the standard model of particle physics piet mulders [email protected] mulders studiedag natuurkunde...
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The Standard Model of Particle Physics
Piet Mulders
http://www.nat.vu.nl/~mulders
http://www.wyp2005.nl
Studiedag Natuurkunde en SterrenkundeFeb. 10, 2005
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
Materie
MATTER
A bit more or less Hydrogen in metals like Yttrium-Palladium (Griessen)
REFLECTING
TRANSPARENT
Materie
MATTER
ELECTRONATOM10-10 m
MATTER
ELECTRONATOM10-10 m
NUCLEUS10-14 m
NEUTRINO
ATOM10-10 m
ELECTRON
MATTER
NUCLEUS10-14 m
NEUTRINO
NUCLEONproton/neutron10-15 m
Materie
ELECTRON
MATTER
ATOM10-10 m
NUCLEUS10-14 m
NEUTRINO
NUCLEONproton/neutron10-15 m
ELECTRON
MATTER
ATOM10-10 m
NUCLEUS10-14 m
NEUTRINO
NUCLEONproton/neutron10-15 m
QUARKup/down
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
UNIFICATION
more on gravity
Standard model
• 3 particle families• 4 fundamental forces• Corresponding force particles
And a consistent theoretical framework: a renormalizable non-abelian gauge theory
Steven WeinbergSheldon GlashowAbdus Salam
Gerard ‘t HooftMartinus Veltman
Force carriers of weak interactions
Force particles play a role in:
Interactions Pair creation Annihilation
Three kinds of neutrinos!
Z0 decay into: quark pairs (except top quarks!) lepton pairs
ee, , neutrino pairs (‘invisible’)
lifetime is inverse of decay probability
i
colli
ssio
n p
robabili
ty
energy (GeV)
How do quarks and gluons give the proton its properties?
A one-line theory: QCDMassless quarks
and gluons
Protons and neutrons:Basic constituents of atomic nuclei forming99.5 % of the visible mass in the universe
QED versus QCD
This implies a constant force T0 = 1 GeV/fm = 20 Ton
Permanent confinement of colored quarks
short distances
large distances
Frank WilczekDavid GrossDavid Politzer
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 fmPressure in bubble: B ~ 100 MeV/fm3 EV = 4BR3/3 ~ 200 MeV
• Momentum p ~ 1/R ~ 250 MeV
• Energy per quark: EQ ~ 250 MeV
• Total energy: E ~ 940 MeV = mass of nucleon
d uu
u d d
proton
neutron
Mirror symmetry
• Mirror world?• Example: top• Mirror world exist• Conclusion: mirror symmetry is a
symmetry of our daily world
Broken mirror symmetry
• A pion decays into spinning particles
• For a neutrino only one spin direction exist!
• But how can we measure this?
• spin + charge magnet
• Only observed at N-pole of the magnet!
lefthanded
For neutrinos there exist L but not R
mirror imagesrighthanded
CP symmetry
• Mirror symmetry (P) is broken in the subatomic world• Particle-antiparticle symmetry (C) is also broken• But … the combination is indeed a symmetryalmost
__ _K0 = ds, K0 = sd have slightly different masses and decay in a different way
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!
CabibboKobayashiMaskawa
Remaining questions in the standard model
• 3 particle families• 4 fundamental forces• corresponding force particles• Glimp of the ‘Higgs particle(s)’?
… and very many questions remaining!
(Anti)matter in universe ??Black holes ?
Space and time ?Points ?Strings ?
Chaos ?
Phase tr
ansitions ?
Complexity
Hadrons Why 3 families ??
Neutrinos ?
Their masses ?
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)
Underground ?
• Atmospheric neutrinos oscillate over thousands of kilometers
• Solar neutrinos change flavor in the Sun
• Masses m ~ 0.01 eV
(that is extremely small, but compare k ~ 104 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?
Cold Dark Matter
Dark baryonicmatter (3.5%)
Normal matter: stars (0.4%)
Dark Energy
CosmicAccelaration
73%
23%
, ,lm lmaT Y
WMAP satellite
,T 2.7248K 2.7252KAngular Power Spectrum
l
0.4 100.3(6.5 ) 10baryons
photons
N
N
Cosmic microwave background
Mass: energy and momentum
Velocity of light: c = 3 x 108 m/s = 300 000 km/s
2
2
2
1 vc
mcE
2
21 vc
mvp
2 212E mc mv
p mv
If v much smaller than c
Mass: gravity
( )( )
GM Rv R
R
rotatiesnelheden in galaxies
2 2
3
4T
R GM
omloopstijden en afstanden(planeten, dubbelsterren)
2
2
Mm vG mR R
zwaartekrachtversnelling ac
bij cirkelbeweging
zwaremassa
tragemassa=
Mass: curvature of space-time
• Zonder kracht: rechtlijnige beweging
• Zwaartekracht wordt veroorzaakt door massa
• Massa bepaalt ook mate van respons (equivalentieprincipe)
Algemene relativiteitstheorie:Beweging in zwaartekrachtveld is rechtlijnige beweging in een t.g.v massa gekromde ruimte
GEEN KROMMING POSITIEVE KROMMING NEGATIEVE KROMMING
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 = /S()
R = 42 min = 7.5 x 1011 mof = 20 m/s = 0.67 x 10-7
R = (16 km)/ = 2.4 x 1011 m k = 1/R2 = 1.6 x 10-23/m2 !!!
Vergelijk met ‘bol’:
space-time curvature
home
1 s = 3 x 108 m
Matter in the universe
Cold Dark Matter
Dark baryonicmatter (3.5%)
Normal matter: stars (0.4%)
Dark Energy
CosmicAccelaration
73%
23%
Ultra High Energy Cosmic Rays
0,1
1
10
18 18,5 19 19,5 20 20,5
uniform distribution,
AGASA data (E 20%)
HiRes 1 Monocular
(E
)
E3 (
10
24 e
V2m
-2s-1
sr-1
)
log10
E (eV)
protons onlyData beyondthe GZK limit:new physics?
CMB
pionE
E’
Origin of neutrinos
• Weak decay of atomic nuclei (Sun/reactors): …n… …p… + e + e (righthanded antineutrino)
…p… …n… + e+ + e (lefthanded neutrino)• Cosmic rays (decay of the pion)
+ (righthanded antineutrino)
+ + + (lefthanded neutrino)• Remnants of the big bang
just as photons (T = 2.7 K background) for all three kinds of neutrinos (e, en ) 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!
Detection via cherenkov light emitted by particles moving “faster” than light
(from antares experiment)
Neutrino detection techniques
Neutrino oscillations in the atmosphere
• Neutrinos in the atmosphere are created in the decay of pions. These are mainly neutrinos
• If the neutrino is a quantummechanical superposition of two neutrinos 1 en 2 it gives rise to oscillations
Place and timeof measurement
Place and timeof production
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
Consequences of mass
• Particles with mass must come as righthanded and lefthanded!
• This is only possible if the neutrino is its own anti-particle (as the photon, but unlike the electron)
Neutrino oscillations in the Sun
• Oscillations arise because the interaction of e with matter differs from the interaction of
(e ‘feels’ electrons, doesn’t!)
• SNO showed that what is missing on e appears as a different kind of neutrino
• Most probably these are oscillations of the type e