The BASE collaboration: pushing the precision and cosmic frontiers of fundamental physics

by Jack Devlin (CERN)

Thursday 12 May 2022, 16:00 → 18:00 Australia/Sydney

I will discuss some of the recent work carried out at the BASE experiment at CERN, including new precision tests of fundamental symmetries and dark matter searches, and give an outlook of our future plans. 

BASE pushes the precision frontier by comparing the properties of antiprotons to protons with word-leading precision. Using a cryogenic Penning trap, we have conducted the most precise measurement of the proton-to-antiproton charge-to-mass ratio with a fractional uncertainty of 16 p.p.t. [1]. In other measurements, the collaboration measured the proton [2] and antiproton [3] magnetic moments, improving the precision of previous magnetic moment based tests of the fundamental CPT invariance [4] by more than a factor of 3000.

The ultra-sensitive methods necessary to perform measurements at this level of precision open up many possibilities for new physics searches, and in particular searches at the cosmic frontier for dark matter. In one analysis, BASE constrained the interactions between antiprotons with axion-like particles (ALPs) [5]. In another work [6], we investigated the noise spectrum of our image current detection circuits fixed-frequency resonant circuit for peaks caused by axion-to-photon conversion in the strong magnetic field of the Penning trap magnet. Our analysis using a fixed-frequency detector constrained the ALP-photon coupling to be gaγ<1×10−11 GeV−1 for ALPs with masses around 2.7906-2.7914 neV, and we have recently built a frequency tunable device to cover >2000 times broader mass range at improved sensitivity. Using our experience building high-Q resonant detectors, we are launching a new dedicated axion search project, BASE-CDM, to further investigate ALPs in the neV mass range.

[1] M. J. Borchert et al., Nature 601, 35 (2022).

[2] G. Schneider et al., Science 358, 1081 (2017).

[3] C. Smorra et al., Nature 550, 371 (2017).

[4] J. DiSciacca et al., Phys. Rev. Lett. 110, 130801 (2013).

[5] C. Smorra et al., Nature 575, 310 (2019).

[6] J. A. Devlin et al., Phys. Rev. Lett., accepted (2021).