TESLA Brochure - ACFA Joint Linear Collider Physics and Detector ...

34
Holding the world together:The forces
(also known as interactions) are transferred
by means of exchange particles,which are
specific for each type of force:the photon—
otherwise known as the quantum of light—
mediates the electromagnetic force;the
gluons mediate the strong force,which affects
the quarks;the neutral Z particle and
the positive and negative W particles mediate
the weak force.The gravitational force is
mediated by the massless,and as yet undetected,
graviton.
Gluon
Carrier of the:
Affects:
Strong force
Quarks
Responsible for:
Holding together the
atomic nucleus
A Key to the Universe?
(Super)Symmetry
There is much to suggest that the key to understanding the way elementary
particles and the forces of nature behave is to be found in the very
early phase of the universe. Compared to its current state, the universe
seems to have been simpler, more clearly organized and more “democratic”
back then.Physicists would say it was more “symmetrical.”Fewer seemingly arbitrary
assumptions and parameters are required to describe this early phase
of the universe. Instead, there was a greater consistency and uniformity, from
which the whole multiplicity of nature subsequently developed over the
course of time. It was Albert Einstein’s great ambition to help trace all the
fundamental laws of nature back to an original, supreme symmetry—an underlying
principle that explained everything. In fact,even before Einstein’s day,
important steps toward such a unified theory had already been taken—advances
that would later prove to be of immense practical use.Today, Einstein’s
legacy lives on in the field of elementary particle research.The Standard Model
comprises all that is currently known about the properties and behavior of
particles and the forces of nature.
The Standard Model describes two different fundamental forces: the strong
and the electroweak interactions between elementary particles. The strong
force holds the atomic nucleus together and is therefore responsible for stabilizing
matter. The electroweak interaction causes the sun to shine, lights to
burn, and dominates behavior in the worlds of chemistry and biology. However,
the force of gravity, which keeps our feet on the ground and the stars in
their orbits,cannot be explained in terms of the Standard Model.
Photon
Particle of light
Electromagnetic force
Quarks and charged
leptons
Chemistry, electricity and
magnetism
W and Z bosons
Weak force
Quarks and leptons
Radioactivity,
solar energy
Graviton
Gravitational force
All particles
Holding together
the earth, the Sun,
the solar system …