Towards precise comparisons of Hydrogen and Antihydrogen

Building on decades of world-leading work to facilitate the scrutiny of antihydrogen, the bound state of an antiproton and a positron, we intend to perform precise measurements of the properties of the anti-atom and develop techniques towards comparisons with hydrogen. Investigations of hydrogen, the most abundant atom in the universe, have been instrumental in the development of modern physics. However, its antimatter counterpart, antihydrogen, must be made in the laboratory to be studied as it does not occur naturally. Antihydrogen is purported to be the mirror-image of hydrogen in the sense that, since only the sign of the charge of the constituents is reversed, it should obey the same laws of physics and hence be identical in every way: e.g., the atomic spectral lines should be the same. Additionally, Einstein’s Equivalence Principle states that it should obey the laws of gravity in the same way as any other massive object (e.g., hydrogen). The supposed similarity of matter and antimatter leaves the virtual absence of antimatter in the Universe a conundrum that physics has yet to explain. To hopefully address this problem, as well as elucidate the fundamental symmetry assumptions at its core, we will use the most advanced techniques available, many of which we have developed, to study antihydrogen. We will perform the most precise measurements to date of several lines of its atomic spectrum. The 1S-2S ground to first excited state line features strongly as the best measured line in hydrogen, thus allowing for the most precise comparison. Combining this transition with the measurement of others will allow us to extract some fundamental constants in antihydrogen. These spectroscopic measurements will build on our recent first measurement of the 1S-2S transition in antihydrogen. In a separate endeavour, we will build on our pioneering observation of the effect of gravity on antihydrogen, to do more precise measurements of the gravitational acceleration experienced by antihydrogen. For all this work we will use our unique capacity to synthesise, trap and accumulate thousands of antihydrogen atoms in our magnetic traps. The ultimate goal is the direct comparison with hydrogen using the same experimental techniques in the same place at nearly the same time. Starting from our unique antihydrogen set-up, we will explore methods to make the antihydrogen experiments applicable to hydrogen and develop techniques to magnetically trap hydrogen in our antihydrogen apparatus. Methodologies applicable only to antihydrogen, such as exploiting antihydrogen annihilation on contact with matter, will have to be replaced by techniques applicable also to matter atoms in a matter dominated world. While we are confident that we will succeed in improving measurements on antihydrogen, and eventually compare those with equally precise measurements on hydrogen, we cannot predict if these measurements will show a difference between matter and antimatter. However, if they do, some of the most fundamental tenets of modern physics will have to be revisited, with a profound impact on fundamental science.