Studiedag Natuurkunde en Sterrenkunde
Feb. 10, 2005
http://www.wyp2005.nl
The Standard Model of
Particle Physics
Piet Mulders
http://www.nat.vu.nl/~mulders
mulders@few.vu.nl
The Standard Model of particle physics
•
•
•
•
•
•
•
The particle content
Experiments; matter and antimatter
The fundamental forces
Force carriers
Central theme of Standard Model: symmetry
The history of the universe
Remaining questions in the standard model
• Mass and structure of space-time
• The mass in the universe
• Neutrinos
The particle content
Theory
Experiment
Application
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
Materie
MATTER
A bit more or less
Hydrogen in metals
like Yttrium-Palladium
TRANSPARENT
(Griessen)
REFLECTING
Materie
MATTER
ATOM
10-10 m
ELECTRON
The periodic table
Materie
MATTER
ELECTRON
ATOM
10-10 m
NUCLEUS
10-14 m
NUCLEON
proton/neutron
10-15 m
NEUTRINO
Atomic nuclei
Island of
stability
Atomic nuclei
• Isotopes
• Radioactivity
alpha
beta
gamma
after 15 min.
Neutrinos
more on neutrinos
Building blocks of
the subatomic world
Materie
MATTER
ELECTRON
ATOM
10-10 m
NUCLEUS
10-14 m
NUCLEON
proton/neutron
10-15 m
NEUTRINO
QUARK
up/down
Basic building
blocks of matter
home
How do we
know this?
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
By using the largest microscopes on Earth
Antiparticles
Standard model content
• 3 particle families
The fundamental forces
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
Forces in daily life


Electromagnetism
Gravity
• Two of four basic forces
• Both based on fundamental principles
Standard model
• 3 particle families
• 4 fundamental forces
• strong force
quark  nucleon  atomic nucleus
• electromagnetic force
atom  molecule  complexity
• weak force
decay
• gravity
more on gravity
Standard model
• 3 particle families
• 4 fundamental forces
• Corresponding force particles
And a consistent
theoretical framework:
a renormalizable nonabelian gauge theory
Steven Weinberg
Sheldon Glashow
Abdus Salam
Gerard ‘t Hooft
Martinus Veltman
How is the action of
force particles
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
Force carriers of weak interactions
Force particles play a role in:
 Interactions
 Pair creation
 Annihilation
Example: neutron decay
Neutron beta-decay
n

p + e- + ne
At the quark level
d

u + e- + ne
Z0 decay into:
 quark pairs
(except top quarks!)
 lepton pairs
 e+e-, m+m-, t+t neutrino pairs
(‘invisible’)
lifetime is inverse of
decay probability 1/t = G
G = S Gi
collission probability
Three kinds of neutrinos!
energy (GeV)
Strength of
interactions
strong
electromagnetic
weak
GF ~ a/MW2
How do quarks and gluons give the
proton its properties?
Massless quarks
and gluons
A one-line theory:
QCD
Protons and neutrons:
Basic constituents of
atomic nuclei forming
99.5 % of the visible
mass in the universe
QED versus QCD
This implies a
constant force
T0 = 1 GeV/fm
= 20 Ton
Frank Wilczek
David Gross
David Politzer
short
distances
large
distances
Permanent
confinement of
colored quarks
Mass of nucleon
• Almost massless quarks: mu ~ 5 MeV and md ~ 10 MeV
• constant force T0 = 1 GeV/fm leads to confinement
of color over distances of ~ 0.8 fm
Pressure in bubble: B ~ 100 MeV/fm3
 EV = 4pBR3/3 ~ 200 MeV
u
u
proton
• Momentum p ~ 1/R ~ 250 MeV
• Energy per quark: EQ ~ 250 MeV
• Total energy: E ~ 940 MeV = mass of nucleon
d
u
d
d
neutron
Phase diagram of QCD
T
quark-gluon plasma
hadrons
d
nuclear matter
m
u
A model calculation
T (MeV)
Harmen Warringa
Daniël Boer
mq (MeV)
Central theme of
standard model:
SYMMETRY
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
Mirror symmetry
•
•
•
•
Mirror world?
Example: top
Mirror world exist
Conclusion: mirror symmetry is a
symmetry of our daily world
Broken
mirror symmetry
For neutrinos there exist
nL but not nR
lefthanded
• A pion decays into spinning
particles
• For a neutrino only one spin
direction exist!
• But how can we measure this?
• spin + charge  magnet
• Only m+ observed at N-pole of
the magnet!
mirror images
righthanded
CP symmetry
• Mirror symmetry (P) is broken in the subatomic world
• Particle-antiparticle symmetry (C) is also broken
• But … the combination is indeed
almosta symmetry
_ _
_
K0 = ds, K0 = sd have slightly different masses and decay in a different way
CPT symmetry
Time reversal
• CPT is (to our present knowledge!) indeed a good
symmetry of the world
• CP is almost a good symmetry
• Thus also time reversal is almost a good symmetry, but
not exact!
• This symmetry breaking allows for the surplus of
matter over antimatter in the universe
(even if this is only 1 : 109)
Number of baryons  0,25 x 1079 (~ 0,25 per m3)
But the number of photons and neutrinos  1088 (~ 400 per cm3)
more on mass in universe
CP-violation in standard model
CP-violation can be implemented in the standard model
through complex phase(s) in CKM-matrix.
This requires at least three families!
Cabibbo
Kobayashi
Maskawa
The history of the universe
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
13.7 billion years ago
BIG BANG
inflation
and finally now….
Remaining questions in the
standard model
•
•
•
•

