Big Bang at heart of physics megaproject

by Daniel McCabe

When you're trying to find out about the origin of the universe, you have to be patient. Take McGill physics professors Tommy Mark and Jean Barrette, for instance.

Since 1990, they've been part of an international team of researchers that's been carefully laying the groundwork for a landmark series of experiments that won't occur until at least 1999.

When contemplating the creation of the cosmos, you also have to think big. Really big. The device being built for the experiment in which Mark and Barrette are involved is roughly the size of a football stadium.

Mark and Barrette are the only Canadian-based researchers contributing to the Pioneering High Energy Nuclear Interaction eXperiment (PHENIX), a massive project involving 400 physicists from 45 institutions in 10 countries.

The PHENIX team is currently constructing the various components of a huge accelerator system called the Relativistic Heavy Ion Collider (RHIC) to be housed at the Brookhaven National Laboratory in Long Island, New York.

The collider will produce temperatures and pressures more extreme than exist in the centres of stars and will hurl heavy ions (dense atoms stripped of their electrons) rocketing toward each other on a collision course near the speed of light.

By smashing the ions against each other under these conditions, physicists hope to duplicate the sort of matter they think existed in the microseconds following the Big Bang--the explosion of the tiny but enormously heavy speck of matter which physicists believe sparked the creation of the universe.

Mark and Barrette are part of the McGill High Energy Physics Group and in Mark's view the PHENIX initiative "is as high energy as any project that has ever been." When the ions crash, it will result in the release of an estimated 200 billion electron volts for each of the protons and neutrons in the colliding ions.

Physicists believe that right after the Big Bang, a primordial form of matter known as quark-gluon plasma briefly flashed into existence. "As the universe cooled and expanded, this 'cosmic soup' became the real matter we deal with today," says Mark.

Quarks and gluons presently exist as constituents within the nuclei of ordinary particles. The PHENIX team's ambitious goal is to set them free and analyze their behaviour under laboratory conditions.

"Did matter really exist in that form at the beginning? That's basically what we're trying to find out. We view quarks as the building blocks of all matter."

Mark says the PHENIX team hopes to answer specific questions relating to the nature of matter. "For instance, why do quarks confine themselves inside neutrons and electrons? What keeps them there? The mechanism that we believe is responsible is still just theoretical conjecture."

Barrette says McGill's PHENIX researchers are far too busy to get anxious about the long wait until 1999.

"We've been building part of the detection system for PHENIX and there are all kinds of deadlines associated with that. We're busy preparing for the experiment and we're already doing related research at Brookhaven. If anything, we're pressed by time."

Mark and Barrette are primarily responsible for the construction of part of the PHENIX tracking detector system which will monitor the aftermath of the heavy ions collision. McGill and Columbia are the only universities entrusted with supervising the building of PHENIX subsystems--the rest of the work is being done by U.S. national laboratories.

Armed with $3.2 million in PHENIX funding, Mark and Barrette went shopping for components for their portion of the detection system. They settled on a research-intensive, high-tech firm in the Maritimes which will use the sorts of durable fibreglass and carbon fibre materials commonly used in aerospace designs.

"It was nice to be in a position where we had that kind of money to spend," says Mark, but the process hasn't all been to his liking. "We're budgeted down to each nut and bolt and the accounting process is exceedingly stringent. It's very time consuming. There are days where I feel like I'm more of an accountant than a physicist and I don't particularly enjoy that."

More troublesome has been the lack of support from the Canadian government. As McGill played an increasingly important role in the PHENIX project, Mark was hopeful that Ottawa would sign on with the other countries contributing to the financing of PHENIX, including the U.S., Japan, Russia and Sweden.

It didn't happen, and Mark says he almost left the project as a result. "I nearly quit. I thought, 'How can our partners take us seriously when our own government won't support us?' Because we couldn't get any Canadian money, I was afraid we would be relegated to obscurity. But the Americans convinced me to stay. The U.S. Department of Energy has been tremendously supportive."

Barrette says that the graduate students he and Mark supervise are active participants in the PHENIX work.

"All of our post-docs and graduate students are involved in this. Three of our graduate students are directly involved in PHENIX, while two others are active in related research involving the Brookhaven facilities. Some of our students are busy doing simulations of the (planned PHENIX experiments)."

As the project progresses, Barrette expects the profile of the student members of the team will evolve.

"We've been busy building the detection system so the students working with us tend to be interested in the hardware associated with this kind of work. The next generation of students in our labs will be people who will look at the first data that comes in from PHENIX and they'll be trying to make physics out of that data."

Scientists in other fields sometimes look with envy at the way in which the international physics community has banded together to pursue large-scale research.

The observation draws a chuckle from Mark. "We don't really have a choice. The scale of what we're trying to accomplish gets bigger and bigger every year. In the 1960s, if you had 10 or 20 physicists working together on a project, that was considered large scale. If you look at everybody who'll be involved in using the RHIC--not just the PHENIX people--there are almost 1,000 people associated with this initiative.

"It's just like running a corporation, only harder, because each and every physicist tends to be an extremely independent thinker. How do we make it work? We do it because we have to. No single country can afford to do it all anymore--those days are over."

As the leader of the only Canadian team active in PHENIX, Mark says he feels a special responsibility. "I don't want anybody to ever say that Canada is falling down on this job. We realize we're representing the whole country in this project and that keeps us on our toes."