Antihydrogen Physics

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

Abstract

Antihydrogen, the bound state of a positron and an antiproton, has recently been created under controlled conditions in the laboratory. The proposal seeks to exploit this advance by facilitating a new generation of experiments on antihydrogen held in a neutral trap, a so-called magnetic gradient trap. This is an arrangement of magnetic fields that acts upon the small magnetic moment of the anti-atom to produce a trapping force. However, such traps are shallow, and are currently only capable of holding antihydrogen in its ground state with kinetic energies equivalent to a temperature below 1 Kelvin. Thus, we need form antihydrogen with these low kinetic energies, a task not yet achieved. Once trapped, we hope to be able to do experiments to manipulate the antihydrogen, using electric and laser fields. Further into the future we hope to be able to produce very cold antihydrogen to make it possible to measure the gravitational interaction of antimatter. However, all experiments with antihydrogen are difficult, so the question we address here is; why bother? We will explain this using the example of symmetry.It has been apparent for a while that fundamental asymmetries are hidden deep within nature. For example, in the 1950's it was discovered that the weak nuclear interaction violates parity conservation. However, the defective parity mirror can be mostly repaired by adding so-called charge conjugation, which, loosely speaking, means that interactions are unaffected when every particle is substituted by its antiparticle. For a while it was believed that the laws of nature would obey the combination of parity reversal and charge conjugation. But by the mid-1960's this was found to be untrue for a small class of reactions involving unusual, fleeting, particles called K-mesons. Since then it has been assumed that the small blemish in the combined charge conjugation/parity reversal mirror can be corrected by the application of time-reversal.However, this 3-way switch differs from the three discrete symmetries, or any 2-way combination of them because the charge/parity/time combination exists as a theorem that can be proved using the basic postulates of quantum field theory. Such theories are the cornerstone of our current understanding of the Universe, but are widely recognised as being incomplete. So testing this unique 3-way switch is going to the heart of our understanding of nature. Our current picture of the beginning of the Universe involves the Big Bang, which is thought to have been an energetic event that created equal amounts of matter and antimatter. Why then did they not all annihilate one another and leave a Universe devoid of matter? Searches for large amounts of remnant antimatter in the Universe have, thus far, failed to find any trace. Currently it is thought that our Universe is matter dominant; in other words asymmetric. The other fact to add to this is that the amount of asymmetry we can currently identify via numerous studies of fleeting and rare particles isn't enough to explain the existence of the material Universe.Thus, it is only by probing the most basic symmetries that we can begin to understand how the Universe we observe came to be.

Publications

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Ahmadi M (2017) Antihydrogen accumulation for fundamental symmetry tests. in Nature communications

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Ahmadi M (2018) Enhanced Control and Reproducibility of Non-Neutral Plasmas. in Physical review letters

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ALPHA Collaboration (2009) Antiproton, positron, and electron imaging with a microchannel plate/phosphor detector. in The Review of scientific instruments

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Amole C (2014) The ALPHA antihydrogen trapping apparatus in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

 
Description In the last year we have been able to observe the 1S-2S transition of antihydrogen and to observe the hyperfine spectrum of the anti-atom.
Exploitation Route The findings obtained during the grant were essential to make progress towards the final goal of testing CPT conservation by comparing the 1S-2S transition of antihydrogen with that of hydrogen.
Sectors Other

 
Description Our findings have been used by many scientists to justify theoretical and experimental work in number of areas of basic physics. Organisations such as CERN and our institutions have used our work to promote their respective missions, and in the public understanding of science.
First Year Of Impact 2011
Sector Other
Impact Types Cultural

 
Description ALPHA Collaboration 
Organisation European Organization for Nuclear Research (CERN)
Department ALPHA Experiment
Country Switzerland 
Sector Public 
PI Contribution As co-founders of the collaboration, we have provided funding and expertise in multiple areas of key importance to this experiment : Super conducting magnets, Lasers, Plasma physics, Trap physics, Antiproton physics, Antitrapping, Positrons, Positron accumulation, Cryogenics.
Collaborator Contribution Partners and expertise (in parenthesis) are come from Brazil (Lasers), Canada (Detectors/DAQ), Denmark (Lasers, Antihydrogen), UK (Detectors, Plasma physics plus the above), US (plasma physics, Simulation). The contributations are estimated based on 10 year running of the experiment with 30 academics contributing cash for running and maintenance and about 20 FTE's per year of running plus 3M of contributions of kit.
Impact This is an enormously successful collaboration having resulted in 4 Nature papers and a large volume of other papers as well as heavy representation in the media. It is physics-multidisciplinary in that the collaboration spans several normally separate areas of physics : cryogenics, plasma physics, atomic physics, particle physics, fundamental physics, laser physics, positron physics, and spectroscopy
Start Year 2006
 
Description CERN 
Organisation European Organization for Nuclear Research (CERN)
Country Switzerland 
Sector Public 
Start Year 2006
 
Description CERN Open Weekend: 2 talks about Antimatter 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact A large number of question after the talks

I don't know
Year(s) Of Engagement Activity 2013
 
Description Royal society summer exhibition 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Exhibition about physics at CERN
Year(s) Of Engagement Activity 2016
 
Description Times Cheltenham Science Festival: Particle Physics: An Introduction" co-presented with Dr Tom Whyntie 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact A number of questions after the talk were answered

None
Year(s) Of Engagement Activity 2013
URL http://www.cheltenhamfestivals.com/science/whats-on/2013/particle-physics-an-introduction/