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Why BTeV?

The Standard Model has been the backdrop of particle physics theory for more than a quarter of a century. It is a combination of three of the four known fundamental forces - electromagnetism, strong nuclear force, and weak nuclear force (gravity is the fourth). It also contains the fundamental particles which make up the universe which are the six quarks (up, down, charm, strange, top, beauty) and six leptons (electron, muon, tau, electron neutrino, muon neutrino, tau neutrino). All of these particles are partnered with antiparticles with opposite charge but the same mass. This Model is very unsatisfying, however, because it asks more questions than it answers. The Model does not tell us why there are three generations of quark doublets and three generation of lepton doublets. The Model also fails to predict the masses of these particles. It is believed by many that a more fundamental theory will be able to predict many of the parameters of the Standard Model which today must be measured by experiments. Physicists hope this more fundamental theory will also include the gravitational force which is not in the Standard Model.

BTeV is an experiment which is designed to deeply probe several aspects of the Standard Model. At the very least, BTeV will make very precise measurements of many Standard Model parameters. It is hoped that these precise measurements will reveal weaknesses in the Standard Model which will point the way to a more fundamental theory.

One of BTeV's main goals is to precisely measure CP violation in the beauty quark system. CP violation was first observed in strange quarks in 1963 and recently in beauty quarks at BaBar and Belle. CP violation causes particles and antiparticles to behave differently. There are two main reasons to study CP violation. The first reason is that many theories which provide extensions or replacements for the Standard Model predict effects in this realm. The second reason is that one of the big mysteries of the universe is why the universe is composed of matter instead of antimatter. The prevalance of matter over antimatter appears to require a large CP violating process sometime during the early formation of the universe. Although the levels of CP violation in the Standard Model are not large enough to explain this effect, it is the only place where CP violation has been observed and is therefore a natural place to look for more answers.

The BTeV experiment has been approved by Fermilab and is currently being developed. Construction should start in 2005 and should begin collecting data in 2009.

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