BASE experiment

Short description: Multinational collaboration

official BASE logo

BASE (Baryon Antibaryon Symmetry Experiment), AD-8, is a multinational collaboration at the Antiproton Decelerator facility at CERN, Geneva. The goal of the Japanese and German BASE collaboration[1] are high-precision investigations of the fundamental properties of the antiproton, namely the charge-to-mass ratio and the magnetic moment.

## Contents

* 1 Experimental setup
* 2 BASE physics
* 3 BASE collaboration
* 4 See also
* 5 References
* 6 External links

## Experimental setup

The single antiprotons are stored in an advanced Penning trap system, which has a multi-trap system at its core. It consists of a reservoir trap,[2] a precision trap, an analysis trap and a cooling trap. The reservoir trap has the capability to store antiprotons for several years[3] and allows BASE to operate experiments independent from accelerator cycles. The precision trap is for high precision frequency measurements, and the analysis trap has a strong magnetic field inhomogeneity superimposed, which is used for single particle spin flip spectroscopy. By measuring the spin flip rate as a function of the frequency of an externally applied magnetic-drive, a resonance curve is obtained. Together with a measurement of the cyclotron frequency, the magnetic moment is extracted.

## BASE physics

The BASE collaboration developed techniques to observe the first spin flips of a single trapped proton[4] and applied the double-trap technique to measure the magnetic moment of the proton with a fractional precision of three parts in a billion,[5] later improved to a precision of 300 parts in a trillion, [6] being the most precise measurement of this fundamental property of the proton. With the invention of a two particle/three trap technique BASE measured the antiproton magnetic moment with a fractional accuracy of 1.5 parts in a billion, which improved the previous most precise proton/antiproton comparison in that sector [7] by more than a factor of 3000. This measurement constitutes one of the most stringent tests of CPT invariance with baryons to date, and sets the most stringent limits on antimatter/dark matter interaction to date.[8]

Inspired by this work BASE has also used Penning trap detectors as axion haloscopes, and derived stringent narrow-band laboratory limits on the conversion of axions to photons.[9]

In 2022 BASE measured that the charge-to-mass ratios of protons and antiprotons are equal within a precision of 16 parts per trillion.[10][11] This measurement constitutes the most precise test of CPT invariance in the baryon sector and sets the first differential constraints on the clock weak equivalence principle using baryonic antimatter.

## BASE collaboration

Views of the BASE experimental zone

Views of the BASE experimental zone

The BASE collaboration comprises the following institutions:

## See also

1. Antiproton Decelerator
2. TRAP experiment
3. ATRAP experiment

## References

1. ↑ "official BASE website". http://base.web.cern.ch.
2. ↑ Smorra, C.; Mooser, A.; Franke, K.; Nagahama, H.; Schneider, G.; Higuchi, T.; Gorp, S. V.; Blaum, K. et al. (2015-10-15). "A reservoir trap for antiprotons" (in en). International Journal of Mass Spectrometry 389: 10–13. doi:10.1016/j.ijms.2015.08.007. ISSN 1387-3806. https://www.sciencedirect.com/science/article/pii/S1387380615002560.
3. ↑ Sellner, S; Besirli, M; Bohman, M; Borchert, M J; Harrington, J; Higuchi, T; Mooser, A; Nagahama, H et al. (2017-08-31). "Improved limit on the directly measured antiproton lifetime" (in en). New Journal of Physics 19 (8): 083023. doi:10.1088/1367-2630/aa7e73. ISSN 1367-2630. https://iopscience.iop.org/article/10.1088/1367-2630/aa7e73.
4. ↑ Ulmer, S. (20 June 2011). "Observation of Spin Flips with a Single Trapped Proton". Physical Review Letters 106 (25): 253001. doi:10.1103/PhysRevLett.106.253001. PMID 21770638. Bibcode: 2011PhRvL.106y3001U.
5. ↑ Mooser, A. (2014). "Direct high-precision measurement of the magnetic moment of the proton". Nature 509 (7502): 596–599. doi:10.1038/nature13388. PMID 24870545. Bibcode: 2014Natur.509..596M.
6. ↑ Schneider, Georg; Mooser, Andreas; Bohman, Matthew; Schön, Natalie; Harrington, James; Higuchi, Takashi; Nagahama, Hiroki; Sellner, Stefan et al. (2017-11-24). "Double-trap measurement of the proton magnetic moment at 0.3 parts per billion precision" (in en). Science 358 (6366): 1081–1084. doi:10.1126/science.aan0207. ISSN 0036-8075. PMID 29170238. https://www.sciencemag.org/lookup/doi/10.1126/science.aan0207.
7. ↑ ATRAP Collaboration; DiSciacca, J.; Marshall, M.; Marable, K.; Gabrielse, G.; Ettenauer, S.; Tardiff, E.; Kalra, R. et al. (2013-03-25). "One-Particle Measurement of the Antiproton Magnetic Moment". Physical Review Letters 110 (13): 130801. doi:10.1103/PhysRevLett.110.130801. PMID 23581304. https://link.aps.org/doi/10.1103/PhysRevLett.110.130801.
8. ↑ ATRAP Collaboration; DiSciacca, J.; Marshall, M.; Marable, K.; Gabrielse, G.; Ettenauer, S.; Tardiff, E.; Kalra, R. et al. (2013-03-25). "One-Particle Measurement of the Antiproton Magnetic Moment". Physical Review Letters 110 (13): 130801. doi:10.1103/PhysRevLett.110.130801. PMID 23581304. https://link.aps.org/doi/10.1103/PhysRevLett.110.130801.
9. ↑ Devlin, Jack A.; Borchert, Matthias J.; Erlewein, Stefan; Fleck, Markus; Harrington, James A.; Latacz, Barbara; Warncke, Jan; Wursten, Elise et al. (2021-01-25). "Constraints on the Coupling between Axionlike Dark Matter and Photons Using an Antiproton Superconducting Tuned Detection Circuit in a Cryogenic Penning Trap". Physical Review Letters 126 (4): 041301. doi:10.1103/PhysRevLett.126.041301. PMID 33576660. https://link.aps.org/doi/10.1103/PhysRevLett.126.041301.
10. ↑ Borchert, M. J.; Devlin, J. A.; Erlewein, S. R.; Fleck, M.; Harrington, J. A.; Higuchi, T.; Latacz, B. M.; Voelksen, F. et al. (2022-01-06). "A 16-parts-per-trillion measurement of the antiproton-to-proton charge–mass ratio" (in en). Nature 601 (7891): 53–57. doi:10.1038/s41586-021-04203-w. ISSN 0028-0836. PMID 34987217. https://www.nature.com/articles/s41586-021-04203-w.
11. ↑ "BASE breaks new ground in matter–antimatter comparisons" (in en). http://home.cern/news/news/physics/base-breaks-new-ground-matter-antimatter-comparisons.

## External links

Record for BASE Experiment on INSPIRE-HEP

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