Frequency metrology for precision measurements on matter-antimatter symmetry

Lead Research Organisation: Swansea University
Department Name: College of Science


The virtual absence of antimatter and preponderance of matter in the Universe today remains one of the biggest conundrums facing physics. Already in 1967, the famous Sakharov conditions described how this asymmetric Universe could come about by requiring symmetry violations (i.e. differences) between matter and antimatter. Until now, no sufficient symmetry violations have been found to resolve this question, thus the puzzle remains. This project aims to seek answers to this question by directly testing the supposition that the structure of atoms made of antimatter is indistinguishable from the structure in their matter counterparts.

This grant proposes the installation of a caesium fountain atomic clock which will allow spectroscopic measurements of antihydrogen with an uncertainty commensurate with how accurately we can measure time itself. This project provides state-of-the-art equipment for our long-term programme where we use this ultimate tool of precision measurements to address the antimatter conundrum. Our approach is to trap antihydrogen atoms, (atoms that we make by combining antiprotons and positrons) in order to study their internal structure using spectroscopic techniques from atomic physics. We draw from work that have given us the most precise gauges in the scientific toolbox to date and the basis for the global positioning system (GPS); atomic clocks. Specifically, we investigate the ground to first excited state transition in antihydrogen (antimatter) held in a magnetic trap to test the hypothesis that the frequency of this transition is exactly the same as that of hydrogen (matter). This transition has been investigated with a staggering 15 decimal places of precision in hydrogen. We have recently achieved a precision of 12 decimal places in antihydrogen. Improving our antimatter-work to match the result in matter experiments requires us to determine the antihydrogen 1S-2S transition frequency with the accuracy of the corresponding measurement in hydrogen. The new equipment is a state-of-the-art atomic clock identical to the type that makes the definition of the SI-second practical. Since the atomic clock directly measures the hyperfine interval in caesium as defined in the SI-system of units, it will give us the best possible absolute frequency reference and allow us to reach the precision achieved in matter with antimatter.

The antimatter research that this project enables , tests the very foundations of physics that explains the world around us and forms the basis technology of increasing complexity. Despite all this success, we still do not understand why there appears to be no bulk antimatter in the Universe. In this project we look for tiny deviations from expectations based on our current understanding. Experience shows that precise observation of Nature leads to breakthroughs in our understanding. Here, antihydrogen is a compelling subject due to the very specific predictions of its properties, and the already available precise results in its matter counterpart. The risk of finding no new clues on this path is far outweighed by the risk of not looking for them when we now very clearly can. An observed difference between antihydrogen and hydrogen that can be attributed to symmetry breaking would have profound, today even unimaginable, consequences on the foundations of physics. Even if no clues are found now, there is immense intrinsic value in the most precise direct measurement of a property in antihydrogen.

Planned Impact

The impact of our work is mainly on the communities that are beneficiaries and, other than the direct academic impact (see elsewhere), these include the stakeholders, the students and staff participating in the project, those who benefit from the output of trained personnel and the general public. This summary as well as the pathways document highlights the overall impact of the antihydrogen activity that will be supported by the requested equipment.

The institutional and organisational stakeholders are Swansea University, as well as the Universities of Liverpool and Manchester (the other ALPHA members in the UK), the other roughly 14 overseas institutions in ALPHA, CERN, and the EPSRC itself. With respect to the latter, we are honoured to have been selected several times for inclusion in its celebratory documents, most recently the Pioneer 14 publication to mark the EPSRC's 20th anniversary. For many years now we have worked closely with the marketing offices of the respective parties in the coordination of the release of publicity materials concerning our research advances. As a result, we have amassed many hundreds of features in the popular press, in specialist magazines and on television, radio and social media. We believe that this not only raises the profile of our work and promotes science to a wide audience, but is also mission-fulfilling for the participating institutions. This is certainly an activity that will be continued.

