Researchers have trapped and held the atoms, the anti-matter counterpart of hydrogen, using an experiment called ALPHA at CERN in Switzerland. Anti-matter particles are instantly annihilated when they come into contact with matter and, until now, it has not been possible to study anti-hydrogen in any detail. The experiment has brought scientists closer to understanding the structure and composition of anti-matter.
The ALPHA experiment was developed to cool and slow down the anti-particles that make up anti-hydrogen and mix them to produce antihydrogen. Some of the anti-atoms are then trapped by electromagnets inside the machine, giving researchers the time to study them. Liverpool scientists constructed the silicon detector system at the heart of the experiment to identify when anti-hydrogen is present inside the experiment.
Professor Paul Nolan, from the University of Liverpool's Department of Physics, explains: "When antihydrogen decays inside the ALPHA experiment, it emits particles, called pions, from the point at which it exists. Our detector surrounds the area where antihydrogen is formed and for each pion emitted we get three points as it travels outwards. Using a computer we can then construct a line between these points and trace it back to the origin of the antihydrogen. Being able to study these particles brings us closer to understanding the composition of anti-matter and the physical properties of our Universe."
Particles that are known to exist in the Universe have their mirror image in anti-matter, but with the opposite electrical charge. It is thought that when the Universe formed, matter and anti-matter existed in equal measure, until they collided and annihilated, with the residual matter making up the planets of the solar system. Although anti-matter is known to exist - in the stars for example - scientists have questioned for many year why it is only matter that can be seen in our physical world today.
Professor Mike Charlton, at Swansea University, added: "Hydrogen is the simplest of all atoms, and antihydrogen is the easiest type of anti-matter to produce in the laboratory. Understanding it will hopefully enable us to shed light on why almost everything in the known Universe consists of matter, rather than anti-matter."
The work is published in Nature and supported by the Engineering and Physical Sciences Research Council (EPSRC).
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