Structures in MicroUniverse

1
Structures in Micro-Universe

• The atomic level
• The nuclear level
• Elementary particles and the quarks
• The four universal forces
• The Standard Model
• The Superstrings Model

2
The Atomic Level

• 19th century molecules seen through X ray
  experiments their composition of atoms is
  assumed
• 1897 J.J.Thompson extracts electrons from atoms
• 1911 E.Rutherford demonstrates that atoms contain
  a massive nucleus
• 1913 N.Bohr shows that electrons must have
  quantum states in atoms
• 1926 E.Schrodinger and W.Heisenberg formulate
  quantum mechanics, which describes atomic
  structures

3
Quantum World

• The idea of quantum states
• Atomic spectra
• 4 quantum numbers characterize an atomic state
• The Uncertainty Principle (Heisenberg)
• The relativistic Uncertainty Principle
• Subatomic particles behave like probability waves
• Atomic phenomena occur with certain probability,
  which can be measured experimentally

4
Electromagnetic Interactions

• Matter at the molecular and atomic level is
  governed by the electromagnetic force.
• How do two electrical charges interact ? The
  answer requires quantum mechanics, relativity and
  anti-particles.
• The fact that an electron has an electric charge
  means that it pulses photons (explained by the
  relativistic uncertainty principle). These
  photons are virtual (they cannot be
  measured).

5
Explaining the Electrical Force
How does the virtual photon interact with the
electron? An experiment in 1932 showed that a
photon can break into an electron and a
positron (anti-electron). Also, experiments
showed that an electron will annihilate a
positron producing photons. The mysterious
interaction from a distance of the two
electrons becomes contact-type interaction
between electrons and positrons described by the
Feynman diagram shown here.
e-
e-
e- e
virtual photon
e-
e-
Feynman diagram
6
Deeper Structures inside Atoms

• 1932 M.Curie discovers artificial nuclear
  transmutations, J.Chadwick discovers the neutron
  and R.Anderson discovers the positron.
• Nucleons are needed in the structure of atomic
  nuclei
• Although 100,000 times smaller than atoms, nuclei
  are also described by quantum mechanics
• 1934 H.Yukawa showed that nuclear interactions
  exchange pions, particles found experimentally in
  1945

7
Nuclear Force

• Using accelerated particles to hit nuclei one
  moves nucleons (protons or neutrons) to more
  energetic states and in certain cases to the
  nuclear fusion and fission (nuclear energy).
• Hydrogen fusion is the source of energy in the
  Sun, while uranium fission is the source of
  energy in nuclear reactors
• Explanation Binding particles is equivalent to
  freeing energy, as their separation needs energy.
  Producing a tighter-bound nucleus liberates
  nuclear energy.

8
Nuclear Binding Energy
Iron
uranium
Binding energy per nucleon (in MeV)
hydrogen
100
200
number of nucleons
9
The Weak Nuclear Force

• The weak nuclear force is in action each time
  that one particle disintegrates into another.
• Without it nature could not manufacture nuclei
  heavier than hydrogen through nuclear fusion.
• The weak nuclear force acts at very short
  distances exchanging weakons.
• The weak force is universal the same force that
  disintegrates nucleons will disintegrate mesons
  or muons.

10
The Universality of Forces
p
p
e-
e-
virtual photon
virtual photon
The electromagnetic force
no
muonic neutrino
p
muon
virtual weakon (w-)
virtual weakon
positron
(w)
e-
anti-electronic neutrino
electronic neutrino
The weak nuclear force
11
The Particles Jungle - Classification by Weight
Experiments with cosmic rays or with particles
from accelerators produced a large number of new
heavy particles, most of them with very short
lives. A first attempt to categorize particles
was based on their weight.
Baryons proton, neutron, etc
Hadrons
weight
Mesons pion,etc
electron, electronic neutrino muon, muonic
neutrino
Leptons
Note for all particles there are anti-particles
discovered.
12
The Particles Jungle - Classification by Spin

• One way to think of spin is to imagine the
  particles like little tops spinning about an
  axis.
• Better interpret spin as a measure on how the
  particles look from different directions.
• It appears that the Universe contains two types
  of particles fermions with spin ½ and bosons
  with integer spin (0,1,2).
• Fermions make up the matter in the Universe,
  while bosons are associated with the mechanism of
  forces.