3 particle families
(Anti)matter forces
4 fundamental
in universe ??
corresponding
force particles
Black holes ?
Glimp of the ‘Higgs particle(s)’?
… and very many questions
http://www.nat.vu.nl/~mulders
Why 3
families ??
Space and time ?
Points ?
Strings ?
remaining!
P.J. Mulders
home
Where to find the answers?
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
In accelerators ?
• Collissions in the Large
Hadron Collider at CERN
– New particles
(Higgs, …)
– New symmetries
(Fermion-Boson symmetry)
– Origin of mass
– Origin of symmetry
breaking (e.g. CP-violation)
(future) detectors at CERN
CMS
LHCb
ATLAS
Super Kamiokande
Underground ?
Underground ?
• Atmospheric neutrinos oscillate
over thousands of kilometers
• Solar neutrinos change flavor
in the Sun
• Masses mn ~ 0.01 eV
(that is extremely small, but
compare k ~ 10-4 eV/K)
Sudbury Neutrino Observatory (SNO)
In the mediterranean?
or the ice?
• Looking for high energy
cosmic neutrinos
– Supernovae
– Neutron stars
– Black holes
ANTARES
AMANDA
Answers in the sky?
Dark Energy
73%
23%
Cosmic
Accelaration
Cold Dark
Matter
Dark baryonic
matter (3.5%)
Normal matter: stars (0.4%)
Cosmic microwave background
WMAP satellite
Angular Power Spectrum
T  ,  
2.7248K
2.7252K
T  ,   =  almYlm  ,  
=
N baryons
N photons
-10
= (6.5+-0.4
)

10
0.3
EINDE
home
Mass and the structure
of space-time
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
Mass: energy and momentum
If v much smaller than c
E=
mc 2
p=
mv
1-
v2
c2
1 - vc2
2
E  mc 2 + 12 mv 2
p  mv
Velocity of light: c = 3 x 108 m/s = 300 000 km/s
Mass: gravity
zware
trage
massa = massa
2
Mm
v
G 2 =m
R
R
zwaartekracht
versnelling ac
bij cirkelbeweging
rotatiesnelheden in galaxies
GM ( R)
v( R) =
R
omloopstijden en afstanden
(planeten, dubbelsterren)
T
4p
=
3
R
GM
2
2
Mass: curvature of space-time
• Zonder kracht:
rechtlijnige beweging
• Zwaartekracht wordt
veroorzaakt door
massa
• Massa bepaalt ook
mate van respons
(equivalentieprincipe)
GEEN KROMMING
POSITIEVE KROMMING
NEGATIEVE KROMMING
Algemene relativiteitstheorie:
Beweging in zwaartekrachtveld is
rechtlijnige beweging in een t.g.v
massa gekromde ruimte
curvature
• Kromming van een bol: k = 1/R2
• Bijv voor voetbal: k = 50 /m2
• Bijv voor aarde: k = 2.8 x 10-14 /m2
• Andere methode gaat via hoeken
k = a/S(a)
The boomerang experiment
• 2 terra-cruisers
• back and forth!
space-time
curvature
Vergelijk met ‘bol’:
pR = 42 min
= 7.5 x 1011 m
of
 a = 20 m/s
= 0.67 x 10-7
 R = (16 km)/a
= 2.4 x 1011 m

