tuning (25)

Page 26: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+e- colliders

Niels Tuning (26)

Accelerator Lab s (GeV) Year

SPEAR SLAC 2 – 8 1972 - 1990

DORIS I, II DESY 10 1974 - 1993

CESR(-c) Cornell 3.5 - 12 1979 - 2008

PEP SLAC 20 - 29 1980 - 1990

PETRA DESY 12 – 47 1978 - 1988

TRISTAN KEK 50 – 60 1987 - 1995

SLC SLAC 90 1988 - 1998

LEP I, II CERN 90 – 208 1989 - 2000

Page 27: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Examples of e+e- processes

time

Page 28: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Examples of e+e- processes

Page 29: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Rutherford scattering

(scattering off static point charge)

• Mott scattering

(now with high energy, taking into account recoil of target and magnetic moment: spin ½)

• spin-½ spin-½ scattering

(average over incoming spin, sum over outgoing spin)

Scattering

Niels Tuning (29)

Page 30: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Point cross section

• At √s=10 GeV:

σ(e+e-→μ+μ-) ~ 0.9 nb

e+e-→μ+μ-

Niels Tuning (30)

Page 31: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+e-→hadrons

• Point cross section

• At √s=10 GeV:

σ(e+e-→q+q-) ~ 3.6 nb

Page 32: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+

e- γ f

f-

e+e-→hadrons

• Compare cross section of σ(e+e-→q+q-) to σ(e+e-→μ+μ-)

Photon couples to fermion charge!

Color of quarks?

Inspect Ratio R:

...222 sduc qqqNR

Page 33: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

muons

quarks

Prediction R: me+e- < 2mc

Without color: R = 2/3

R (ee qq )

(ee )

(2 /3)2 (1/3)2 (1/3)2

12 2

3

R (ee qq )

(ee )

3(2 /3)2 3(1/3)2 3(1/3)2

12 2 With 3 colors: R = 2

Page 34: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

muons

quarks

Without color: R = 10/9

R (ee qq )

(ee )

(2 /3)2 (1/3)2 (1/3)2 (2 /3)2

12 10

9

R (ee qq )

(ee )

3(2 /3)2 3(1/3)2 3(1/3)2 3(2 /3)2

12 30

9With 3 colors: R = 30/9

Prediction R: me+e- > 2mc

Page 35: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

me+e- (GeV)

1 (3) colors

1.1(3.3)

0.7 (2)

prediction

1

0

No color (udsc)No color (uds)

with color(udsc)

data

With color (uds)

Page 36: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+

e- γ f

f-

e+e-→hadrons

So, quarks have color!

How about spin?

Page 37: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Sam ‘J’ Ting. Burt ‘’ Richter

Discovery of charm (J/November 1976: ‘November revolution’New meson discovered (J/ψ) with mass 3.16 GeVQuark model: J/ψ consists of pair of c-quarks

e+e-→cc

Page 38: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Sam ‘J’ Ting. Burt ‘’ Richter

Discovery of charm (J/November 1976: ‘November revolution’New meson discovered (J/ψ) with mass 3.16 GeVQuark model: J/ψ consists of pair of c-quarks

e+e-→cc

Because of the nearly simultaneous discovery, the J/ψ is the only elementary particle to have a two-letter name. Richter named it "SP", after the SPEAR accelerator used at SLAC; however, none of his coworkers liked that name. After consulting with Greek-born Leo Resvanis to see which Greek letters were still available, and rejecting "iota" because its name implies insignificance, Richter chose "psi" – a name which, as Gerson Goldhaber pointed out, contains the original name "SP", but in reverse order.[2] Coincidentally, later spark chamber pictures often resembled the psi shape. Ting assigned the name "J" to it, which is one letter removed from "K", the name of the already-known strange meson; possibly by coincidence, "J" strongly resembles the Chinese character for Ting's name ( 丁 ). J is also the first letter of Ting's oldest daughter's name, Jeanne.

Page 39: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

1970: Prediction of charm quark Observation K0→μμ

Lesson:Loop diagrams are sensitive to heavy particles

Intermezzo: “indirect discoveries”

GIM, Phys.Rev.D2,1285,1970

s d

μ

μ

“Loop” diagram:

Page 40: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+e-→qq g

Niels Tuning (40)

From: arXiv:1008.1869

1979

Page 41: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

J/ψ

c e-

e+

γ

e+e-→cc

c

Page 42: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

b e-

e+b

γ

e+e-→bb ?

• In modern times: yes!• Babar experiment at SLAC (USA)

• Belle experiment at KEK (Japan)

• e+e-→Υ(4S) → B0B0

• M(Υ(4S)) =10579.4 MeV

• 2 x M(B0) = 10559.2 MeV (coincidence??)

