FIGURE 3. The Kobayashi–Maskawa matrix and the unitarity triangle.

The terms of the Kobayashi–Maskawa matrix are complex numbers representing the coupling strengths between the six different quarks of the standard model. Their relation to each other is often represented in the form of a triangle — the unitarity triangle — whose dimensions are proportional to combinations of the matrix terms (V_ub^*, shown here, is the complex conjugate of V_ub). Drawing the triangle defines three angles, and these are the quantities being measured in the current round of experiments at the B factories. Data from many sources, fed into a single plot³¹ (right), already constrain the values of the three angles quite tightly. The B factories will produce more accurate results, to be followed up in even finer detail in the next generation of experiments.