Fermions baryons, leptons
Bosons photon, weakon, mesons
13
Order Among Particles

• After 1950 hundreds of new particles (baryons,
  mesons, leptons) were discovered. Their lives
  were short by comparison to events in macro but
  very long by comparison to the collision time.
• Experiments suggest conflicting pictures on which
  particles are more basic.
• 1964 MurrayGell-Mann at Caltech proposes that all
  hadrons are made of quarks. However leptons did
  not have subparticles.

14
The Quarks Model
Qem
u (333MeV)
2/3
d (338MeV)
s (540MeV)

-1/3
Quarks
The use of Gell-Manns quark model in the
organization of barions. Qem is the
electromagnetic charge, while Qsl is the
strangeness charge.
15
Searching for Quarks

• Huge energy was needed to obtain a pilot wave of
  a wavelength smaller than the size of a proton
  (10-15 cm). An electron for instance must be
  accelerated to an energy of 20 GeV.
• Results at SLAC, Fermi-SPS and at CERN-ISR showed
  that the incident particles collided with
  particles inside the proton.

16
The Colour Force

• No free quarks were observed.
• Quantum chromodynamics
• Colour force,
• Gluons.
• The colour force is also called the strong
  nuclear force, as the nuclear binding can be
  shown to be just a derivative of the colour force.

17
A New Quark Needed
Building Bricks of the Matter
Qel
Qel
?
electron
muon
u (333MeV)
-1
2/3
muonic neutrino
neutrino
d (338MeV)
s (540MeV)
0
-1/3
Leptons
Quarks
1974 Sheldon Glashow proposes a new quark c (with
charm). 1976 first experimental proof of its
existence -the J/psi particle. Samuel Ting at
Brookhaven and Burton Richter at Stanford find
almost simultaneously a particle with a 3.1 GeV
mass.
18
Particles with Charm

• 1976 anti-proton with charm (udc) at Fermi.
• With charm the symmetry of the two groups of
  baryons look like in the diagrams shown on the
  right.

19
Super Heavy Particles

• 1975 an experiment at Stanfords SPEAR discovered
  a super-heavy electron baptized tau and a new
  neutrino associated with the tau lepton.
• A theoretical model with 6 leptons and 6 quarks
  was already proposed by H.Harari. He named the
  two extra quarks top and bottom, but those names
  were soon changed to the more poetic names truth
  and beauty.
• 1977 at Fermi lab L.Lederman and his team
  observed the first particle with beauty a meson
  with b and anti-b having a total mass of 9.7 GeV
  (about 10 times the mass of a proton). It was
  named Upsilon.
• August 2000 the first particle with the truth
  quark.
• The modeling of the Big Bang provides support for
  a model with 6 leptons and 6 quarks.

20
The Standard Model
Building Bricks of the Matter
Qel
muon (105MeV)
tau (1800MeV)
electron (0.5MeV)
Leptons
-1
tau neutrino
muonic neutrino
neutrino
0
Qel
t (12000MeV)
c (1550MeV)
u (333MeV)
2/3
Quarks
b (4700MeV)
d (338MeV)
s (540MeV)
-1/3
21
The Standard Clasification
Leptons Anti-leptons
Quarks
Anti-quarks
Mesons Anti-mesons
Baryons
Anti-baryons
Bricks
Hadrons and Anti-hadrons
Force
Acts on
Force Carriers
foton electromagnetic
all charged particles weakon
weak all particles gluon
colour
quarks graviton gravitational all
particles
22
The Second Unification The Electro-Weak Force

• No similarities between electromagnetism
  (electrical wires, the compass) and the weak
  nuclear force (the disintegration of nuclei or of
  heavy leptons).
• No similarities between their carriers the
  photon is neutral and with zero mass, the weakon
  is usually electrically charged and has a large
  mass (about 50GeV)
• But in spite of all these differences the two
  forces were proven to be closely related.

