Carbon Based

Posts tagged spin

16 notes

Lonely, spun-out proton reveals magnetic secret

22 April 2011 by Mark Buchanan

AN ISOLATED proton has been trapped and coaxed into revealing the strength of its magnetism, a feat that could help investigate an enduring question about antimatter.

Many subatomic particles act like tiny magnets, with their strength dubbed their “g-factor”. Prior attempts to measure the proton’s g-factor were not precise as they were restricted to probing protons in atoms, where orbiting electrons disguise the proton’s properties.

Now physicists led by Jochen Walz at the University of Mainz in Germany have managed to isolate a single proton and measure its g-factor. They start by shooting electrons at a substance: the impact releases protons, which can be trapped using a magnet. Next, the researchers slowly let the protons escape until just one is left. The magnet causes the lone proton to “precess” like a spinning top, at a frequency that depends on its g-factor. The researchers deduced this frequency using radio waves that flipped the orientation of the proton’s magnet only when their frequency matched the precession frequency (arxiv.org/abs/1104.1206v1).

This in itself did not yield a more precise value for the g-factor than previously, but it will if the proof-of-principle experiment is repeated using a higher-precision trap, says Wolfgang Quint, a team member from the Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany.

The technique could also be used to measure the g-factor of antiprotons. It is thought that antimatter is a mirror image of matter - exactly the same but with an opposite charge. If this is true, then the g-factors of the proton and antiproton should be identical.

Filed under magnetism particle physics universe proton antiproton antimatter magnetism spin