Nikhef colloquium "1S-2S Spectroscopy of Antihydrogen in the ALPHA Experiment" by Chris Rasmussen (Alpha Collaboration)

Friday 18 May 2018, 11:00 → 12:00 Europe/Amsterdam

H331 (Nikhef)

Precision measurements of magnetically trapped antihydrogen provides a unique and powerful way to test matter-antimatter symmetries. A cornerstone of the standard model,
CPT symmetry demands that the spectrum of antihydrogen be identical to that of its
ordinary matter counterpart. Of particular interest is the 1S-2S transition which has been
measured in hydrogen[1] with the remarkable relative precision of a few parts in 10¹⁵, and promises a particularly elegant and high precision test of CPT symmetry by comparis onto antihydrogen.
In 2016, the ALPHA collaboration made the first observation[2] of the 1S-2S transition
in antihydrogen, and very recently this measurement was drastically improved[3] to reach
a fractional precision of  2x 10^-12. The observed frequency in antihydrogen is consistent
with CPT symmetry at the current level of precision.
In this talk, I will present this latest measurement of the 1S-2S transition and introduce
the methods of anti-atom spectroscopy developed by ALPHA. Finally, I will touch on
future improvements needed to take this milestone measurement to the same precision as its hydrogen counterpart.

[1] Parthey, C.G. et al, Phys. rev. lett. 107, 203001 (2011).
[2] Ahmadi, M. et al, Nature 541, 506-510 (2017).
[3] Ahmadi, M et al, Nature (2018)

Slides NIKHEF_Chris_Rasmussen_ALPHA.pdf