by James Schultz

Banquet guests care little for the backstage details of the food they enjoy. A meal is judged simply, with a from-the-plate-to-the-tongue evaluation of aroma, temperature, texture and taste. But every great meal involves hours of careful planning and execution.

It's much the same with the final phase of physics experiments. Researchers must ensure that their own meticulous preparation leads to a kind of scientific feast that can be enjoyed for years after a given investigation concludes.

But as with any gala, glitches can, and do, occur. At Jefferson Lab, experimental outcomes can be adversely affected by variations in accelerator beam energy, minuscule beam-to-target offsets, changeable densities of the target itself, or problems with the complex array of detectors that track the subatomic debris generated by the collision between target and beam. That's why, says Hall C staff scientist Rolf Ent, teams put their experiments through several trial runs before recording the data they will ultimately analyze.

"You can't afford to have something go wrong hardware-wise," Ent explains. "You can lose a significant percentage of your data. So we measure something old before measuring something new. That way we make sure the beam and targets are functioning properly."

Because all three experimental halls are now routinely taking data, the Lab is handling unprecedented amounts of digitized information. All experimental results are funneled to the Lab's Computer Center and recorded on magnetic tape cassettes that can be accessed upon demand. To date, the Center has handled 40-plus terabytes of information the rough equivalent of 40 million 300-page books. "You want to completely understand every different, little part of your data. You want to make sure the data make sense," Ent points out. Then you go further; you begin interpreting the data in terms of basic physics.

Completely analyzing experimental results is a process that can take up to two years. Ent says the time spent depends on the experiment's degree of difficulty and the experience of the analyzers, a number of whom are usually graduate students or post-doctoral graduates. "Sometimes you're trying to find something very, very small. You're fishing for something very rare. Other times you're looking for something very big. Either way, if you're finished in half a year, it's exceptional."

Toward a New Physics

Some people believe that, as the millennium draws to an end, most major scientific discoveries have been made. What science remains is therefore simply a matter of filling in details. Most physicists, however, dispute this view. JLab chief scientist and Theory Group head Nathan Isgur believes many gaps remain in researchers' understanding of Nature's fundamental workings.

"Why is the nucleus made of protons and neutrons? Where does the force that holds the nucleus together come from?" Isgur asks. "Nuclear physics is still a black box. What we're doing at JLab is opening up the black box and figuring out what's inside and how what's inside works."

A deeper understanding of the physical makeup of the world usually brings practical benefits. Just as in the late 20th century society is still profiting from the development of a theory of electromagnetism from the 19th century, 100 years hence our descendants may be using technologies derived from research into the basic structure of the atomic nucleus.

"Our job is to find the right equations to describe at least that part of Nature we're observing," Isgur says. "When we find them the equations for electromagnetism, for example understanding starts pouring out. That which is unconnected is connected."

There is no guarantee that every experiment will lead to satisfying results. For experimentalists and theorists alike, sitting down together at the physics equivalent of a banquet table to view a given investigation's outcome may raise more questions than it answers. Other, more rigorous studies may be required to address new issues. Yet on certain rare occasions, the details of Nature's grand plan can be suddenly revealed, advancing understanding in one sudden, startling leap.

"An experiment doesn't always end up the way you plan," Ent points out. "Sometimes you find things you weren't expecting. That's the best thing that can happen. It gives you a new insight into physics. That's very exciting."

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