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

<!--HTML--><p>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.</p> <p>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</p> <p>gpbar/gp = 1.000 000 000 2(15),</p> <p>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&gt;10.2a improves previous best limits by a factor of 30 [6].&nbsp;</p> <p>In this talk I will review the achievements of BASE and will give an outlook on our future physics program.</p> <p>&nbsp;</p> <p>[1] S. Ulmer <em>et al.</em>, Nature <strong>524</strong>, 196 (2015).<br /> [2] C. Smorra <em>et al.</em>, Nature <strong>550</strong>, 371 (2017).<br /> [3] A. Mooser <em>et al., </em>Nature <strong>509</strong>, 596 (2017) (2014).<br /> [4] G. Schneider <em>et al.</em>, Science <strong>358</strong>, 1081 (2017).<br /> [5] J. DiSciacca <em>et al.</em>, Phys. Rev. Lett. <strong>110</strong>, 130801 (2013).<br /> [6] S. Sellner <em>et al.</em>, New. J. Phys. <strong>19</strong>, 083023 (2017).</p>