The 1999 Nobel Prize for Physics has been awarded to two Dutch physicists who refined a major part of the mathematical framework of modern particle physics. Today, the Royal Swedish Academy of Sciences announced that Gerardus 't Hooft of the University of Utrecht and Martinus Veltman, an emeritus professor of the University of Michigan, Ann Arbor, will get the prize for turning so-called electroweak theory into a precise tool for calculating particle masses and behaviors.
Following the example of James Clerk Maxwell, who realized in the 1860s that electricity and magnetism are aspects of a single electromagnetic force, physicists yoked together a second pair of forces in the 1960s to create electroweak theory. It united electromagnetism with the weak force, which operates within the atomic nucleus and is responsible for certain kinds of radioactive decay. Electroweak theory predicted new force-carrying particles called W+, W-, and Z0, but it was a frustrating tool at first, tending to yield nonsensical answers about particle masses and behaviors. In 1969, Veltman, then a professor in Utrecht, and 't Hooft, still a doctoral student, started working on a mathematical model that would make sense of electroweak interactions. By 1972 they had published the essentials of their method.
Karel Gaemers, a particle physicist at the University of Amsterdam, says their main contribution to the field is the development of a technique called "renormalization," which makes precise predictions for electroweak interactions possible. This technique allowed, for example, precise predictions of the masses of the W and Z particles, created and detected in 1983 at CERN, the European particle physics laboratory in Geneva. It also pointed to an approximate figure for the mass of the top quark years before it was discovered in 1995 at the Fermi National Laboratory near Chicago. "That was a great success of theory and experiment and calculational method, and 't Hooft and Veltman supplied the calculational method. ... I think the prize was very well deserved," says physicist Steven Weinberg of the University of Texas, Austin, who himself shared a 1979 Nobel prize for developing the original electroweak theory.