Check your privilege with an antimatter beam

In a sense, antimatter beams are commonplace. The Tevatron machine at Fermilab in Chicago had the best beam of antiprotons, and used it to find the top quark. The LEP collider, which between 1990 and 2000 sat in the tunnel at CERN now occupied by the Large Hadron Collider, had a beam of positrons - the antiparticle of the electron. However, proper matter, everyday matter, is made of atoms. That is, electrons bound to an atomic nucleus. Slowing positrons and antiprotons down and making them stick together into anti-atoms of antihydrogen is difficult.

If you can do it, the rewards are substantial though. With a big enough sample of anti-hydrogen, one can make detailed studies of the energy levels that the positron can occupy in its journey around the antiproton. These energy levels have been measured very precisely for hydrogen, and the expectation is that they should be identical in antihydrogen. But we won’t know until we look.

The ALPHA experiment at CERN made a start on this almost exactly two years ago, with a rough first measurement. They will be more precise in the future. But one of the problems with precision in these experiments is that you need big magnetic fields to traps the anti-atoms, stop them meeting atoms, and annihilating. Unfortunately these magnetic fields also distort the energy levels, and will likely in the end limit the precision of any comparison to hydrogen.

The ASACUSA experiment plans to get around that by making a beam of antimatter, and measuring the energy levels as the beam travels in a vacuum, away from the magnetic fields and away from any nasty annihilating matter. They published a paper on it in January and there is a nice article in the CERN courier this week giving some more details of the technique and how they plan to develop it.

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http://www.theguardian.com/science/life-and-physics/2014/mar/01/check-your-privilege-with-an-antimatter-beam