Chief Scientist Laboratories Fundamental Symmetries Laboratory

Chief Scientist: Stefan Ulmer (Dr. rer. nat)

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Research Summary

The Ulmer Fundamental Symmetries Laboratory is leading the BASE collaboration at the antiproton decelerator of CERN, Geneva, Switzerland. Our goal is to perform high-precision comparisons of the fundamental properties, such as magnetic moments and charge-to-mass ratios, of the proton and the antiproton. Our measurements provide stringent tests of CPT invariance, which is the most fundamental symmetry in the Standard Model of Particle Physics. To this end, we have developed the advanced Penning trap system BASE. With our experiments we have performed the most precise test of CPT invariance in the baryon-sector by comparing the antiproton-to-proton charge-to-mass ratio with a fractional precision of 69 parts in a trillion, the most precise measurement of the proton magnetic moment with a fractional precision of 3.3ppb, as well as the most precise measurement of the antiproton magnetic moment with a fractional precision of 0.8 ppm. Currently, we are implementing the double-Penning-trap technique to improve the precision of the antiproton magnetic moment measurement by at least a factor of 100. A major step towards this goal, the observation of single antiproton spin transitions with high fidelity, has recently been achieved.

In addition to BASE, the Ulmer Fundamental Symmetries Laboratory is involved in the ASACUSA-CUSP experiment. Here we aim at a high precision measurement of the hyperfine structure of antihydrogen. In this experiment we succeeded in producing a beam of antihydrogen atoms, which is a major step towards the planned spectroscopy. Moreover, the Ulmer lab takes part in a Max-Planck/RIKEN collaboration to measure the mass of the proton in natural units with improved precision.

Main Research Fields

Physics

Research Subjects

High-precision measurements of the fundamental properties of the proton and the antiproton
Percision measurement of the ground state hyperfine splitting of antihydrogen
Development of novel techniques for high-precision Penning trap experiments

Selected Publications

Papers with an asterisk(*) are based on research conducted outside of RIKEN.

1.G. Schneider, A. Mooser, M. Bohman, N. Schön, J. Harrington, T. Higuchi, H. Nagahama, S. Sellner, C. Smorra, K. Blaum, Y. Matsuda, W. Quint, J. Walz, S. Ulmer.:
“Double-trap measurement of the proton magnetic moment at 0.3 parts per billion precision”
Science Vol. 358, Issue 6366, pp. 1081-1084
2.C. Smorra, S. Sellner, M. J. Borchert, J. A. Harrington, T. Higuchi, H. Nagahama, T. Tanaka, A. Mooser, G. Schneider, M. Bohman, K. Blaum, Y. Matsuda, C. Ospelkaus, W. Quint, J. Walz, Y. Yamazaki and S. Ulmer.:
“A parts-per-billion measurement of the antiproton magnetic moment”
Nature 550, 371-374 (2017)
3.F. Heiße, F. Köhler-Langes, S. Rau, J. Hou, S. Junck, A. Kracke, A. Mooser, W. Quint, S. Ulmer, G. Werth, K. Blaum, and S. Sturm.:
“High-Precision Measurement of the Proton’s Atomic Mass”
Phys. Rev. Lett. 119, 033001 (2017)
4.Smorra C., Mooser A., Besirli M., Bohman M., Borchert M., Nagahama H., Schneider G., Higuchi T., Tanaka T., Sellner S., Blaum K., Matsuda Y., Ospelkaus C., Quint W., Walz J., Yamazaki Y., Ulmer, S.:
“Observation of individual spin quantum transitions of a single antiproton”
Phys. Lett. B 769, 1 (2017)
5.Nagahama H., Smorra C., Sellner S., Besirli M., Borchert M., Mooser A., Schneider G., Higuchi T., Tanaka T., Blaum K., Matsuda Y., Ospelkaus C., Quint W., Walz J., Yamazaki Y., Ulmer, S.:
“Sixfold Improved Single Particle Measurement of the Magnetic Moment of the Antiproton”
Nature Communications 8, 14084 (2017)
6.Ulmer S., Smorra C., Mooser A., Franke K., Nagahama H., Schneider G., Higuchi T., Van Gorp S., Blaum K., Matsuda Y., Quint W., Walz J. & Yamazaki Y.:
“High precision comparison of the antiproton to proton charge-to-mass ratio”
Nature 524, 196 (2015)
7.Smorra C., Mooser A., Franke K., Nagahama H., Schneider G., Higuchi T., Van Gorp S., Blaum K., Matsuda Y., Quint W., Walz J., Yamazaki Y. and Ulmer S.:
“A Reservoir Trap For Antiprotons”
Int. Journ. Mass. Spec. 389, 10 (2015)
8.*Mooser A., Ulmer S., Blaum K., Franke K., Kracke H., Leiteritz C., Quint W., Rodegheri C.C., Smorra C., Walz J.:
“Direct High-Precision Measurement of the Magnetic Moment of the Proton”
Nature 509, 596--599 (2014)
9.Kuroda N., Ulmer S., Murtagh D., Van Gorp S., Nagata Y., Diermaier M., Federmann S., Leali M., Malbrunot C., Mascagna V., Massiczek O., Michishio K., Mizutani T., Mohri A., Nagahama H., Ohtsuka M., Radics B., Sakurai S., Sauerzopf C., Suzuki K., Tajima M., Torii H. A., Venturelli L, Wuenschek B., Zmeskal J., Zurlo N., Higaki H., Kanai Y., Lodi Rizzini E., Nagashima Y., Matsuda Y, Widmann E., Yamazaki Y.:
“A source of antihydrogen for in-flight hyperfine spectroscopy”
Nature Communications 5, 3089 (2014)
10.*S. Ulmer, C. C. Rodegheri, H. Kracke, K. Blaum, A. Mooser, W. Quint, and J. Walz.:
“Observation of spin flips with a single trapped proton”
Phys. Rev. Lett. 106, 253001 (2011)