Zoo events
When physicists at Fermilab smash particles together, most of what comes out of the collisions is well understood. But every once in awhile strange things appear in the data—incidents popularly known as zoo events.
Dave Toback, a Texas A&M University professor who works on the CDF experiment, says zoo events are rare by definition, but occur frequently enough to catalogue—like animals in a zoo. "The idea is that you try and collect these animals so you can study them," he says. Toback uses a program called "ZooFinder" that monitors collision data and sends emails to him and other physicists when zoo events occur. "Every so often," he says, "we'll get other physicists together to try and look at the zoo."
Although the exact origin of the "zoo event" term is cloudy, Henry Frisch of the University of Chicago says the concept has evolved into a systematic strategy for finding new physics. "Keeping a sharp eye out for anomalies is a big part of trying to bust the Standard Model of physics," Frisch says, "because we really don't know what we're looking for."
Because anomalies like cosmic rays and improper detector readouts can cause zoo events, some physicists are cautious about using them as a basis for discovery. But Frisch says using the correct approach can be fruitful.
"One has to be very careful not to attribute new physics in cases where it's not, and not to ignore new physics when it is," Frisch says. Toback argues that unexplainable events are especially hard to ignore. "Many great discoveries weren't made with a ‘eureka,'" Toback says. "They were made with a ‘hmmm, that's funny.'"
Dave Mosher
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