Functional links between proteins

(or T) violation arises only from effects of the third family explains why its effects are ordinarily so small. We usually study matter made out of just the first two families, so the only CP-violating effects occur through the small, indirect influence of virtual heavy particles from the third family. Ambitious plans are afoot to study particles containing b quarks directly. When such particles decay all three families are actively in play, and CP-violating effects are expected to be accessible. What does the Standard Model predict for r? This has been the object of some controversy. A major review of the subject quotes r 4 7.7 2 10, but allows for values from 4.2 2 10 to 13.7 2 10. The reason for the spread in this prediction is revealing. Uncertainty arises not so much from any defect in fundamental theory or ignorance of fundamental parameters in the Standard Model, but from weaknesses in our ability to calculate its consequences. For example, there is no simple, reliable way to solve the equations of QCD (quantum chromodynamics) with good accuracy. In making their estimates, theorists resort to rather crude models and drastic approximations, which can come to resemble art more than science. Into the breach have rushed the numbercrunchers, creating a bombshell. By solving the equations of QCD numerically, using ultrafast parallel computers, one obtains, in principle, definitive answers. A group of researchers from Columbia University and Brookhaven National Laboratory now reports that the Standard Model predicts r to be negative — actually, 1120 (5 70) 2 10 — in dire contradiction with the experimental result. Their result reinforces earlier hints of trouble from less definitive numerical work. Moreover, they suggest that the difference between these calculations and previous predictions lies in their treatment of a particular process described by the ‘eye graph’ shown in Fig. 1. Because the source of CP violation in the Standard Model is in principle well understood and in some sense small, experiments in CP violation are especially sensitive to physics outside the Standard Model. Indeed, popular supersymmetry models feature so many potential new sources of CP violation that it is somewhat embarrassing that no deviation from the Standard Model has been observed (until perhaps now). Supersymmetry implies the existence of particles even heavier than the particles in the third family, although there is no evidence for them yet. As always, extraordinary results merit extraordinary scrutiny. If the Columbia/ Brookhaven result holds up, the value of r will join neutrino oscillations as the first indications of physics beyond the Standard Model. Already there are serious proposals for how it might be tied up with supersymmetry. ■