Fermilab Ups the Anti(hydrogen)

Thanks to Star Trek, almost everybody has heard of antimatter. So when an experiment at CERN, the European laboratory for particle physics in Geneva, produced the first antiatoms last January--nine atoms of antihydrogen--the announcement made headlines around the world. Now a group of scientists at the Fermi National Accelerator Laboratory (Fermilab) has taken antimatter production one step further.

Glenn Blanford, one of the experimenters, says the team has detected seven antihydrogen atoms in 4 days--and they expect to make 1000 by next September. Even 1000 antiatoms is still too few for physicists who would like to compare spectra of hydrogen and antihydrogen to test nature's basic symmetries. But the experiment is a "good second step" toward usable quantities, according to Harvard University physicist Gerald Gabrielse.

The Fermilab experimenters are using roughly the same antimatter recipe that worked for CERN: They fire a stream of antiprotons, the antimatter counterparts of protons, through an ordinary gas. Once in a while, the interaction spawns an electron paired with a positron--the electron's antimatter version. And even more rarely, the passing antiproton (which has a negative charge) captures the positron (which is positive), forming a complete atom of antihydrogen.

Unfortunately, the antihydrogen atoms are moving at extremely high speeds. "There's no way to study them," says Daniel Kleppner, a Massachusetts Institute of Technology physicist. "You can't do experiments." Blanford admits that the atoms' velocities make matters difficult--and that the scientists need at least a 10-fold increase in antihydrogen production before making even crude measurements of the atoms' spectra. "[The experiment] is very exciting, but it's too early to point at what it's going to do for us," he says.

Posted in Physics