“B-factories”

Y

Page 43: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Intermezzo: bottom discovery

Niels Tuning (43)

• Fermilab (Chicago), 400 GeV proton – fixed target– p + (Cu,Pt) μ+ + μ- + anything

– m(bb)~9.5 GeV , so m(b)~5 GeVm(b)~5 GeV

“background subtracted”:

Page 44: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+e-→ttt e-

e+

γ

e+e- cross-section

t

• 1977: bottom discovered

• How heavy could the toptop be??

– 20 GeV ?

– 25 GeV ??

– 30 GeV ???

– Built Tristan accelerator, with Topaz detector (Japan)

– Reached 25.5 GeV in 1986

At minimum of cross section…

Page 45: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+e-→ttt e-

e+

γ

e+e- cross-section

t

• 1977: bottom discovered

• How heavy could the toptop be??

– 20 GeV ?

– 25 GeV ??

– 30 GeV ???

– Built Tristan accelerator, with Topaz detector (Japan)

– Reached 25.5 GeV in 1986

At minimum of cross section…

Page 46: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

ARGUS almost discovered the top quark: mtop> 50 GeV

Lesson:Loop diagrams are sensitive to heavy particles

Intermezzo: “indirect discoveries”

ARGUS Coll, Phys.Lett.B192:245,1987

?

bs

s

b

Page 47: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Z-boson

f e-

e+ anti-f

Z

e+e-→Z(From: PDG)

Page 48: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Remember:

• AB+C : Total decay rate

• τ = ħ /Γ

• A+B R C+D: Resonance:

e+e-→Z

Breit-Wigner

E0-Γ/2 E0 E0-Γ/2

Pmax

Pmax/2

Page 49: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

3 families !

e+e-→Z

• Measure total width, with energy scan: “Z-lineshape” Total width is sum of “partial widths”

• Measure branching ratios of Zqq and Zl+l-

“Invisible width” due to neutrinos

..., eetotalZ

Page 50: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+e-→WW

• Upgrade of LEP:

90 208 GeV!

• Enough energy to create WW-pairs

and ZH-pairs?!

Page 51: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

e+e-→WW

(a) (b) (c)

(c)

(a+c)

(a+b+c)

• Triumph for Standard Model:

Page 52: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Intermezzo:Discovery Z and W

Page 53: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Gargamelle experiment

Neutrinos on target (12,000 liter freon (CF3Br)

Discovery neutral currentDiscovery neutral current

υμ υμ

Z

quark(nucleon)

quark(hadrons)

19731973

Page 54: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Spokesman UA1 experiment In 1989 Director General CERN Initiator of Energy Amplifier

SPS proton-anti-protoncollider √s = 540 GeV Carlo RubbiaSimon van der Meer

Correcting signal

stochastic cooling

Direct observation weak-force carrierDirect observation weak-force carrier

Page 55: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Discovery Z-bosonDiscovery Z-boson

“Experimental observation of lepton pairs of invariant mass around 95 GeV/c2

at the CERN SPS collider”

Nederlands tintje

Ml+l- [GeV/c2]

Lepton pair mass (4 events)

3 June 19833 June 1983

Page 56: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

24 februari 198324 februari 1983

Discovery W-bosonDiscovery W-boson

Prediction:

Observation:

2012:

“Experimental observation of isolated large transverse energy electrons with associated

missing energy at √s=540 GeV”

Page 57: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Deep Inelastic Scattering

Lepton – proton scatteringor:

Hitting something big, using something small

Page 58: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Quarkmodel: do quarks exist??

• Substructure

• Bjorken-x, sum rules

• Scaling

• ‘Parton density functions’ (pdf) and ‘structure functions’

• Scaling violations

Shopping list

Niels Tuning (58)

Page 59: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Scattering

Niels Tuning (59)

• Rutherford scattering

(scattering off static point charge)

• e+e-→μ+μ- scattering

(s-channel)

• e-μ+→e-μ+ scattering

(t-channel)

Page 60: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Point cross section

e+q→e+q

Niels Tuning (60)

e+ e+

q q

2sin

)cos1(2

2

22

y

EQ e

Page 61: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• Easiest: fixed target

