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Register a new userTowards a high-precision measurement of the antiproton magnetic moment
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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.
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DeclareRobustCommand{pbar}{HepAntiParticle{p}{}{}xspace} DeclareRobustCommand{p}{HepParticle{p}{}{}xspace} DeclareRobustCommand{mup}{$mu_{p}${}{}xspace} DeclareRobustCommand{mupbar}{$mu_{pbar}${}{}xspace} DeclareRobustCommand{muN}{$mu_N${}{}xspace For the first time a single trapped pbar is used to measure the pbar magnetic moment ${bmmu}_{pbar}$. The moment ${bmmu}_{pbar} = mu_{pbar} {bm S}/(hbar/2)$ is given in terms of its spin ${bm S}$ and the nuclear magneton (muN) by $mu_{pbar}/mu_N = -2.792,845 pm 0.000,012$. The 4.4 parts per million (ppm) uncertainty is 680 times smaller than previously realized. Comparing to the proton moment measured using the same method and trap electrodes gives $mu_{pbar}/mu_p = -1.000,000 pm 0.000,005$ to 5 ppm, for a proton moment ${bm{mu}}_{p} = mu_{p} {bm S}/(hbar/2)$, consistent with the prediction of the CPT theorem.
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 protons cyclotron frequency is used to determine the magnetic field of the trap. From the normalized resonance curve, we extract the particles 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.
We report precision measurements of the nuclear magnetic moment of textsuperscript{43}Catextsuperscript{+}, made by microwave spectroscopy of the 4s $^2$S$_{1/2}$ $left|F=4, M=0rightrangle rightarrow left|F=3, M=1rightrangle$ ground level hyperfine clock transition at a magnetic field of $approx$ 146 G, using a single laser-cooled ion in a Paul trap. We measure a clock transition frequency of $f = 3199941076.920 pm 0.046$ Hz, from which we determine $mu_I / mu_{rm{N}} = -1.315350(9)(1)$, where the uncertainty (9) arises from uncertainty in the hyperfine $A$ constant, and the (1) arises from the uncertainty in our measurement. This measurement is not corrected for diamagnetic shielding due to the bound electrons. We make a second measurement which is less precise but agrees with the first. We use our $mu_I$ value, in combination with previous NMR results, to extract the change in shielding constant of calcium ions due to solvation in D$_2$O: $Delta sigma = -0.00022(1)$.
We describe the first precision measurement of the electrons electric dipole moment (eEDM, $d_e$) using trapped molecular ions, demonstrating the application of spin interrogation times over 700 ms to achieve high sensitivity and stringent rejection of systematic errors. Through electron spin resonance spectroscopy on $^{180}{rm Hf}^{19}{rm F}^{+}$ in its metastable $^{3}Delta_{1}$ electronic state, we obtain $d_e = (0.9 pm 7.7_{rm stat} pm 1.7_{rm syst}) times 10^{-29},e,{rm cm}$, resulting in an upper bound of $|d_e| < 1.3 times 10^{-28},e,{rm cm}$ (90% confidence). Our result provides independent confirmation of the current upper bound of $|d_e| < 9.3 times 10^{-29},e,{rm cm}$ [J. Baron $textit{et al.}$, Science $textbf{343}$, 269 (2014)], and offers the potential to improve on this limit in the near future.
The cesium 6S_1/2 scalar dipole polarizability alpha_0 has been determined from the time-of-flight of laser cooled and launched cesium atoms traveling through an electric field. We find alpha_0 = 6.611+-0.009 x 10^-39 C m^2/V= 59.42+-0.08 x 10^-24 cm^3 = 401.0+-0.6 a_0^3. The 0.14% uncertainty is a factor of fourteen improvement over the previous measurement. Values for the 6P_1/2 and 6P_3/2 lifetimes and the 6S_1/2 cesium-cesium dispersion coefficient C_6 are determined from alpha_0 using the procedure of Derevianko and Porsev [Phys. Rev. A 65, 053403 (2002)].
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