Towards a high-precision measurement of the antiproton magnetic moment

The recent observation of single spins flips with a single proton in a Penning trap opens the way to measure the proton magnetic moment with high precision. Based on this success, which has been achieved with our apparatus at the University of Mainz, we demonstrated recently the first application of the so called double Penning-trap method with a single proton. This is a major step towards a measurement of the proton magnetic moment with ppb precision. To apply this method to a single trapped antiproton our collaboration is currently setting up a companion experiment at the antiproton decelerator of CERN. This effort is recognized as the Baryon Antibaryon Symmetry Experiment (BASE). A comparison of both magnetic moment values will provide a stringent test of CPT invariance with baryons.Comment: Submitted to LEAP 2013 conference proceeding

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

Q value and half-life of double-electron capture in Os-184

Os-184 has been excluded as a promising candidate for the search of neutrinoless double-electron capture. High-precision mass measurements with the Penning-trap mass spectrometer TRIGA-TRAP resulted in a marginal resonant enhancement with = -8.89(58) keV excess energy to the 1322.152(22) keV 0+ excited state in W-184. State-of-the-art energy density functional calculations are applied for the evaluation of the nuclear matrix elements to the excited states predicting a strong suppression due to the large deformation of mother and daughter states. The half-life of the transition in Os-184 exceeds T_{1/2} > 1.3 10^{29} years for an effective neutrino mass of 1 eV.Comment: accepted in Phys. Rev.

Position-sensitive ion detection in precision Penning trap mass spectrometry

A commercial, position-sensitive ion detector was used for the first time for the time-of-flight ion-cyclotron resonance detection technique in Penning trap mass spectrometry. In this work, the characteristics of the detector and its implementation in a Penning trap mass spectrometer will be presented. In addition, simulations and experimental studies concerning the observation of ions ejected from a Penning trap are described. This will allow for a precise monitoring of the state of ion motion in the trap.Comment: 20 pages, 13 figure

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

Sixfold improved single particle measurement of the magnetic moment of the antiproton

Our current understanding of the Universe comes, among others, from particle physics and cosmology. In particle physics an almost perfect symmetry between matter and antimatter exists. On cosmological scales, however, a striking matter/antimatter imbalance is observed. This contradiction inspires comparisons of the fundamental properties of particles and antiparticles with high precision. Here we report on a measurement of the g-factor of the antiproton with a fractional precision of 0.8 parts per million at 95% confidence level. Our value /2=2.7928465(23) outperforms the previous best measurement by a factor of 6. The result is consistent with our proton g-factor measurement gp/2=2.792847350(9), and therefore agrees with the fundamental charge, parity, time (CPT) invariance of the Standard Model of particle physics. Additionally, our result improves coefficients of the standard model extension which discusses the sensitivity of experiments with respect to CPT violation by up to a factor of 20.EU/ERC/290870-MEFUCOMax-Planck SocietyHelmholtz-GemeinschaftRIKEN Initiative Research Unit ProgramRIKEN President FundingRIKEN Pioneering Project FundingRIKEN FPR FundingRIKEN JRA ProgramMEXT/24000008Max-Planck SocietyEU/ERC Advanced Grant/290870-MEFUCOHelmholtz-GemeinschaftCERN-fellowship program

Improved limit on the directly measured antiproton lifetime

Continuous monitoring of a cloud of antiprotons stored in a Penning trap for 405 days enables us to set an improved limit on the directly measured antiproton lifetime. From our measurements we extract a storage time of 3.15x108 equivalent antiproton-seconds, resulting in a lower lifetime limit of Tp > 10.2,a with a confidence level of 68%. This result improves the limit on charge-parity-time violation in antiproton decays based on direct observation by a factor of 7

A 16 Parts per Trillion Comparison of the Antiproton-to-Proton q/m Ratios

The Standard Model (SM) of particle physics is both incredibly successful and glaringly incomplete. Among the questions left open is the striking imbalance of matter and antimatter in the observable universe which inspires experiments to compare the fundamental properties of matter/antimatter conjugates with high precision. Our experiments deal with direct investigations of the fundamental properties of protons and antiprotons, performing spectroscopy in advanced cryogenic Penning-trap systems. For instance, we compared the proton/antiproton magnetic moments with 1.5 ppb fractional precision, which improved upon previous best measurements by a factor of >3000. Here we report on a new comparison of the proton/antiproton charge-to-mass ratios with a fractional uncertainty of 16ppt. Our result is based on the combination of four independent long term studies, recorded in a total time span of 1.5 years. We use different measurement methods and experimental setups incorporating different systematic effects. The final result, $-(q/m)_{\mathrm{p}}/(q/m)_{\bar{\mathrm{p}}}$ = $1.000\,000\,000\,003 (16)$, is consistent with the fundamental charge-parity-time (CPT) reversal invariance, and improves the precision of our previous best measurement by a factor of 4.3. The measurement tests the SM at an energy scale of $1.96\cdot10^{-27}\,$GeV (C$.$L$.$ 0.68), and improves 10 coefficients of the Standard Model Extension (SME). Our cyclotron-clock-study also constrains hypothetical interactions mediating violations of the clock weak equivalence principle (WEP$_\text{cc}$) for antimatter to a level of $|\alpha_{g}-1| < 1.8 \cdot 10^{-7}$, and enables the first differential test of the WEP$_\text{cc}$ using antiprotons \cite{hughes1991constraints}. From this interpretation we constrain the differential WEP$_\text{cc}$-violating coefficient to $|\alpha_{g,D}-1|<0.030$