Eur. Phys. J. Special Topics 224, 3055-3108 (2015)
https://doi.org/10.1140/epjst/e2015-02607-4

Review

BASE – The Baryon Antibaryon Symmetry Experiment

¹ Ulmer Initiative Research Unit, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
² CERN, 1211 Geneva 23, Switzerland
³ Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
⁴ Institute of Quantum Optics, Leibniz Universität Hannover, Welfengarten 1, 30167 Hannover, Germany
⁵ Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
⁶ Helmholtz-Institut Mainz, 55099 Mainz, Germany
⁷ Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
⁸ Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
⁹ GSI-Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany
¹⁰ Ruprecht-Karls-Universität Heidelberg, 69047 Heidelberg, Germany
¹¹ Atomic Physics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan

^a e-mail: Christian.Smorra@cern.ch

Received: 21 September 2015
Revised: 1 October 2015
Published online: 23 November 2015

Abstract

The Baryon Antibaryon Symmetry Experiment (BASE) aims at performing a stringent test of the combined charge parity and time reversal (CPT) symmetry by comparing the magnetic moments of the proton and the antiproton with high precision. Using single particles in a Penning trap, the proton/antiproton g-factors, i.e. the magnetic moment in units of the nuclear magneton, are determined by measuring the respective ratio of the spin-precession frequency to the cyclotron frequency. The spin precession frequency is measured by non-destructive detection of spin quantum transitions using the continuous Stern-Gerlach effect, and the cyclotron frequency is determined from the particle*s motional eigenfrequencies in the Penning trap using the invariance theorem. By application of the double Penning-trap method we expect that in our measurements a fractional precision of δg/g 10⁻⁹ can be achieved. The successful application of this method to the antiproton will consist a factor 1000 improvement in the fractional precision of its magnetic moment. The BASE collaboration has constructed and commissioned a new experiment at the Antiproton Decelerator (AD) of CERN. This article describes and summarizes the physical and technical aspects of this new experiment.