My research employs the world's largest scientific apparatus to study the tiniest objects in the universe: the fundamental building blocks of matter. These include the constituents of the atom--the electrons and quarks--that make up everyday objects. But, strangely, nature provides us siblings of the commonplace electron: the muon, tau and three super-light neutrinos; we refer to these six particles collectively as leptons. Similarly, we observe six types of quarks where only two are used to produce your body, a table or a laptop computer. These extra particles are hidden unless we have enough energy to produce them, either in our particle colliders or when cosmic rays interact in our atmosphere. Then, they are produced in abundance but travel only a short distance before decaying quickly back to more ordinary matter. Interestingly, the large energy density needed to produce these particles was also prevalent in the very early universe. Thus, experimental particle physics and cosmology are intimately related.

The Tevatron accelerator, at Fermilab near Chicago, collides intense beams of protons and antiprotons at 2 trillion electron volts of energy. Antiprotons are negatively charged protons, and the two annihilate when they collide. This frees up all this energy and, thanks to Einstein's E=mc2, immediately recondenses back to particles. When this occurs, any particles, including the "siblings" can be produced. We therefore construct our particle detector in the volume around this collision point, and we measure what takes place in each of the million or so collisions every second. This detector, called CDF, discovered the top quark several years ago. Top is the sixth quark and has very unusual properties. It is extremely heavy, with about the mass of a gold atom. This is quite bizarre, as a gold atom's nucleus is made up of about 200 protons and neutrons, each of which is composed of 3 quarks!

The Standard Model of particle physics, which accounts for the various particles and forces we observe, has serious theoretical flaws. These problems relate to how the particles obtain the masses that they evince--masses that we can measure at CDF. Theoretical physicists have therefore postulated extensions to the Standard Model that might explain this properly. These new models predict more fundamental particles exist in nature than observed up until present. In fact, we may have only seen half of them! One particularly appealing theory, Supersymmetry, ties together the matter particles (leptons and quarks) and the force particles (photons, W and Z bosons, gluons). By doing so it provides an elegant explanation for the mechanism that generates the masses of these particles: the Higgs mechanism. At CDF we have spent considerable effort searching for Supersymmetric partners of the leptons, quarks and force carriers. Unfortunately, no such "exotic" particles have been yet observed, but we have used the null results of our searches to set stringent limits on the production and masses of squarks, sleptons and gauginos. Furthermore, by continuing to run our experiments and collecting more data, the chances of discovery will continue to increase.

In 2001, the CDF experiment resumed data taking after a five year upgrade. This new run will continue for the next six years and constitutes an unprecedented opportunity for high energy physics measurements and discovery. During the upgrade, our group has helped build the vertex tracker. Comprised of 750,000 channels of silicon detector positioned right around the collision point, it resolves the hundreds of particle tracks that emanate from every proton-antiproton annihilation. The data from this device are read out with state-of-the-art electronics and combined with those from other parts of the detector so that every event can be reconstructed on dedicated computers and analyzed in real time. Our group is using these data in searches for new physics, such as that predicted by Supersymmetric and the Higgs models. This promises to be an exciting time, since observing these particles would dramatically deepen our understanding of nature at the smallest scale. It would be the discovery of the millennium!

Now, if you'd like to hear about my work on CMS or CACTUS, please ask!


Back to Chertok's homepage
E-mail: chertok@physics (.ucdavis.edu)