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A molecule is a collection of atoms held together by electromagnetic
forces. Atoms are made up of electrons and nuclei, also bound
together by electromagnetic forces. Nuclei are made up of protons
and neutrons, which in turn are made up of particles called quarks,
bound inside protons and neutrons by the strong nuclear force.
By contrast, the electron has no known internal structure and,
having nothing to do with nuclear forces, is called a lepton.
Quarks and leptons are currently believed to be the elementary
(i.e. non-composite) constituents of matter. These fundamental
particles interact via the four known forces of the universe--the
strong nuclear force, the weak nuclear force, electromagnetism,
and gravity--by the exchange of force particles. These are called
"virtual" particles because, as a consequence of the Heisenberg
Uncertainty Principle, they only exist for a fleeting moment of
time. (For example, nuclei and electrons are electromagnetically
bound into an atom by the exchange of virtual photons.) Understanding
quarks and leptons and how they interact is the goal of nuclear
and particle physics.
Dr. Schramm's research deals with
several different theoretical aspects of the Standard Model of particle
physics. Most recently, he has worked on calculational techniques for predicting
what particles may be produced when protons or nuclei collide at high energy.
Particles can be created from the kinetic energy of accelerated particles
by means of the famous expression E=mc2; studying these interactions helps
to understand the forces involved.
For example, the effects of the short-ranged
nuclear forces can be separated from the long-ranged electromagnetic if
the speeding nuclei do not hit head-on, but rather pass by one another
in a "peripheral" collision. The electrically charged nuclei exchange photons,
which can fuse to create quarks and leptons. |
