Fundamental Symmetry Tests with Trapped Antihydrogen: ALPHA at CERN/AD

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This grant will support Canadian contributions to the scientific program of the CERN-based ALPHA Collaboration. The goal of ALPHA is to measure properties of the antihydrogen atom to the highest precision possible, and to compare them to those of the ordinary hydrogen atom. These comparisons serve as tests of fundamental symmetries between matter and antimatter, and are expected to shed light on issues that rank amongst some of the greatest unsolved problems in physics. The ALPHA Collaboration comprises approximately 50 scientists from 15 institutions in 7 countries. More than a third of those individuals come from Canadian research laboratories and universities (collectively called ALPHA-Canada), and will be supported by this grant. ALPHA-Canada has been funded by NSERC continuously since the ALPHA Collaboration was formed in 2005, and has played leading roles in many of ALPHA's most significant accomplishments. Examples of earlier high-profile milestones driven by NSERC funding include: stable (Nature 2010) and long term (Nature Physics 2011) trapping of neutral antimatter, proof of principle microwave spectroscopy (Nature 2012), and tests of charge neutrality (Nature Communications 2014 and Nature 2016). During the tenure of our most recent three-year funding cycle, we dramatically advanced the field of antihydrogen physics. In particular, construction and commissioning of a new apparatus (ALPHA-2) enabled us to transition from what one might call “proof-of-principle” demonstrations to a robust program of precision physics. Examples of scientific milestones attained since our last SAP Project Grant application was submitted to NSERC (October 2016) include: observation of laser-induced two-photon 1S-2S transitions in antihydrogen (Nature 2017), and a subsequent 2 part-per-trillion measurement of the frequency of that transition (Nature 2018); observation of the ground hyperfine spectrum of antihydrogen (Nature 2017), and a subsequent 9 part-per-million measurement of the frequency of that transition (Nature, under review); observation of the 1S-2P Lyman-alpha transition in antihydrogen (Nature 2018), and a subsequent measurement of the fine structure and Lamb shift (Nature, under review); and laser-cooling of antihydrogen and subsequent 1S-2S spectroscopy of laser-cooled antihydrogen (manuscripts under preparation). Further to this, we have developed and constructed yet another antihydrogen apparatus: ALPHA-g. The purpose of ALPHA-g is to enable experiments that will probe the gravitational interaction between antihydrogen and the Earth, yielding a first direct test of Einstein's Equivalence Principle in the antimatter sector. ALPHA-Canada has, is, and will play leading roles most aspects of the ALPHA-g program. In this application, we request funding to support and exciting and highly visible three-year program of activities that will significantly advance the frontiers of precision fundamental symmetry tests with antihydrogen atoms.