23
The carrier of the weak nuclear force
Each weakon changes its composition depending on
circumstances. This magic behaviour (justifies
the name universal alchemist) allows the weak
force to act on all the particles. The Zo diagram
shows that this weakon can have the same
composition as the photon, the carrier of the
electromagnetic force.
W
e
ud
ud
e
e
ud
W-
du
du
e
du
e
Zo
dd
ss
ee
cc
uu
24
The Electro-Weak Force

• 1968 S.Weinberg and A.Salam unified the gauge
  field theories corresponding to electromagnetism
  and weak force.
• 1960 J.Goldstone and P.Higgs show that when
  nature breaks symmetry it creates some heavy
  bosons - the Higgs bosons.
• Weakons are heavy because they couple with Higgs
  bosons.

25
Experimental Support

• 1973 At CERN experiments with Zo and W bosons in
  action.
• 1984 CERN uses the first proton-antiproton
  supercollider to produce weakons and their masses
  were agreement with the theory.
• 2000 Higgs bosons were discovered experimentally.

26
Limitations of the The Standard Model

• The problems with the Standard Model can be
  classified as
• Not a true unification of all 4 forces
• Too many parameters (27)
• The mystery of the 3 generations
• The model of a generation
• - No explanation for the fact that the
  charge of an electron is rigorously equal to that
  of a proton.
• - No explanation for the fact that colored
  fermions have fractions of electric charges,
  while white fermions have integer charges.

27
Theoretical Alternatives

• The most successful are
• Grand Unification Theories (GUTs)
• Compounds Models such as the Pati-Salam preons.
• Super-symmetry (SUSY) Models
• Superstring Theories
• How to choose ?
• Theoretical Consistency.
• Experimental verification (predictions)

28
The Pati-Salam Model
Preons
d
u
s
c
red
blue
green
violet
Muonic Neutrino or
Neutrino or
ured
cred
Same for blue and green
uviolet
cviolet
dred
sred
Muon or
Electron or
dviolet
sviolet
29
The Life of a Proton

• Pati-Salams model showed that protons lifetime
  is 1031 years (in their model the lifetime of a
  quark is 10-9 but the chance of this happening in
  the same time for all 3 quarks is extremely
  small).
• Experimental work looks for a proton
  desintegration in a large sample of more than
  1031 protons.
• 1977 in a South African gold mine an experiment
  established a lifetime of 1029 years.
• 1983 in the Mont Blanc tunnel a 150 tons detector
  obtained data corresponding to 1031 years.
• Experiments at the bottom of the Pacific failed
  to obtain and positive results.

30
GUTs

• Put together tables of quarks and leptons
  together with the carriers of forces in their
  interaction
• Use Group Theory to incorporate all known
  particles
• Allow quarks to desintegrate into lepton through
  the hyperweak force (X bosons)

31
Changes of Symmetry

• Going deeper inside matter the number of
  forces decreases. This diagram shows what happens
  with 3 of the 4 universal forces
• hyperweak color, electroweak
  3 forces
• 10-29 cm
  10-16 cm
• Higgs bosons are created through the change
  of symmetry and they are responsible for the mass
  of the weakons and X bosons.

32
SUSY Models

• Puts together fermions and bosons
• The most succesful is Super-Gravitation Model
  (SUGRA)
• Uses the space-time symmetry
• Includes gravity
• Uses 11-dimensional spaces

33
Visualizing Extra-Dimensions

• Michio Kakus Hyperspace
• Visualizing a Sphere in Flatland.

34
Superstrings

• The basic idea is that particles correspond to
  resonances in the vibration of some small
  strings.
• These strings extremely small 1020 times smaller
  than a proton (or 10-36 cm).
• Superstrings and multidimensional branes move
  in a space with 11 dimensions.
• This theory is the best candidate for the Theory
  of Everything