Physicists measure ‘the colour and structure’ of antimatter for first time

Physicists from The University of Manchester have a come step close to answering one of sciences biggest questions - why is our Universe made of matter?

Part of the international ALPHA collaboration based at CERN, Dr William Bertsche, and his colleagues from the School of Physics and Astronomy, have helped record the most precise measurement of antimatter ever made. The discovery reveals the spectral structure of the antihydrogen atom in unprecedented colour.

The findings, which are published in Nature, confirm the capabilities of anti-atom spectroscopy and bring the development of ultra-sensitive tests of antimatter one step closer, and with it a potential answer to the question why is our Universe made of matter?

Dr Bertsche explains: “A long-standing challenge for physicists has been to explain why matter, rather than antimatter, survived the Big Bang.

“Current theories suggest that our world should be equal parts matter and antimatter. Luckily for us, this is not the case because life as we know it would not be possible in world with that much antimatter.

A long-standing challenge for physicists has been to explain why matter, rather than antimatter, survived the Big Bang.
Dr William Bertsche, School of Physics & Astronomy

“However, we do not understand why this is the case. Antihydrogen is a unique system to study because theoretically it should have exactly the same properties as Hydrogen. With hydrogen being the simplest atom, consisting only of an electron and proton, it is the best understood and measured atomic system.

“The colour of antihydrogen may help solve this great mystery because this exotic atom is the antimatter equivalent of the hydrogen atom.”

The study looked at approximately 15,000 atoms of antihydrogen, conducting their measurements over a period of ten weeks. A measurement of antihydrogen compared against a comparable measurement on hydrogen can then test the theories of antimatter to extremely high precision. Any slight deviation in the outcome would have vast consequences for our understanding of the Universe.

The team says the results take antihydrogen spectroscopy to the next level. Dr Bertsche added: “This paper reports on the first detailed measurement on the optical colour of any anti-atom. Within the precision of this first measurement, antihydrogen is found to behave as hydrogen would. This shows the way to make improvements on these measurements as well as to probe other properties of antihydrogen to make more stringent tests of theory.”

The team were also able to measure the spectral shape, or spread in colours, of the 1S–2S antihydrogen transition and get a more precise measurement of its frequency.

Professor Jeffrey Hangst, spokesperson for the ALPHA experiment, added: “The precision achieved in the latest study is the ultimate accomplishment for us. We have been trying to achieve this precision for 30 years and have finally done it.”

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