The Accidental ParticleThey're turning on the Large Hadron Collider. Don't expect the Higgs boson to show up.

(Continued from page 1)

PRINTDISCUSSE-MAILRSSRECOMMEND...SINGLE PAGE

FacebookMySpace Mixx Digg Reddit del.icio.us Furl Ma.gnolia SphereStumbleUponCLOSE

Meanwhile, a young Scottish physicist named Peter Higgs was interested in an entirely different area of particle physics: the strong force. Here, too, no one knew how to create a consistent theory without also predicting pesky, nonexistent Goldstone bosons. At least until 1964, when Higgs proposed a solution.

Higgs' idea, now called the Higgs mechanism, was to expand the playing field: He studied what happens mathematically if you suppose that force carriers all act the same within the scope of the theory you're trying to build but behave differently when they meet something outside the theory. (This outside influence could be one or several new particles, or it could be something you already knew about but which you wouldn't expect to be relevant to your theory.) He found that it's possible for some force-carrying particles to interact so strongly with an outside particle that they become inextricably entwined, such that what experimenters saw in the lab were really mixtures of the two. Other force-carrying particles don't interact with the outside particle at all. If Higgs was right, all of the force-carrying particles would be very light, but some would appear heavy because they mix with this massive particle. And that means there wouldn't be any Goldstone bosons to worry about.

The original work on the Higgs mechanism didn't worry about the details of the outside particle; to make his point, he just made the simplest possible choice mathematically. The important thing was that, whatever was at the heart of the Higgs mechanism, it could be massive enough to explain why no one had seen it at work.

It wasn't until 1967 that Steven Weinberg and Abdus Salam tried using the Higgs mechanism to save Glashow's electroweak theory. But to get the Higgs mechanism to work, they needed to pick a specific particle from outside the theory—a consideration that Higgs didn't have to worry about when he developed his mechanism abstractly. We now know that there were several things that Weinberg and Salam could have proposed that would have fit snugly into their big theory. One set of possibilities, now known as Technicolor models, would have posited a whole bunch of new fermions, rather than a new boson. (Weinberg worked out the specifics of Technicolor models in 1980.) A related set of theories might have accounted for the mass of the force-carrying particles with an exotic interaction—called a condensate—between the top quark (which has since been observed) and its anti-particle.

The ideas behind these alternatives were already well-established in 1967, but there was no evidence to lead Weinberg and Salam toward any one of them. So they chose the most parsimonious possibility as a placeholder until experiments could catch up with a more complete picture of the electroweak force: They published their theory with the single new elementary particle that Higgs originally used as an example and that we now call the Higgs boson. Nothing in the rest of the theory compelled this decision, and though we now have considerable evidence for the Higgs mechanism, we don't have any for the eponymous boson.

Why, then, does the Higgs boson get so much attention, among physicists and in the popular press? Weinberg and Salam's papers, though ignored until the early 1970s, are now immensely influential because of the theory's other predictions. Indeed, Glashow, Weinberg, and Salam shared the 1979 Nobel Prize for their electroweak theory. In 1974, John Iliopoulos cobbled together the Glashow-Weinberg-Salam electroweak theory—Higgs boson and all—with a theory of the strong force to write down the Standard Model as we now understand it. Over the last 35 years, as the Standard Model recorded success after success, it became easy to forget that the Higgs boson is—and has always been—independent of the rest of the theory.

PRINTE-MAILRECOMMEND...RSS

FacebookMySpace Mixx Digg Reddit del.icio.us Furl Ma.gnolia SphereStumbleUponCLOSE

SPONSORED CONTENT

• Swine Flu
  Here's what you need to know.
  Nov. 3, 2009
• Emote Control
  Why couldn't we tell that the balloon boy's parents were faking their distress?
  Chris Wilson | Oct. 30, 2009
• The Fat Premium
  Congress toys with a silly plan to make Americans lose weight.
  Daniel Engber | Oct. 29, 2009
• Search for more Science articles
• Subscribe to the Science RSS feed
• View our complete Science archive