Why is Antimatter Behaving Badly?

Does antimatter behave differently than ordinary matter? Recently, an experiment conducted on hybrid matter-antimatter atoms has defied researchers’ expectations.So far physicists have found nothing amiss, no sign that antimatter particles—which are just the oppositely charged counterparts of familiar particles—obey different rules. In 2013, Dr. Anna Sótér was working at the CERN laboratory on a new antimatter experiment. Her group assembled hybrid matter-antimatter atoms by firing antiprotons into liquid helium. How cool is that...literally! Antiprotons are the negatively charged counterparts of protons, so an antiproton could occasionally take an electron’s place orbiting a helium nucleus. The result was a small band of “antiprotonic helium” atoms that could be used to test deviations in the behavior of matter vs. antimatter via differences in their spectra. Whereas the spectral lines of normal atoms would have behaved completely unpredictably in the dense fluid, broadening by one million times, the antimatter hybrid atoms did the opposite. Below about 2.2 kelvins, where helium becomes a “superfluid,” they saw a line almost as distinct as the best they'd seen in ordinary helium gas. Despite presumably being battered by the surroundings, the Frankenstein matter-antimatter atoms were behaving in unison.