First Spectroscopy of Antihydrogen with Laser-Cooling assisted Antihydrogen Trapping

Antimatter lies at the heart of one of the most profound mysteries in our current understanding of the universe. Since the discovery of quantum mechanics, the description of the very small, and Einstein's general relativity theory, the description of the very large, the two have been at odds with each other. Quantum mechanics predicts the existence of a mirror image of matter, the so-called antimatter, which was soon confirmed. However, quantum mechanics also predict that the universe should be symmetric with respect to matter and antimatter or in other words that half the universe should be made of antimatter. Until now we have found no evidence of bulk antimatter in the universe a fact that remains a mystery in science. This is where Einstein may perhaps enter the stage. Einstein's theory describes the development of the very large (stars, galaxies, the universe) very well, but it is not compatible with the quantum world. A description of our world capable of encompassing both the very large and the very small has thus far eluded science. Such a description will have to include an explanation for the apparent lack of antimatter in the universe.

The recent start up of the LHC forms part of the effort to address this fundamental problem in our understanding of the world around us. This fellowship forms part of another, low energy, approach to the same issue. We are working towards detailed studies of the structure of neutral atoms made of antimatter. According to quantum mechanics their structure should be exactly the same as their matter counterparts. To accomplish this goal we are trapping Antihydrogen and plan to compare it to Hydrogen. As quantum mechanics predicts that these atoms should have identical internal structure to any level of precision, any difference we may discover will deliver ground-breaking information for our understanding of the universe. The making and trapping of these anti-atoms is a delicate affair, and the work here builds on many years of experience in the production of Antihydrogen and the recent successful trapping of the same. The motivation for making atoms is that these are neutral and can be probed by one of the best precision tools available to science - lasers. Precise measurements on atomic systems have been perfected over the last century and the advent of lasers accelerated the field far beyond other fields of precision measurement, such that today, we can measure transitions in atoms with up to 17 decimal places of precision. We plan to apply the techniques with this unfathomable precision to study our trapped Antihydrogen atoms.

However, this lofty goal requires very precise control over the formation of the Antihydrogen. The Antihydrogen must be trapped to allow for precise measurements of its internal structure. As Antihydrogen is neutral, it cannot be easily trapped. However, we can trap Antihydrogen in a magnetic trap. This is possible as Antihydrogen, though neutral, has a structure, which causes it to have a small magnetic moment, or in other words behave as a very small magnet. The tricky bit to trapping the Antihydrogen is that this dipole moment is so small, that even with state-of-the-art magnetic fields, our trap can only hold atoms so slow that their energy corresponds to a temperature less than half a degree above absolute zero. We are therefore currently only able to trap about one atom at a time. This project aims to facilitate the production of very cold Antihydrogen by using Beryllium ions, which can be cooled using a technique called laser-cooling. These ions can be cooled to a few thousandth of a degree above absolute zero, and can thus be used as a heat sink for the particles used to form Antihydrogen. We expect that this effort could significantly increase the number of trapped atoms and allow us to study the differences between Antihydrogen and Hydrogen in great detail. If any difference is found it will have a profound impact on physics as we know it.

Academic beneficiaries of this work have been discussed previously under the appropriate heading.
In the past as well as in connection with the recent breakthrough our work has achieved impact via the massive media publicity it has received across the scientific and popular press. This has included articles in the national press in many countries, and interviews with radio and television. A recent example is "Scientists trap antimatter long enough to study how it works." (A. Jha, The Guardian, 5/6/11). The proposed work should see further scientific breakthroughs, which will achieve similar publicity. We will continue to engage with the press to promote our work and plan taking communication courses to improve the impact of this. We will also continue to engage through semi-popular articles targeting non- specialists and school students.

The benefits to stakeholders, society and people come in a variety of forms. While fundamental science of the nature proposed here is not targeted towards specific applications or improvements in industry or civilian life, it is crucial to the health of society that we continue to question the nature of the world around us. Asking and answering questions about the natural world is an important part of a modern democratic society as it helps shake people out of complacency and stagnation. Is it also crucial to the continued health of UK industry that we continue to develop home grown knowledge at the forefront of science. Recent focus has been on applied science and the application of science directly to industry, but it is often forgotten that the science needed to get to the knowledge that may then be redirected to target specific societal issues is the fundamental science which is driven purely by the desire to understand the world around us.

In more concrete terms, the massive publicity our research is host to inspires thousands of students to engage through site visits and school presentations both in Swansea and at CERN (which has about 30000 visitors per year). It encourages them to question the world around them and established truths, a critical element in a healthy society, and in particular it inspires them to enter STEM disciplines themselves and become the builders of the future of the UK and the world. We will continue to engage with students and the public through outreach at fairs, site-visits at CERN and Swansea as well as talks targeting the general public and school visits.

Direct benefits come from the output of trained personnel. This benefits both the personnel and the UK who acquire a highly qualified work force in the process. PDRA's and students are given great opportunities to work at the world particle physics flagship CERN and on our world-renowned research. Apart from the concrete science skills earned, the strict requirements imposed by beam-time (such as readiness and just-in-time problem-solving), our experiment employs a large panoply of experimental techniques and physics sub-disciplines, which make our students and PDRA's highly valuable at the end of service. Being at CERN has the side-benefit for the UK students that it gives them international experience highly sought after in an increasingly globalised world.

The PI is engaged in particular in the student aspect of impact through taking the initiative to propose and then organise a winter school on the physics of trapped charged particles and plan to continue such activities in the future.