Accurate Measurement of the Antiproton Magnetic Moment

Using Quantum Jump Spectroscopy

Our antiproton proposal: a million-fold improved comparison of antiproton and proton magnetic moments,
to make one of the most precise baryon CPT tests

To measure a proton or antiproton magnetic moment: measure a cyclotron frequency and a spin-flip frequency  


  • antiproton moment (~nuclear magneton) << electron magnetic moment (~Bohr magneton)
  • therefore about 1000 times harder to observe

  • Goal 1: Nondestructive observations of the spin flips of a single trapped proton
  • Goal 2: Measurement of a proton spin resonance using quantum jump spectroscopy
  • Goal 3: Determine the magnetic moment of the proton from measured spin and cyclotron frequencies
  • Goal 4: Load antiprotons into the trap and duplicate goals 1 to 3 with a single trapped antiproton
  • Goal 5: Compare the antiproton and proton magnetic moments a million or more times more accurately

  Demonstrate the first one-proton self-excited oscillator to get the needed detection resolution to see a spin flip.  (Method equally applicable to one antiproton.)

What We Are Doing

Observing the spin flip of a single isolated proton is the PhD thesis project of Nick Guise. This is much harder than is observing the spin flip of a single isolated electron which our group has done on the way to measuring the electron magnetic moment to an accuracy of 3 parts in 1013. As part of his PhD thesis Jack DiSciacca is beginning to make an apparatus into which we can load an antiproton at CERN.

Return to Gabrielse group home page
Printable narrative of Gabrielse group results (pdf, doc)
See our latest apparatus and progress