Comparison of the Antiproton to Proton Charge to Mass Ratio

In a paper published today in Nature we report the high-precision comparison of the antiproton-to-proton charge to mass ratio. In our measurements we compared the cyclotron frequencies of antiprotons to that of negatively charged hydrogen ions, which are used as a proxy for the proton. We achieved a fractional precision of 69 parts in a trillion, which corresponds in our magnetic field of 1.95 Tesla to an absolute energy resolution of 2mHz. Our result is consistent with CPT invariance.

WELCOME

 

BASE is a multinational collaboration at the Antiproton Decelerator (AD) of CERN which aims at precise comparisons of antiproton and proton magnetic g-factors. Such comparisons are interesting because any measured asymmetry would hint at physics beyond the Standard Model. The experiment consists of measuring the cyclotron and Larmor frequencies of a single trapped (anti)proton. By measuring the ratio of these two frequencies the magnetic moment of the (anti)proton is obtained in units of the nuclear magneton. The BASE collaboration observed the first spin flips with a single trapped proton, measured the magnetic moment of the proton with a fractional precision at the ppm level, observed first single proton spin filps and demonstrated the double Penning trap technique for the first time. Very recently, we performed the first direct high-precision measurement of the magnetic moment of a single trapped proton. Our value has a precision of 3.3 ppb, outperforms previous Penning trap experiments by a factor of 760, and improves the currently acceped CODATA literature value by a factor of 2.5. By applying this technique to the antiproton magnetic moment a 1000-fold improvement of precision is possible, which will provide one of the most sensitive tests of CPT invariance ever performed.

IUPAP Prize 2014

BASE member Stefan Ulmer has been selected to receive the IUPAP Young Scientist Prize 2014 in Fundamental Metrology. With this prize the International Union of Pure and Applied Physics (IUPAP) honors his work on proton and antiproton magnetic moment measurements.

First Direct High Precision Measurement of the Proton Magnetic Moment

In a paper just published in Nature we report on the first direct high precision measurement of the proton magnetic moment. By application of the elegant double Penning trap technique we achieved a fractional precision of 3.3 parts per billion. Our value is consistent with the currently accepted CODATA value, but 2.5 times more precise.

Demonstration of the Double Penning Trap Technique

In a just in Physics Letters B published article we report on the first successful demonstration of the double Penning trap technique with a single proton. This is a major step towards a  measurement of the particle's magnetic moment with ppb precision. The method can be applied to the antiproton, which will enable one of the most sensitive tests of CPT symmetry with baryons.

CERN SPSC Recommends BASE Approval

The BASE technical design report was evaluated by the SPSC. The committee recommended approval of the BASE project to the research board. Our TDR contains a detailed description of our experiment and a feasibility study for implementation of BASE into the Antiproton Decelerator facility. We acknowledge the strong support of the CERN groups which contributed to to this study.Special thanks to Lajos Bojtar for the coordination.

First Resolution of Single Spin Flips with a Single Proton

In a just in Physical Review Letters published article we report on the first detection of single spin-flips of a single proton. We use Bayesian analysis methods and obtain spin state detection fidelities close to 100%. This is a major step towards the application of the so-called double Penning-trap method to measure magnetic moments of both the proton and the antiproton with ppb precision.

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