Direct benefits include many highly trained personnel. Our postgraduate students are afforded a unique experience: they interact with, and work directly alongside in many instances, top physicists from the range of sub-fields embodied within ALPHA. They are entrusted with significant sub-tasks, for which they are directly accountable to the entire collaboration, and emerge with a full repertoire of marketable skills, including a proficiency in the French language. Many of our students continue on to postdoctoral positions around the globe. Postdoctoral researchers on ALPHA are afforded similar, though higher level, opportunities within the programme and many assume important physics and technical coordination roles within the collaboration. We are proud of our record of researchers moving into successful academic careers, including one of the investigators on this proposal.

Public interest in fundamental science, including antimatter, remains high and we think that our feature in the 2016 Royal Society Summer Science Exhibition contributed to this trend. As noted in the "Pathways to Impact" we have begun a Swansea-based initiative aimed at increasing the number of physics teachers in Welsh schools and colleges that participate in the CERN visitors and teachers programmes. This is already having an effect, with more teachers now beginning to organise student trips to CERN.

Most members of the UK teams in ALPHA are active in outreach, at many levels, from local science societies to national festivals. CERN-based colleagues, including our postgraduate students, are frequent hosts of tours of the AD in which ALPHA, and the original apparatus used in the first creation of cold antihydrogen, feature prominently.


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Description Influenced policy on students at CERN
Geographic Reach National 
Policy Influence Type Implementation circular/rapid advice/letter to e.g. Ministry of Health
Impact Our students benefit enormously from being permanently at CERN. They learn to work in an international environment at the largest physics lab in the world. Additionally they have the opportunity to contribute significantly and be a significant part of world-leading research.
Description Winterschool on Physics with Trapped Charged Particles 2012
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Impact Every 3 years I organise a winterschool for PhD Students on the topic of trapped charged particles. The school hosts about 60 students, mostly from Europe, but with a scattering of people from north and south America as well as Asia. It is highly appreciated by everyone in the field and helps young researchers form a wide network in the field as well as of course learning about the field from internationally renowned researchers who join as speakers and tutors. We have done schools in January 2012,2015, 2018 and 2021. I've linked the most recent one below. The next one is planned for January 2024.
Description Precision Experiments with Antihydrogen
Amount £3,512,405 (GBP)
Funding ID EP/V00137X/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 02/2021 
End 06/2025
Description Royal Society Leverhulme Trust Senior Research Fellow
Amount £50,695 (GBP)
Funding ID SRF\R1\201066 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2021 
End 01/2022
Description ALPHA 
Organisation European Organization for Nuclear Research (CERN)
Department ALPHA Experiment
Country Switzerland 
Sector Public 
PI Contribution We have provided 20 years of leadership to antihydrogen research. We have provided expertise in positrons and positron accumulation, trap physics, atomic physics, laser physics, laser-cooling, plasma physics, cryogenics and vacuum technologies.
Collaborator Contribution Partners have provided funding and manpower and expertise in plasma physics, detector physics, analysis, laser physics, particles physics, atomic physics and physics simulation.
Impact Essentially all my outputs in the last 15 years are due to work with ALPHA. ALPHA is multi-disciplinary by nature, as we have to bring together very diverse fields of physics to do research on antihydrogen. The fields covered are accelerator physics, atomic physics, laser physics, detector physics, particle physics, plasma physics, fundamental physics as well as vacuum technology, detector technology, cryogenics and super-conducting magnet technology to mention the most prominent ones.
Description Antimatter at CERN 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Webinar on Antihydrogen in order to engage A-level student locked down due to Covid-19.
Year(s) Of Engagement Activity 2020
Description School visits to Antimatter Factory with tours and presentaitons 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact We engage with school classes coming to CERN to visit the Antimatter Factory though presentations and tours of the facilities. This is a good opportunity for them to add some spice to their education and they often ask pertinent questions and express much appreciation for in particular the antimatter part of the programme.
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019,2020,2022,2023