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| The goal of accelerator-based experiments is to understand how nature works at the smallest distances and largest energies possible. In particular, we ask the questions “What are the smallest building blocks of the universe?” and “What are the forces by which they interact?” Our current answers are codified in the table below which lists 12 fundamental building blocks (the quarks and leptons) and 4 force carriers (the bosons) for the Weak force, the Electromagnetic force and the Strong force. Gravity has a negligible impact here, but is still missing from this theory |  |
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The theory (or mathematical model) which best describes the particles in the table and their interactions is called the standard model. The standard model was initially proposed in the 60’s and early 70’s, and over the past 35 years a series of experiments at SLAC, BNL, Fermilab, KEK and CERN have shown that the standard model describes all experiments well.** However, we have not yet found everything the standard model predicts. In particular, the standard model requires the existence of a new particle, the Higgs Boson, needed to explain how the W and Z boson have non-zero masses. The Higgs boson has not been found yet and searching for evidence of its existance (or conclusive evidence of its non-existence) is a major part of what we do. |
| Einstein’s famous equation E = mc2, shows that high energy (E) corresponds to high mass (m), so with high energy accelerators we can look for particles with large mass. The heaviest fundamental particle observed so far, the top quark, has a mass of 172 GeV, which is slightly less than a single atom of gold. The cartoon to the right shows the conversion of energetic quarks with little mass into massive top quarks and the subsequent decay of the top quarks. |  |
In addition to studying the
known particles looking for discrepancies with standard model
predictions and looking for the Higgs boson, a significant part of our
research involves looking for new particles predicted by theories
(whimsically illustrated to the right) which address possible shortcomings of
the standard model.
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High energy also corresponds to short distances. Regular optical microscopes can measure distances as small as 0.5 mm, or 109 times larger than a proton. With the accelerators we use for research, we study distances as short as 10-10 nm, 10,000 times smaller than the diameter of a proton.
** The standard model has one known shortcoming - it does not incorporate neutrino mixing (and therefore neutrino masses).