Monday, May 11, 2020

Antihydrogen Is Stable

A simple hydrogen atom (i.e. a proton with a single electron) is stable and does not decay naturally. Anti-hydrogen (i.e. an antiproton with a single positron) should do the same so long as it doesn't encounter ordinary matter. But, making anti-hydrogen and storing it in a way so that it doesn't encounter ordinary matters isn't easy.

The older record lifetime of anti-hydrogen was 16 minutes and 40 seconds, about the same as a free neutron, which is about the same the longest lived hadron (i.e. fundamental particle made of quarks bound by gluons) that isn't stable (a proton doesn't decay). There are atomic isotopes that decay more slowly, but that wouldn't be expected for anti-hydrogen.

Now, the mean lifetime of an anti-hydrogen, from a sample size of 1,000 anti-hydrogen atoms, has been confirmed by the ALPHA Collaboration to be (as widely expected) at least 66 hours, two orders of magnitude more than the previous measurement and longer than any individual hadron. Thus, this relatively inexpensive experiment confirms in a manner independent of particle colliders, that the Standard Model is correct.

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