title: Direct high-precision measurement of the magnetic moment of the proton.
abstract: One of the fundamental properties of the proton is its magnetic moment, µp. So far µp has been measured only indirectly, by analysing the spectrum of an atomic hydrogen maser in a magnetic field. Here we report the direct high-precision measurement of the magnetic moment of a single proton using the double Penning-trap technique. We drive proton-spin quantum jumps by a magnetic radio-frequency field in a Penning trap with a homogeneous magnetic field. The induced spin transitions are detected in a second trap with a strong superimposed magnetic inhomogeneity. This enables the measurement of the spin-flip probability as a function of the drive frequency. In each measurement the proton's cyclotron frequency is used to determine the magnetic field of the trap. From the normalized resonance curve, we extract the particle's magnetic moment in terms of the nuclear magneton: μp = 2.792847350(9)μN. This measurement outperforms previous Penning-trap measurements in terms of precision by a factor of about 760. It improves the precision of the forty-year-old indirect measurement, in which significant theoretical bound state corrections were required to obtain µp, by a factor of 3. By application of this method to the antiproton magnetic moment, the fractional precision of the recently reported value can be improved by a factor of at least 1,000. Combined with the present result, this will provide a stringent test of matter/antimatter symmetry with baryons.
authors.affiliation: 1] Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany [2] Helmholtz-Institut Mainz, 55099 Mainz, Germany [3] RIKEN, Ulmer Initiative Research Unit, Wako, Saitama 351-0198, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Mooser
authors.affiliation: RIKEN, Ulmer Initiative Research Unit, Wako, Saitama 351-0198, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ulmer
authors.affiliation: Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Blaum
authors.affiliation: 1] RIKEN, Ulmer Initiative Research Unit, Wako, Saitama 351-0198, Japan [2] Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Franke
authors.affiliation: 1] Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany [2] Helmholtz-Institut Mainz, 55099 Mainz, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Kracke
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Leiteritz
authors.affiliation: 1] Fakultät für Physik und Astronomie, Ruprecht-Karls-Universität Heidelberg, 69047 Heidelberg, Germany [2] GSI-Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Quint
authors.affiliation: 1] Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany [2] Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany.
authors.forename: C C
authors.initials: CC
authors.lastname: Rodegheri
authors.affiliation: RIKEN, Ulmer Initiative Research Unit, Wako, Saitama 351-0198, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Smorra
authors.affiliation: 1] Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany [2] Helmholtz-Institut Mainz, 55099 Mainz, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Walz