Physics Studies of Antihydrogen Atoms

Abstract: 

Precision spectroscopy of antihydrogen is a promising path to sensitive tests of CPT symmetry. The ALPHA Collaboration, in series of experiments at the CERN Antiproton Decelerator, has combined antiprotons and positrons to create antihydrogen atoms in a magnetic minimum trap. Trapping times of 1000s have been achieved and recent improvements in antihydrogen synthesis techniques increased trapping rates by an order of magnitude, reaching about 14 trapped antiatoms per trial.  In 2016, two-photon laser excitation with 243 nm light was employed to conduct the first measurements of the 1S-2S transition in neutral antimatter. These initial measurements of the antihydrogen transition frequency indicated that it is equal to its hydrogen counterpart at the level of $\sim 2\times 10^{-10}$.    A technique based on Fermi acceleration was used to set a bound on the charge neutrality of antihydrogen to $\sim < 10^{-9}$ e and microwave experiments have induced positron spin flips. The talk will conclude with our plans for significant improvements in precision measurements and for gravity experiments in the near future.