Speaker
Description
Antihydrogen, as the simplest purely antimatter atomic system, is a natural candidate for testing fundamental symmetries between matter and antimatter. For example, CPT symmetry predicts that the spectra of hydrogen and antihydrogen should be identical. By making precise measurements of antihydrogen’s transition frequencies, and making comparisons to high precision measurements in hydrogen, we have an excellent test of CPT symmetry in the atomic sector. The primary transitions of interest are the 1S – 2S and ground-state hyperfine transitions, which are known to 4.2 parts in $10^{15}$ and 7 parts in $10^{13}$ in hydrogen, respectively. In addition, the fact that antihydrogen is electrically neutral means it can be used as a probe of the gravitational interaction between matter and antimatter. If the weak equivalence principle holds then the gravitational mass of antimatter should be identical to that of matter but so far there have been no direct free-fall style experiments to test this.
The ALPHA collaboration at CERN aims to test these principles using antihydrogen atoms confined in a magnetic trap. The ALPHA experiment has developed antihydrogen trapping techniques that allow the simultaneous confinement of more than 1000 antihydrogen atoms. This has led to detailed measurements of antihydrogen’s 1S – 2S, 1S – 2P, and ground-state hyperfine transitions. In addition, ALPHA has recently built a new vertical antihydrogen trapping apparatus for a direct measurement of the gravitational free-fall of antihydrogen.
In this talk, I will present a general overview of ALPHA’s apparatus, techniques, and results. Particular focus will be placed on ground-state hyperfine spectroscopy and magnetometry for precision spectroscopy and gravity measurements on trapped antihydrogen.
