The Higgs boson: Closing in on the Sasquatch of particle physics

Tuesday, December 13, 2011 – Globe and Mail

In a centuries-old Swedish castle near the Arctic Circle, in the fading light of a summer midnight, two of the most brilliant particle physicists in the world made a bet over chocolate.

Does the Higgs boson exist?

It’s no idle query: The underpinnings of particle physics, and our assumptions of how all matter interacts, rely on the particle’s not-quite-proven existence. The 47-year search for that proof now costs a billion dollars a year. And esoteric as their goal seems, scientists argue it’s well worth the effort.

On Tuesday, says Robert Garisto, the physicist and editor judging the castle bet, the public finds out “who’s got to save up money to buy chocolate.”

On the pro side was Frank Wilczek, a Nobel Prize-winning theoretical physicist from the Massachusetts Institute of Technology.

Arguing the contrarian’s side was Janet Conrad, a prominent experimental physicist, also from MIT.

At stake were gold-foiled chocolate coins imprinted with Alfred Nobel’s face – an edible facsimile of the prize given to recipients of the award.

So certain was Prof. Wilczek in his conviction, he offered his skeptical colleague 10-to-1 odds.

Assigning Dr. Garisto to adjudicate was the natural choice. He’s a theoretical physicist and editor of Physical Review Letters – the same journal that published, in 1964, the first arguments for what’s now known as the Higgs mechanism.

“They wrote it out, and the rest is history,” Dr. Garisto said in an interview Monday. “It’s a compelling theoretical argument, but you can always say it really, finally has to be tested. … Most theorists would have thought that was a pretty good bet.”

That bet was made in 2005 at an international conference in particle physics in Uppsala, Sweden. The wager, for which Dr. Garisto still has a signed affidavit, was made at a formal banquet in the echoing caverns of Uppsala Castle.

Six years later, the world has news in the quest for the Higgs boson. As of 8 a.m. (ET) Tuesday, scientists at CERN, the European Organization for Nuclear Research, will give a hotly anticipated update on their search.

It’s nothing definitive – nowhere near the stringent standard of proof this type of science demands for an official “discovery,” which would involve (at most) a one-in-a-million chance of error, or misinterpreting a tiny fraction of a second of decaying subatomic particles.

But it gives a long-anticipated glimpse into what the Higgs boson looks like, and whether it’s there at all.

What is HIggs?

The Higgs mechanism is an explanation of why matter has mass.

The theory contends that particles on their own are massless. It’s only when they run into a sticky, invisible field, called the Higgs field, that they gain mass. That Higgs field gives off a tiny particle called the Higgs boson, or so the theory goes. This is all part of the Standard Model of how particles interact.

Until very recently, there had yet to be a Higgs boson sighting. It’s the sasquatch of particle physics, but more important – and, theoretical physicists will tell you, more likely to exist.

The mechanism, the field and the boson are all named after Peter Higgs, a theoretical particle physicist at the University of Edinburgh.

But its origins aren’t that simple: Several people had been doing similar research at the same time; the same journal published articles by Robert Brout, François Englert, Gerald Guralnik, C. Richard Hagen and Thomas Kibble that same year, arguing much the same thing. There’s no shortage of contention over who should really get credit for the theory. But the name stuck.

Since 1964, physicists have been trying to prove that theory and find the particle the Higgs field is supposed to give off.

Rob McPherson has spent the past 15 years chasing Higgs. He moved to CERN after finishing his PhD at Princeton University, and spent years working at the Large Electron Positron, the predecessor of the Large Hadron Collider near Geneva.

Now, the University of Victoria professor is Canada’s principal investigator in the quest for the particle.

In the past two decades, he figures Canada has put about $100-million toward this project. Canadian researchers helped design one of the detectors, a calorimeter that reads these particles’ energy, in this case by smacking photons into super-cold liquid argon and measuring the electromagnetic showers that spray off.

The sci-fi quest captured the public imagination – especially after Leon Lederman’s 1993 book The God Particle: If the universe is the answer, what is the question?

That book brought Higgs into pop-culture discourse. The “God particle” term also irked some particle-physics purists, who argue there’s no good reason to assign deity-like qualities to a subatomic particle that, itself, is really just a byproduct of the field that gives matter mass.

“Here is this beautiful theory … it’s all been done with the scientific method,” Dr. Garisto argued. “To come in at the last minute and describe it using a deity does disservice to the science, but it also does disservice to religion.”

Tuesday’s announcement is actually early: Scientists from the two parallel Higgs-pursuing experiments weren’t expected to present their findings for more than a year.

In part, the change in schedule is the result of better-than-expected data from the Large Hadron Collider.

But as Europe roils in the grips of a financial crisis, it’s also a good time to remind its leaders why a highly abstract research project costing one billion Swiss francs a year, is worth the cash.

“The CERN director clearly wanted to have some conclusion from this year’s data-taking, the way things are going in Europe,” said William Trischuk, University of Toronto professor and director of the Institute of Particle Physics. “His budget is certainly under pressure.”

What’s at stake?

Everything – and nothing.

If Tuesday’s announcement points towards a Higgs boson with a mass between 114 and 141 gigaelectronvolts (about the equivalent of two copper atoms), it would be one of the most significant scientific discoveries in a generation.

But it would prove a theory most physicists have been using for years. And it could take a decade to confirm the Higgs boson’s existence definitively enough to satisfy the scientific community.

The next stage is what Prof. McPherson calls “new physics” – the quest for information beyond the Standard Model.

One quest the Large Hadron Collider and its high-tech successors may take on is the search for “cold, dark matter” – the stuff believed to take up 80 per cent of the universe’s matter, but with no electric charge.

There are no direct practical applications for the science of finding Higgs. But the indirect benefits have been numerous: Variations on the calorimeter Canadians helped design, for example, are used in radiation imaging, Prof. McPherson said.

If the particle didn’t exist, equations outlining how matter works, why it has mass and how it interacts with other matter would unravel. Every textbook on particle physics would need to be ripped up and rewritten.

But to be honest, Prof. McPherson would rather find out there’s no Higgs boson at all, rather than discover a particle that conforms perfectly to Peter Higgs’s theory – with no further revelations.

“It would be a letdown,” he confessed. “We will have really missed a big opportunity for a deeper understanding of how matter came to be.”

If there were no Higgs, “almost all of our computations of what we should see next at the LHC break down. … But that’s okay.”

Graphic by Matthew Bambach/The Globe and Mail


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