Topic

Antimatter

In 1928, British physicist Paul Dirac wrote down an equation that combined quantum theory and special relativity to describe the behaviour of an electron moving at a relativistic speed. The equation – which won Dirac the Nobel prize in 1933 – posed a problem: just as the equation x2=4 can have two possible solutions (x=2 or x=-2), so Dirac's equation could have two solutions, one for an electron with positive energy, and one for an electron with negative energy. But classical physics (and common sense) dictated that the energy of a particle must always be a positive number.

Dirac interpreted the equation to mean that for every particle there exists a corresponding antiparticle, exactly matching the particle but with opposite charge. For the electron there should be an "antielectron", for example, identical in every way but with a positive electric charge. The insight opened the possibility of entire galaxies and universes made of antimatter.

But when matter and antimatter come into contact, they annihilate – disappearing in a flash of energy. The big bang should have created equal amounts of matter and antimatter. So why is there far more matter than antimatter in the universe?

Check out this timeline for an overview of antimatter research

 

At CERN, physicists make antimatter to study in experiments. The starting point is the Antiproton Decelerator, which slows down antiprotons so that physicists can investigate their properties.

 

The Antiproton Decelerator at CERN slows down antiprotons so they can be used to study antimatter

The Antiproton Decelerator

Not all accelerators increase a particle's speed. The AD slows down antiprotons so they can be used to study antimatter

More about the Antiproton Decelerator


Antimatter experiments at CERN

In the antimatter hall at CERN, numerous experiments are using antiprotons from the Antiproton Decelerator to investigate the properties of antimatter.

 

ACE brings together an international team of physicists, biologists and medics to study the biological effects of antiprotons

ACE

ACE brings together an international team of physicists, biologists and medics to study the biological effects of antiprotons

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AEGIS uses a beam of antiprotons from the Antiproton Decelerator to measure the value of Earth's gravitational acceleration

AEGIS

AEGIS uses a beam of antiprotons from the Antiproton Decelerator to measure the value of Earth's gravitational acceleration

More about AEGIS

ATRAP compares hydrogen atoms with their antimatter equivalents - antihydrogen atoms

ATRAP

ATRAP compares hydrogen atoms with their antimatter equivalents – antihydrogen atoms

More about ATRAP

ALPHA makes, captures and studies atoms of antihydrogen and compares them with hydrogen atoms

ALPHA

ALPHA makes, captures and studies atoms of antihydrogen and compares them with hydrogen atoms

More about ALPHA

ASACUSA compares matter and antimatter using atoms of antiprotonic helium

ASACUSA

ASACUSA compares matter and antimatter using atoms of antiprotonic helium

More about ASACUSA

Featured updates on this topic

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!

Updates

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

12 Feb 2013 – An international team of collaborators are manipulating 'fat' antiatoms at the AEGIS experiment at CERN's Antiproton Decelerator

29 Jan 2013 – The recently installed AEGIS experiment will examine the effect of gravity on antimatter

15 Jan 2013 – At CERN today, the experiments at the Antiproton Decelerator presented updates on their work in 2012, and their hopes for 2013