Direct Measurement of the Proton Magnetic Moment

Abstract

The proton magnetic moment in nuclear magnetons is measured to be μ(p)/μ(N) ≡ g/2 = 2.792 846 ± 0.000 007, a 2.5 parts per million uncertainty. The direct determination, using a single proton in a Penning trap, demonstrates the first method that should work as well with an antiproton (p) as with a proton (p). This opens the way to measuring the p magnetic moment (whose uncertainty has essentially not been reduced for 20 years) at least 10(3) times more precisely.

Electron g‐factor determinations in Penning traps

“…The small size of the proton's magnetic moment, however, makes it technically more challenging. Experiments are under way at the University of Mainz [71] and at Harvard University [72], as well as at CERN for the antiproton [73,74]. Both have very recently produced first data and an improvement of the relative precision to the anticipated 10 −9 is foreseeable for the close future.…”

One-Particle Measurement of the Antiproton Magnetic Moment

“…1). The methods and apparatus were initially demonstrated in a one-proton measurement of p [6], following the realization of feedback cooling and a self-excited oscillator with one proton [7]. We profited from a parallel exploration of proton spin flips [8] and a measurement of p [9] that followed ours.…”

The Production and Study of Cold Antiprotons and Antihydrogen

“…Hopes are high for a greatly improved comparison of the magnetic moments of the antiproton and proton since we managed make the first one-particle comparison [38,40] and then to detect the spin flips of a trapped proton [44] (as discussed). It should also be possible to make the new apparatus capable of a measurement of q/m for the p that improves significantly our 9 parts in 10 11 measurement [17] -currently the best baryon CPT test.…”