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Antiproton physics in the ELENA Era
Theo Murphy international scientific meeting organised by Professor Niels Madsen, Professor Michael Charlton, Professor Jeffrey S. Hangst and Professor Walter Oelert.
The CERN Antiproton Decelerator supplies antiprotons to a lively scientific programme. The imminent addition of the ELENA machine will massively increase both the availability and the number of low energy antiprotons. The meeting gathers experts from all across antiproton science to discuss their vision of the new opportunities presented by this step change and how they will profit from and exploit them.
Recorded audio of the presentations will be available on this page after the meeting has taken place. Meeting papers will be published in a future issue of Philosophical Transactions of the Royal Society A.
Attending this event
This is a residential conference, which allows for increased discussion and networking
- Free to attend
- Advanced registration essential (please request an invite)
- Catering and accommodation available to purchase during registration
Enquiries: contact the Scientific Programmes team
Organisers
Schedule
Chair
Professor Michael Charlton, Swansea University, UK
Professor Michael Charlton, Swansea University, UK
Mike Charlton was born in the North East of England and went to Ferryhill School. He studied physics at University College London (UCL) completing his PhD there on the interactions of low energy positrons in gases in 1980. He won a Science and Engineering Research Council Postdoctoral Fellowship in 1982 followed by a Royal Society University Research Fellowship (URF) in 1983, before becoming a Reader in Physics at UCL in 1991.
In 1999 he moved to Swansea University to a Chair in Experimental Physics, where he has also held positions as head of the Department of Physics and of the School of Physical Sciences. He held an Engineering and Physical Sciences Research Council Senior Research Fellowship from 2007-12.
He is a Fellow of the Institute of Physics and is an Inaugural Fellow of the Learned Society of Wales, of which he is also currently a member of the Council. He is a co-recipient of the 2011 American Physical Society James Dawson Award for Excellence in Plasma Physics Research.
He has published over 200 research articles and a monograph and has made many contributions to low energy positron and physics, and in particular connected with antihydrogen research, an initiative he began during his URF.
| 09:15 - 09:45 |
Gravity and antimatter: theoretical aspects
Dr Blas will review the physical case of studying the gravitational properties of antimatter from a theoretical perspective. His plan is to first use an effective description to understand where one can get information about how antimatter gravitates from different phenomena. Second, he will describe which difficulties are faced in the construction of theories consistent these bounds 
Dr Diego Blas, CERN, Switzerland
Dr Diego Blas, CERN, SwitzerlandDiego Blas is a theoretical physicist working at CERN, Geneva. He obtained his PhD from University of Barcelona in 2008 and worked in EPFL, NYU and CERN as a researcher. He is an expert on gravitation and theoretical cosmology. His main interests in gravitation are proposals that try to address the main difficulties of general relativity, namely those related to quantum gravity, black hole physics and dark energy. His proposal for a renormalizable theory of quantum gravity with a preferred frame is currently one of the few viable alternatives to string theory in this endeavour. In cosmology, he is developing new analytical tools to understand the formation of structure at large scales in dark matter scenarios. He is interested in the problem of gravitation and extra forces in antimatter and possible ways to test it in the Universe, the ‘poor’s men accelerator’ in words of Zel’dovich. He is a member of Spanish Society of Relativity and FQXi foundation. |
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| 09:45 - 10:00 | Discussion | |
| 10:30 - 11:00 |
Antiatomic physics
Professor Jonsell will give an overview over what we know about antiproton and antihydrogen scattering on ordinary atoms and molecules. For antiproton scattering, most emphasis will be on inelastic processes, e.g. ionisation and antiproton capture. At the highest energies covered (~100 keV), ionisation is well described by the Born approximation. At lower energies (~10 keV), theoretical descriptions are usually based on classical trajectories in some form. Good agreement with experimental data from the ASACUSA collaboration has been obtained down to 2 keV. Below this limit very little is known from experiments, and we therefore compare classical trajectory calculations, to more advanced quantum mechanical or semi-classical calculations, where available. For collisions involving antihydrogen Professor Jonsell will cover both inelastic processes, which may destroy antiatoms, and elastic collisions, which may eject them from a magnetic trap. At ultracold energies several quantum calculations have been performed for H and He targets. At higher energies, semi-classical approaches have been used. 
