Antimatter held for questioning

From Nature:

For physicists, a bit of antimatter is a precious gift indeed. By comparing matter to its counterpart, they can test fundamental symmetries that lie at the heart of the standard model of particle physics, and look for hints of new physics beyond. Yet few gifts are as tricky to wrap. Bring a particle of antimatter into contact with its matter counterpart and the two annihilate in a flash of energy. Now a research collaboration at CERN, Europe's particle-physics lab near Geneva, Switzerland, has managed, 38 times, to confine single antihydrogen atoms in a magnetic trap for more than 170 milliseconds. The group reported the result in Nature online on 17 November. "We're ecstatic. This is five years of hard work," says Jeffrey Hangst, spokesman for the ALPHA collaboration at CERN.

An antihydrogen atom is made from a negatively charged antiproton and a positively charged positron, the antimatter counterpart of the electron. The objective — both for ALPHA and for a competing CERN experiment called ATRAP — is to compare the energy levels in antihydrogen with those of hydrogen, to confirm that antimatter particles experience the same electromagnetic forces as matter particles, a key premise of the standard model. "The goal is to study antihydrogen and you can't do it without trapping it," says Cliff Surko, an antimatter researcher at the University of California, San Diego. "This is really a big deal."

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