Forming cold antihydrogen for tests of CPT and WEP
Abstract
The study of CPT invariance with the highest achievable precision in all particle sectors is of fundamental importance for physics. Equally important is the question of the gravitational acceleration of antimatter. In the last decade, impressive progress has been achieved at the Low Energy Antiproton Ring (LEAR) and later at the Antiproton Decelerator (AD) at CERN in capturing antiprotons in specially designed Penning traps, in cooling them to energies of a few milli-electron volts, and storing them for hours in a small volume of space. Positrons have been accumulated in large numbers in similar traps, and low energy positron or positronium beams have been generated. Finally, steady progress has been made in trapping and cooling neutral atoms. Thus the ingredients to form antihydrogen at rest are at hand. Once antihydrogen atoms have been formed, they can be captured in magnetic gradient traps and standard spectroscopic methods can be applied to interrogate their atomic structure with extremely high precision for comparison with the hydrogen atom. Especially, the 1S-2S transition, with a lifetime of the excited state of 122 msec and thereby a natural linewidth of 5 parts in 10^16, offers in principle the possibility to directly compare matter and antimatter properties at a level of 1 part in 10^18. Other quantities of interest, such as the hyperfine structure splitting of the ground state, will also be discussed, as will the possibilities to study gravitational effects on matter and antimatter using ultra-cold antihydrogen. I will describe the techniques used in the ATHENA experiment to decelerate, and accumulate antiprotons at low energy, how to generate high density plasmas of low energy positrons, and how to combine these two species into antihydrogen. The current status of the experiment will be described and an outlook to the immediate future will be given.
- Publication:
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APS April Meeting Abstracts
- Pub Date:
- April 2002
- Bibcode:
- 2002APS..APR.U4003H