Cold atoms of antihydrogen promise a unique opportunity to study the properties of atomic antimatter, and via comparisons with its well-studied matter-counterpart, the possibility to test fundamental symmetries such as CPT invariance. In order to probe matter-antimatter symmetry at the highest possible precision, it is essential that the anti-atoms be suspended in vacuum to allow for detailed interrogation via laser light or microwaves. The ALPHA experiment, running at the CERN antimatter factory, is now trapping sufficient numbers of antihydrogen atoms to enable these studies.
The best measurements in hydrogen are of the 1S-2S transitions (precision 10-14, determining the Rydberg), the ground state hyperfine interval (precision 10-12), and the 2S-2P Lamb shift. The spectroscopy of the 1S-2P levels is also of interest for laser cooling the anti-atoms to achieve improved precision of the previously mentioned transitions. The trap environment is particularly challenging and requires adaptation of the usual AMO techniques. I will discuss recent measurements of these transitions in antihydrogen, where we have recently reported a 1S-2S measurement with 2 10-12 precision, and discuss prospects for further improvement.
ALPHA collaboration http://alpha-new.web.cern.ch
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