1. SPH4U
Elementary Particles

2. The 4 forces of Nature Weak Electromagnetic weak charge Electric
Beta-decay
pp fusion
Electromagnetic
TV, PCs
Magnets
e- e+ creation
weak
charge
Electric
charge
Strong
Quark binding
Gravity
Responsible of
Keeping us
well-planted on earth
strong
charge
mass

3. From the atom to the quark
How small are the smallest constituents of matter?
<10-18 m
< m
~ m
~ m
~ m
Atoms and sub-atomic particles are much smaller than visible light wave-length
Therefore, we cannot really “see” them (all graphics are artist’s impressions)
To learn about the sub-atomic structure we need particle accelerators

4. Protons and neutrons in the quark model
Quarks have fractional electric charge!
u electric charge + 2/3
d electric charge -1/3
proton (charge +1)
neutron (charge 0) u u u d
So we know now that protons and neutrons are made of quarks. d d

5. Force Particles (summary)
Particles interact and/or decay thanks to forces
Forces are also responsible of binding particles together
Strong: gluons
Only quarks
(because of their
colour charge)
Weak: W+, W-, Z0
Leptons and quarks (only force for neutrinos)
Electromagnetic:g
Quarks and charged leptons (no neutrinos)
Gravity: graviton?
Still to be discovered
Negligible effects on particles

6. The Standard Model Framework which includes: Not gravity! No quantum
Matter
6 quarks
6 leptons
Grouped in three generations
Forces
Electroweak:
g (photon)
Z0, W±
Strong
g (gluon)
Not gravity! No quantum
field theory of gravity yet..
H= the missing ingredient: the Higgs Boson
Very successful to describe all observed phenomena in the
subatomic world so far. But there ought to be more..