– ep scattering

– μp scattering

– νp scattering

• 1990’s: ep collider

DIS experiments

Niels Tuning (61)

protonsprotons

electronselectrons

Experiment Accel Lab lepton Elep Ehad Year

SLAC-MIT SLAC e 20 fixed 1967-1973

Gargamelle CERN fixed

E80 - SLC SLAC fixed

CHORUS SPS CERN 10-200 fixed 1998

CCFR Tevatron Fermilab 30-360 fixed

NMC SPS CERN 90-280 fixed 1986-1989

EMC/SMC SPS CERN 100-190 fixed 1984-1994

BCDMS SPS CERN 100-280 fixed

ZEUS, H1 HERA DESY e 27.5 920 1992-2007

NB: Table not complete

Page 62: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

electron protonbeam target

detector

Robert Hofstadter

spin ½, r=10 -15m

spin 0

spin ½, point

Page 63: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Sub-structure

Niels Tuning (63)

• Remember Rutherford

– Back-scatter of α from nucleus

• Now:

– Back-scatter of e from quarks

Page 64: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

data

voorspelling

electron protonbeam target

detector

Page 65: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

J.D. Bjorken “scaling hypothesis” (1967):

• If scattering is caused by pointlike constituents structure functions must be independent of Q2

Would you expect a Q2 dependence?

R. Feynmans “parton model” (1969):

• Proton consists of ‘constituents’

• “Physicists were reluctant to identify these objects with quarks at the time, instead calling them "partons" – a term coined by Richard Feynman.”

Scaling

Niels Tuning (65)

Page 66: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton

valence quarks

sea quarksQCD: deep in the protonQCD: deep in the proton

Page 67: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton

valence quarks

sea quarksQCD: deep in the protonQCD: deep in the proton

Two important variables:

• Q2: 4-mom. transfer, scale

• x: fractional momentum of quark

Page 68: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• eq scattering:

• ep scattering:

Deep Inelastic Scattering

Niels Tuning (68)

(Fro

m: P

hD th

esis

N.T

unin

g)

Form factor

Page 69: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• ep scattering:

• F2(x): proton structure function

• q(x): parton density function

Deep Inelastic Scattering

Niels Tuning (69)

Page 70: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

• ep scattering:

• F2(x): proton structure function

• q(x): parton density function

But… the proton had 3 quarks?!

Sum rules:

Parton Densities

Niels Tuning (70)

Page 71: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton: xProton: x

• What is ‘momentum fraction’ distribution of quarks??

• Quarks:

“Valence”

“Sea”

(From: Halzen & Martin)

Page 72: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton: xProton: x

• What is ‘momentum fraction’ distribution of quarks??

• Quarks:

“Valence”

“Sea”

Dynamic, QCD !

(From: Halzen & Martin)

Page 73: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton: xProton: x

(From: Halzen & Martin)

(From: PhD thesis N.Tuning)

• What is ‘momentum fraction’ distribution of quarks??

• Quarks:

“Valence”

“Sea”

Dynamic, QCD !

x=1/3

Page 74: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton: Q2Proton: Q2

• The “deeper” one looks into the proton, the more quarks and gluons

Page 75: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton: x, Q2Proton: x, Q2

(From: PhD thesis N.Tuning)

Page 76: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton: x, Q2Proton: x, Q2

(From: PhD thesis N.Tuning)

• The “deeper” one looks into the proton, the more quarks and gluons

• “QCD evolution”

• Describes quark-gluon splitting

DGLAP evolution eqs:

Page 77: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

J.D. Bjorken “scaling hypothesis” (1967):

• If scattering is caused by pointlike constituents structure functions must be independent of Q2

• Would you expect a Q2 dependence?

Yes, due to QCD, ie. quark/gluon splitting ! Matured in mid ‘70s

The proton is “dynamic” !

Measurement of F2(x,Q2) very accurate test of QCD

Scaling violations

Niels Tuning (77)

Page 78: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Scaling violations

Niels Tuning (78)

Measurement of F2(x,Q2) very accurate test of QCD

Page 79: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton StructureProton Structure

45

The deeper you look, the more low-x quarks

Page 80: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton StructureProton Structure

45

The deeper you look, the more low-x quarks

Page 81: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton StructureProton Structure

Page 82: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Proton Structure: knowledge needed for predictionsProton Structure: knowledge needed for predictions

Page 83: Niels Tuning (1) “Elementary Particles” Lecture 5 Niels Tuning Harry van der Graaf

Plan

1) Intro: Standard Model & Relativity

2) Basis

1) Atom model, strong and weak force

2) Scattering theory

3) Hadrons

1) Isospin, strangeness

2) Quark model, GIM

4) Standard Model

1) QED

2) Parity, neutrinos, weak inteaction

3) QCD

6) e+e- and DIS

7) Higgs and CKM

Niels Tuning (83)

1900-1940

1945-1965

1965-1975

1975-2000

2000-2015

17 Feb

3 Mar

17 Mar

19 May

26 May

10 Feb

21 Apr