Resolution of Single Spin-Flips of a Single Proton

The spin magnetic moment of a single proton in a cryogenic Penning trap was coupled to the particle's axial motion with a superimposed magnetic bottle. Jumps in the oscillation frequency indicate spin-flips and were identified using a Bayesian analysis.Comment: accepted for publication by Phys. Rev. Lett., submitted 6.June.201

Demonstration of the Double Penning Trap Technique with a Single Proton

Spin flips of a single proton were driven in a Penning trap with a homogeneous magnetic field. For the spin-state analysis the proton was transported into a second Penning trap with a superimposed magnetic bottle, and the continuous Stern-Gerlach effect was applied. This first demonstration of the double Penning trap technique with a single proton suggests that the antiproton magnetic moment measurement can potentially be improved by three orders of magnitude or more

The magnetic moments of the proton and the antiproton

Recent exciting progress in the preparation and manipulation of the motional quantum states of a single trapped proton enabled the first direct detection of the particle's spin state. Based on this success the proton magnetic moment $\mu_p$ was measured with ppm precision in a Penning trap with a superimposed magnetic field inhomogeneity. An improvement by an additional factor of 1000 in precision is possible by application of the so-called double Penning trap technique. In a recent paper we reported the first demonstration of this method with a single trapped proton, which is a major step towards the first direct high-precision measurement of $\mu_p$. The techniques required for the proton can be directly applied to measure the antiproton magnetic moment $\mu_{\bar{p}}$. An improvement in precision of $\mu_{\bar{p}}$ by more than three orders of magnitude becomes possible, which will provide one of the most sensitive tests of CPT invariance. To achieve this research goal we are currently setting up the Baryon Antibaryon Symmetry Experiment (BASE) at the antiproton decelerator (AD) of CERN

Direct high-precision measurement of the magnetic moment of the proton

The spin-magnetic moment of the proton $\mu_p$ is a fundamental property of this particle. So far $\mu_p$ has only been measured indirectly, 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 units of the nuclear magneton $\mu_p=2.792847350(9)\mu_N$. 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 $\mu_p$, by a factor of 3. By application of this method to the antiproton magnetic moment $\mu_{\bar{p}}$ the fractional precision of the recently reported value can be improved by a factor of at least 1000. Combined with the present result, this will provide a stringent test of matter/antimatter symmetry with baryons.Comment: published in Natur

Entrepreneurial Activity in the Context of Violent Conflict: Business and Organized Violence in Colombia1

"The Colombian private sector has been accused of promoting or profiting from violence in the country. However, the private sector's role in the violent conflict and the impact of conflict on economic and entrepreneurial activity vary, as reflected by differences in political activism in peacebuilding strategies and in costs endured according to company size, sector, and region of operations. At the same time, accounts of regional variation in conflict intensity suggest that an understanding of the Colombian context of violent conflict requires a subnational approach. This paper explores whether and how differences in regional violent conflict can be attributed to the make-up of economic organizations and entrepreneurial activity associated with the production of five natural resources (oil, coffee, bananas, emeralds, and flowers) in several Colombian regions. It is found that company-specific traits, institutions of production, and the nature of international markets have a significant impact on the link between entrepreneurial activity and regional and local dynamics of the violent conflict in Colombia. © 2011, Copyright CCSBE/CCPME.

Entrepreneurial Activity in the Context of Violent Conflict: Business and Organized Violence in Colombia1

The Colombian private sector has been accused of promoting or profiting from violence in the country. However, the private sector's role in the violent conflict and the impact of conflict on economic and entrepreneurial activity vary, as reflected by differences in political activism in peacebuilding strategies and in costs endured according to company size, sector, and region of operations. At the same time, accounts of regional variation in conflict intensity suggest that an understanding of the Colombian context of violent conflict requires a subnational approach. This paper explores whether and how differences in regional violent conflict can be attributed to the make-up of economic organizations and entrepreneurial activity associated with the production of five natural resources (oil, coffee, bananas, emeralds, and flowers) in several Colombian regions. It is found that company-specific traits, institutions of production, and the nature of international markets have a significant impact on the link between entrepreneurial activity and regional and local dynamics of the violent conflict in Colombia. © 2011, Copyright CCSBE/CCPME