The Holy Grail of high-energy physics — the predicted but elusive Higgs boson — is almost within reach, and the Brandeis high-energy physics group, along with other particle physicists around the world collaborating on making the finding, is almost giddy with excitement.
The Brandeis group has contributed since 1994 to collaborative experiments to detect the Higgs particle in the world's largest particle accelerator, the Large Hadron Collider (LHC). CERN, the international agency in Geneva that oversees experiments in the LHC, announced Monday in a progress report the news of mounting experimental evidence for the existence of this critically important speck of nature.
"It's very exciting," says Brandeis physics Professor Craig Blocker, explaining that experiments in the LHC's two detectors have amassed enough evidence of the Higgs particle to suggest much more than an unexplained blip in the data produced by trillions of protons smashing into each other at almost the speed of light.
"The data look very tantalizing but we're not there yet," says Blocker. "We don't have quite enough evidence to claim a discovery but it looks promising — there's a good indication that this particle is there, so we'll probably be able to announce the discovery next year with more data."
What makes the prospect of finding the Higgs particle so electrifying for physicists is that its discovery could put in place the final piece of the puzzle that describes the fundamental building blocks of matter and their interactions — hence its description as the "God Particle." Higgs particles are thought to interact with other subatomic particles to give them mass through a phenomenon known as the Higgs mechanism.
The Higgs mechanism was first described in the 1960s by Scottish physicist Peter Higgs. A few years later, physicist Steven Weinberg applied Higgs' ideas to weak interactions and predicted the Higgs particle. It is the only elementary particle in the Standard Model — the description of the fundamental particles and the forces that hold them together — that has not been observed experimentally yet.
Blocker says detecting the Higgs is challenging because the strength with which it interacts with other particles depends on the mass of those other particles. The Higgs itself is quite massive (for something on the subatomic level); it interacts well with other massive particles, but very poorly with lightweight particles. However, massive particles generally require higher-energy conditions than lightweight particles to record experimentally — energy levels difficult to obtain even inside the mind-boggling fast Large Hadron Collider. Consequently, says Blocker, physicists don't obtain the signature energy decay of a Higgs boson often in the supercollider.
The growing anticipation surrounding the Higgs particle seems almost overshadowed by a gathering anxiety that physicists might actually get what they wish for — a perfectly realized prediction that completes the Standard Model. If that happens says Blocker, "we'd be unhappy — the quest is what's interesting."
Higgs or no Higgs, the chances of particle physicists actually arriving at what Einstein called a "theory of everything" anytime soon seem infinitesimally remote. When it comes to particle physics, says Blocker, it is much more likely that new theories will be generated with each experimental advance.