# Challenging the Standard Model: High-Precision Comparisons of the Fundamental Properties of Protons and Antiprotons

- Institution: CERN
- Department: EP Seminar
- Speaker: Stefan Ulmer
- Year: 2018
- Language: English
- Source: [CERN](https://videos.cern.ch/record/3006041)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Teens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

The Baryon Antibaryon Symmetry Experiment (BASE-CERN) at CERN's antiproton decelerator facility is aiming at high-precision comparisons of the fundamental properties of protons and antiprotons, such as charge-to-mass ratios, magnetic moments and lifetimes. Such experiments provide sensitive tests of the fundamental charge-parity-time invariance in the baryon sector.

BASE was approved in 2013 and has measured since then, utilizing single-particle multi-Penning-trap techniques, the antiproton-to-proton charge-to-mass ratio with a fractional precision of 69 p.p.t. \[1\], as well as the antiproton magnetic moment with fractional precisions of 0.8 p.p.m. and 1.5 p.p.b., respectively \[2\]. At our matter companion experiment BASE-Mainz, we have performed proton magnetic moment measurements with fractional uncertainties of 3.3 p.p.b. \[3\] and 0.3 p.p.b. \[4\]. By combining the data of both experiments we provide a baryon-magnetic-moment based CPT test

gpbar/gp = 1.000 000 000 2(15),

which improves the uncertainty of previous experiments by more than a factor of 3000 \[5\]. A unique antiproton reservoir trap used in BASE, furthermore allows us to set constraints on directly measured antiproton lifetime. Our current value tp>10.2a improves previous best limits by a factor of 30 \[6\].

In this talk I will review the achievements of BASE and will give an outlook on our future physics program.

\[1\] S. Ulmer et al., Nature 524, 196 (2015).

\[2\] C. Smorra et al., Nature 550, 371 (2017).

\[3\] A. Mooser et al., Nature 509, 596 (2017) (2014).

\[4\] G. Schneider et al., Science 358, 1081 (2017).

\[5\] J. DiSciacca et al., Phys. Rev. Lett. 110, 130801 (2013).

\[6\] S. Sellner et al., New. J. Phys. 19, 083023 (2017). .

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## Lectures

1. [Challenging the Standard Model: High-Precision Comparisons of the Fundamental Properties of Protons and Antiprotons](https://invisiblenetwork.ai/learn/cern/3006041/5ae35f37127d), 1 h 6 min (CERN's player)