The discovery of the Higgs boson, often referred to as “the God particle” – a name many particle physicists say they detest but for its ability to let people know what they’re talking about – brings these scientists closer to understanding mass and its origins. Bowdoin Professor of Physics Stephen Naculich helps bring the rest of us up to speed on what it all means.
Everyone today knows that the world is composed of tiny subatomic particles held together by several types of forces. One hundred years ago, when Rutherford discovered the proton, this was still a revolutionary idea. Over the course of the next 50 years, new subatomic particles were discovered, such as the photon, neutrino, muon and hundreds of others, to the increasing bewilderment of physicists.
Then, around 1975, in a joint effort, physicists unraveled this vast puzzle by constructing the “standard model of particle physics,” which purported to explain the plethora of data in terms of a handful of particles called quarks, leptons, and vector bosons, some of which had not yet been seen. Over the course of the next 20 years, all of these newly-predicted particles were detected in particle accelerators in Europe and the United States, with one exception.
That exception, known as the Higgs boson (named after one of its proposers, the British physicist Peter Higgs), was necessary to make the picture complete. Without this particle (or something akin to it), all the other particles of the standard model would be massless, like the photon. They are not. The conclusion is that either the Higgs boson must exist, or the whole standard model falls apart.
For physicists, the discovery of the Higgs boson represents not the end but the beginning of the search.
The problem was that no one had yet detected a Higgs boson, for the simple reason that it is incredibly massive itself, and therefore exceedingly unstable. To discover this particle it was necessary to build a particle accelerator much larger (and hence capable of producing much more massive particles) than any then existing.
Construction of two underground particle accelerators was begun in the early 1990s: the Superconducting Supercollider (SSC) in Texas (in a tunnel 54 miles in circumference), and the Large Hadron Collider (LHC) on the Swiss/French border (in a 17-mile tunnel). Although the SSC would have been far more powerful, a budget-conscious U.S. Congress canceled it in 1993, thus losing Americans the chance to discover the Higgs boson.
Construction of the LHC proceeded more slowly, but it was finally completed in 2010. On Wednesday, after two years of taking data, physicists at the LHC have announced that they have obtained conclusive evidence for the existence of the Higgs boson, which is 133 times as massive as the proton. This is a satisfying vindication that the standard model provides an extremely accurate description of the subatomic world.
Accurate but not complete. Physicists already know that the standard model of particle physics, while esthetically satisfying, does not provide a comprehensive description of nature. For example, it cannot account for massive neutrinos or dark matter, two relatively recent discoveries.
For physicists, the discovery of the Higgs boson represents not the end but the beginning of the search. The LHC will continue to take data over the next decade, and we are all hoping for the discovery of new, unexpected particles that will provide valuable clues for the construction of an even more comprehensive and accurate theoretical description of the world around us. The search goes on.