Antimatter at CERN

The first atoms of antihydrogen – the antimatter counterpart of the simplest atom, hydrogen – were created at CERN in 1995. An atom of antihydrogen consists of an antiproton and a positron (an antielectron), which makes it the simplest antiatom. Unfortunately, this does not make it any easier to produce in the lab. It was a difficult task both for the physicists and for the operation team at CERN’s Low Energy Antiproton Ring (LEAR) – where the discovery of antihydrogen took place. The researchers allowed antiprotons circulating inside LEAR to collide with atoms of a heavy element. Any antiprotons passing close enough to heavy atomic nuclei could create an electron-positron pair; in a tiny fraction of cases, the antiproton would bind with the positron to make an atom of antihydrogen.

However, the fleeting existence of the antiatoms meant that they could not be used for further studies. Each one existed for only about 40 billionths of a second, travelling at nearly the speed of light over a path of 10 metres before it annihilated with ordinary matter. In 2011, ALPHA – an international collaboration currently running experiments at CERN's Antiproton Decelerator facility – succeeded in trapping antihydrogen atoms for 1000 seconds. By precise comparisons of hydrogen and antihydrogen, several experimental groups hope to study the properties of antihydrogen and see if it has the same spectral lines as hydrogen. One group, AEGIS, will even attempt to measure g, the gravitational acceleration constant, as experienced by antihydrogen atoms.

The ACE experiment is testing the use of antiprotons for cancer therapy. In 2015, a facility called ELENA will enable all experiments working at the Antiproton Decelerator to get lower energy and more abundant antiproton beams, making it even easier to produce antihydrogen in large quantities.

Voir en français

Featured updates on this topic

21 Jan 2016 – ALPHA shows the most accurate measurement yet of the electric charge of antihydrogen atoms in a new Nature paper

12 Aug 2015 – In a paper published today in Nature, BASE reports the most precise comparison of the charge-to-mass ratio of the proton to the antiproton


24 Sep 2015 – In September 1995 physicists at CERN synthesised the first antihydrogen atoms, paving the way for today’s growing antimatter research

10 Oct 2014 – TEDed and CERN physicist Chloé Malbrunot team up to test the principle of universality of free fall for antimatter

18 Sep 2014 – Latest measurements from the AMS experiment unveil new territories in the flux of cosmic rays

3 Jun 2014 – ALPHA reports a measurement of the electric charge of antihydrogen atoms, finding it to be compatible with zero to eight decimal places

21 Jan 2014 – The ASACUSA experiment at CERN has succeeded for the first time in producing a beam of antihydrogen atoms

8 Aug 2013 – Help the AEGIS experiment at CERN to work out how antimatter is affected by gravity. Just join the dots!

17 Jun 2013 – A ground-breaking ceremony today marked the start of construction of an extension to CERN's antimatter facility

30 Apr 2013 – The ALPHA collaboration has published a paper describing the first direct analysis of how antimatter is affected by gravity

24 Apr 2013 – The LHCb collaboration has made the first observation of matter-antimatter asymmetry in the decays the B0s

25 Mar 2013 – The ATRAP experiment presents most precise measurement yet of the antiproton magnetic moment