Liverpool scientists trap antimatter at ALPHA experiment

From l to r: Nicholas Lockwood, Prof Simon Maskell, Dr Alex Phillips and Andre Finn.


Physicists at the Universities of Liverpool and Swansea have succeeded in trapping atoms of antimatter for more than 16 minutes, long enough to begin to study their properties in detail.

Antimatter was trapped using an experiment called ALPHA, part of a broad programme at CERN’s antiproton decelerator investigating the mysteries of one of nature’s most elusive substances. ALPHA uses a silicon vertex detector which was designed, commissioned, and built in the Liverpool Semiconductor Detector Centre.

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 years why it is only matter that can be seen in our physical world today.

Professor Paul Nolan from the Department of Physics , who leads the Liverpool team, said: “Our aim is to study antihydrogen, and make detailed comparisons with ordinary hydrogen. Whilst hydrogen is the most abundant element in the Universe, it seems that antihydrogen has only ever been formed in our experiments here on Earth. Why there was no antimatter left when the Universe became cold enough for atoms to form remains a great mystery, and one we hope to shed some light upon.”

Scientists have studied 300 trapped antiatoms, which will allow antihydrogen to be mapped and compared to the hydrogen atom. Any difference should become apparent under careful analysis. Trapping antiatoms could also provide a complementary approach to measuring the influence of gravity on antimatter, which will soon be investigated with antihydrogen by the AEgIS experiment.

The next step for ALPHA is to start performing measurements on trapped antihydrogen, and this is due to get underway later this year. The first step is to illuminate the trapped anti-atoms with microwaves and determine if they absorb exactly the same frequencies, or energies, as matter.

The work is published in Nature and supported by the Engineering and Physical Sciences Research Council (EPSRC).

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