Laser spectroscopy of antihydrogen

Precision Tests of Fundamental Interactions
Laser spectroscopy of antihydrogen: In a series of the papers published in Nature, the ALPHA collaboration reported the first-ever laser spectroscopy of antimatter atoms. Over the past several decades, laser spectroscopy of the ordinary hydrogen atom has reached exceedingly high accuracies to the level of 4x10-15 level. Now ALPHA has achieved laser measurements in antihydrogen, with an initial precision of  2x10-10, which was subsequently improved to 2x10-12. The latter is the most precise direct measurement of antimatter properties, and represents a test of matter-antimatter symmetry, known as CPT symmetry, with a parts-per-trillion precision. The results attracted significant attention both from the scientific community and the general public.    

Characterization of the 1S–2S transition in antihydrogen

J.S. Hangst et al., Nature, 557, 71 (2018)

Successful construction of the ALPHA-g antimatter gravity detector

Precision Tests of Fundamental Interactions
Successful construction of the ALPHA-g antimatter gravity detector: In July 2018, the construction at TRIUMF of the time-projection chamber (TPC) for the new antimatter gravity experiment, ALPHA-g, was completed. The TPC detector has been shipped to CERN, where it is currently being tested. The detector is a key component for the ALPHA-g project, whose goal is to measure the gravitational property of antimatter by dropping antihydrogen atoms inside a detector. The TPC will measure the location of the antihydrogen annihilations, from which the effect of gravity will be inferred. According to the equivalence principle in Einstein’s theory of gravity, matter and antimatter should behave identically under the force of gravity. However, no one has ever seen how antimatter falls. The ALPHA-g experiment is set to be the first to do just that.

Canadian laser breakthrough towards laser-cooling of antimatter

Precision Tests of Fundamental Interactions
Canadian laser breakthrough towards laser-cooling of antimatter: In Nature (2018), the ALPHA collaboration reports the first-ever observation of a key atomic transition in antihydrogen, the so-called Lyman-alpha transition. In ordinary hydrogen, this is one of the most important transitions in the Universe, responsible for first light produced after the Big Bang when the electrons and the protons combined to form hydrogen atoms. However, the transition is notoriously difficult to observe in antimatter, partly because of the technical challenges with producing laser light to drive the transition. The observation of the Lyman-alpha transition in antihydrogen was made possible by the development of an innovative laser system by a team from TRIUMF and the University of British Columbia. The Lyman-alpha transition not only provides important information of the structure of the anti-atom, but also can be used to control the motion of antihydrogen. In particular, the laser cooling of antihydrogen will enable the creation of ultra-cold antihydrogen, essential for future spectroscopy and the gravity studies of antimatter.

Observation of the 1S-2P Lyman-α transition in antihydrogen

M.C. Fujiwara, J.S. Hangst, T. Momose et al., Nature, 561, 211 (2018)