1 s = 3 x 108 m
k = 1/R2 = 1.6 x 10-23/m2 !!!
home
The matter in the universe
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
Matter in the universe
Dark Energy
73%
23%
Cosmic
Accelaration
Cold Dark
Matter
Dark baryonic
matter (3.5%)
Normal matter: stars (0.4%)
Evidence for Dark Matter
Rotation of galaxies
Gravitational lenses
Microwave background
Ultra High Energy Cosmic Rays
Data beyond
the GZK limit:
new physics?
protons only
2
-2
-1
-1
eV m s sr )
10
3
(E)  E (10
24
1
uniform distribution, a = 
0,1
AGASA data (E - 20%)
E
HiRes 1 Monocular
18
18,5
19
19,5
log E (eV)
10
pion
20
E’
20,5
CMB
Neutrinos
http://www.nat.vu.nl/~mulders
P.J. Mulders
home
Origin of neutrinos
• Weak decay of atomic nuclei (Sun/reactors):
…n…  …p… + e- + ne (righthanded antineutrino)
…p…  …n… + e+ + ne (lefthanded neutrino)
• Cosmic rays (decay of the pion)
p-  m- + nm
(righthanded antineutrino)
p+  m+ + nm
(lefthanded neutrino)
• Remnants of the big bang
just as photons (T = 2.7 K background) for all three kinds
of neutrinos (ne, nm en nt) about 400 per cm3
Questions around neutrinos
• What are the
masses of neutrinos
• Where are the
neutrinos from the
Sun?
Half of them is
missing!
How to detect neutrinos?
Neutrino detectors
Sudbury Neutrino Observatory
(SNO)
Neutrino detection techniques
Detection via cherenkov
light emitted by particles
moving “faster” than light
(from antares experiment)
Neutrino detectors
Super Kamiokande
Neutrino oscillations in
the atmosphere
• Neutrinos in the atmosphere are created
in the decay of pions. These are mainly
nm neutrinos
• If the nm neutrino is a
quantummechanical
Place and time
superposition of two
of production
neutrinos n1 en n2 it
gives rise to oscillations
Place and time
of measurement
Neutrino oscillaties in atmosfeer
• Superkamiokande
showed oscillations
depending on the
distance L to the
detector
• Oscillation-wavelength
is thousands of
kilometers  mass
smaller than 0.000 001
of that of the electron
• Nature of oscillations
is nm  nt
Consequences of n mass
• Particles with mass must
come as righthanded and
lefthanded!
• This is only possible if the
neutrino is its own antiparticle (as the photon,
but unlike the electron)
Dirac and Majorana neutrinos
Fermion
(general)
P = spiegelen
C = deeltje-antideeltje
T = tijdomkeer
Dirac and Majorana neutrinos
Dirac
neutrino
Dirac and Majorana neutrinos
Majorana
neutrino
Neutrino oscillations in the Sun
• Oscillations arise because the interaction of ne with
matter differs from the interaction of nm
(ne ‘feels’ electrons, nm doesn’t!)
• SNO showed that what is missing on ne appears as a
different kind of neutrino
• Most probably these are oscillations of the type ne  nm
Neutrino mixing
Mixing pattern of neutrinos as for
quarks with possibly also complex
phases and CP violation