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For the Public - High Energy Physics Tour


One of the ultimate goals of physics is to develop one set of equations that can explain and make predictions for all phenomena found in nature. This was Einstein's great dream, and it has sparked interest in the physics community to pursue such a theory. Currently one hears of theoretical physicists working on a "superstring" theory, and that many feel as though a theory of evverything might be found in the next decade. Well, whether or not superstring theory turns out to be the ultimate theory, we would like to point out that the "super" in superstring comes from another idea called "supersymmetry." We will briefly discuss what this means, and why scientists on CDF are interested in it.

We currently know of hundreds of particles that can exist in nature, all of which form a sort of particle zoo. But scientists normally like simple pictures, and from such a large number of particles came an idea to make the picture of nature neater. This idea led to the quark model, which has eventually devveloped into the standard model of particle physics. The standard model breaks down the universe into twelve basic ingredients that form all the matter we observe (grouped into quarks and leptons), as well as four other types of particles that create the forces and interactions betrween the matter particles (the gauge bosons). One of the main properties that distinguishes quarks and leptons from the gauge bosons is the value of the spin of the particles. Leptons and quarks have spin values that are 1/2 multiples (1/2, 3/2, ...) of a constant and are all called fermions, whereas gauge bosons have integer multiples (0,1, 2,...) of the same constant and are all called bosons.

Supersymmetry is a mathematical idea that states something about the basic ingredients of nature, the leptons, quarks and gauge bosons. It states that each fermion should have a sister particle that is a boson, while each boson should have a sister particle that is a fermion. In other words, the particle zoo should have twice as many occupants than it currently has! Naturally, this is a major theoretical statement, and scientists at CDF want to investigate and see if there is any evidence for the new particles. This has led to new searches for supersymmetric particles (SUSY particles). From the last run CDF was involved in, no evidence for SUSY particles was found. Rather than simply "scrapping" the theory, perhaps the SUSY particles are too heavy to be made by the tevatron, or they are so rare that scientists have not seen them in abundance. Time will tell if supersymmetry is a valid theory, but for more technical reasons many physicists believe it will be found true and will play an inportant role in developing a "theory of everything!"

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