One-Particle Measurement of the Antiproton Magnetic Moment

DeclareRobustCommand{pbar}{HepAntiParticle{p}{}{}xspace} DeclareRobustCommand{p}{HepParticle{p}{}{}xspace} DeclareRobustCommand{mup}{$mu_{p}${}{}xspace} DeclareRobustCommand{mupbar}{$mu_{pbar}${}{}xspace} DeclareRobustCommand{muN}{$mu_N${}{}xspace For the first time a single trapped pbar is used to measure the pbar magnetic moment ${bmmu}_{pbar}$. The moment ${bmmu}_{pbar} = mu_{pbar} {bm S}/(hbar/2)$ is given in terms of its spin ${bm S}$ and the nuclear magneton (muN) by $mu_{pbar}/mu_N = -2.792,845 pm 0.000,012$. The 4.4 parts per million (ppm) uncertainty is 680 times smaller than previously realized. Comparing to the proton moment measured using the same method and trap electrodes gives $mu_{pbar}/mu_p = -1.000,000 pm 0.000,005$ to 5 ppm, for a proton moment ${bm{mu}}_{p} = mu_{p} {bm S}/(hbar/2)$, consistent with the prediction of the CPT theorem.

Trapped Antihydrogen in Its Ground State

Antihydrogen atoms are confined in an Ioffe trap for 15 to 1000 seconds -- long enough to ensure that they reach their ground state. Though reproducibility challenges remain in making large numbers of cold antiprotons and positrons interact, 5 +/- 1 simultaneously-confined ground state atoms are produced and observed on average, substantially more than previously reported. Increases in the number of simultaneously trapped antithydrogen atoms are critical if laser-cooling of trapped antihydrogen is to be demonstrated, and spectroscopic studies at interesting levels of precision are to be carried out.