Dr Svante Jonsell, Stockholm University, Sweden
Dr Svante Jonsell, Stockholm University, SwedenSvante Jonsell is a senior lecturer in Theoretical Atomic Physics at Stockholm University, Sweden. He is currently a member of the ALPHA and GBAR antihydrogen collaborations at CERN. He got his M.Sc. in Physics at Uppsala University, Sweden, in 1994, where he also continued to do a PhD in Quantum Chemistry, which was completed in 2000. After that he went on a 2-year postdoc as a Nordic Fellow at the Nordic Institute for Theoretical Physics (NORDITA) in Copenhagen. In 2002, he moved to Umeå University in Sweden for a 4-year junior research fellowship, funded by the Swedish Research Council (VR). During this time, he also qualified as a “Docent” in Atomic and Molecular Physics (2004). He was awarded an EPSRC Advanced Fellowship in 2006, when he moved to Swansea University, where he was employed as a lecturer and then senior lecturer. In 2009, he received a Special Research Fellowship from the Swedish Research Council, which took him back to Sweden and Stockholm University. Jonsell has worked on a wide range of topics in theoretical atomic physics, with special emphasis on low-energy scattering problems, in particular involving antiparticles and antiatoms, using both semi-classical and quantum methods. He also works on Monte Carlo simulations of antihydrogen formation. Other research interests include ultracold few-body systems, exotic atoms, and laser cooling. |
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| 11:00 - 11:15 | Discussion | |
| 11:15 - 11:45 |
Prospects of ELENA for testing Lorentz and CPT symmetry with antiprotons
The notion that small deviations from Lorentz symmetry might arise from quantum gravity candidate theories has motivated a world-wide systematic search for Lorentz violation. The Standard-Model Extension (SME) is an effective field theory that facilitates the systematic search for Lorentz violation. The SME contains the standard model of particle physics, general relativity, and all the field operators that break Lorentz and CPT symmetry. Because of the deep connection between CPT symmetry and Lorenz symmetry the SME can also facilitate the systematic test of CPT symmetry. Examples of test models derived from the SME can be found in the literature for antimatter experiments such as antihydrogen spectroscopy experiments, antiproton Penning-trap experiments, and antimatter gravity tests. The SME coefficients quantify any deviation from Lorentz and CPT symmetry, and for that reason the sensitivity of the experiments to the coefficients indicate the value of the experiments as probes of Lorentz and CPT symmetry. The addition of ELENA to the Antiproton Decelerator at CERN will allow experiments to increase the sensitivity to coefficients for CPT and Lorentz violation, improving the limits at which these symmetries have been tested or perhaps discovering violations of them in nature. 
Dr Arnaldo Vargas, Loyola University New Orleans, USA
Dr Arnaldo Vargas, Loyola University New Orleans, USADr. Vargas is a theoretical physicist who is a Visiting Assistant Professor at Loyola University New Orleans. He obtained his undergraduate degree in science from the University of Puerto Rico and his Ph.D. from Indiana University. His current research interests include the systematic tests of fundamental principles of physics. Notably, in recent years Arnaldo has been studying the prospects of using spectroscopy experiments for testing CPT and Lorentz symmetry. His publications have considered the feasibility of testing the aforementioned symmetries in spectroscopy experiments with conventional matter such as hydrogen, deuterium, and hydrogen molecules. He has also investigated the possibilities of searching for CPT and Lorentz violation in spectroscopy experiments with exotic matter such as antihydrogen, muonium, positronium, muonic hydrogen, muonic deuterium, and other muonic ions. In conjunction with his collaborators, Arnaldo has identified signals for deviations from Lorentz and CPT symmetry accessible to spectroscopy experiments such as sidereal variation and annual variation of transition frequencies, and discrepancies between the spectrum of hydrogen and antihydrogen. Another result showed in his publications is that Lorentz violation can allow for discrepancies between hydrogen, deuterium, and muonic-hydrogen spectroscopy experiments. |
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| 11:45 - 12:30 | Discussion |
Chair
Professor Niels Madsen, Swansea University
Professor Niels Madsen, Swansea University
Professor Madsen is co-founder and deputy spokesperson in the ALPHA collaboration that is a world leading antihydrogen group. ALPHA was the first group to trap antihydrogen, first to observe quantum transitions and first in observing the 1S-2S two photon optical transition. He has been actively involved in antihydrogen research since 2001, playing a substantial role in the ATHENA team that first formed low energy antihydrogen in 2002. As a Professor at Swansea University he has a research group at CERN. His group plays a leading role in the ALPHA experiment in both physics and hardware and software design, and led efforts to implement several key techniques leading to the first antihydrogen trapping and first microwave and optical transitions. It has furthermore conceptualised, designed and built significant parts of the ALPHA apparatus. For this work he has been awarded a Royal Society Senior Leverhulme Fellowship in 2010, and the 2011 James Dawson Award for Excellence in Plasma Physics Research. In collaboration with ALPHA he is pursuing precision studies of antihydrogen in all areas possible, including gravitation, and is looking forward to exploit the ELENA upgrade to the CERN antimatter facility that will greatly enhance the availability of low energy antiprotons. He is furthermore active in engaging with schools, teachers and the general public in all that concerns antimatter at CERN and was co-organiser of the successful Antimatter Matters exhibition at the Royal Society Summer Exhibition in 2016.
| 13:30 - 14:00 |
Precision measurements of trapped antihydrogen in the ALPHA experiment at CERN
Precision measurements of trapped antihydrogen in the ALPHA experiment at CERN Antihydrogen, the antimatter equivalent of hydrogen, offers a unique way to test matter-antimatter symmetry. In particular, the CPT (charge, parity and time) theorem requires that hydrogen and antihydrogen have the same spectrum. Antihydrogen can reproducibly be synthesised and trapped in the laboratory for extended periods of time, offering an opportunity to study the properties of antimatter in detail. New techniques to study antihydrogen have emerged; the ALPHA collaboration at CERN can now interrogate the ground state energy structure with resonant microwaves, determine the gravitational mass to inertial mass ratio and measure charge neutrality. Very recently, the collaboration has observed the 1S-2S transition in trapped antihydrogen; the first observation of resonant interaction of light with an anti-atom. Due to the narrow intrinsic linewidth of the transition and use of two-photon laser excitation, the transition energy can be precisely determined in both hydrogen and antihydrogen, allowing a direct comparison. Our result is consistent with CPT invariance at a relative precision of around 2×10-10. This constitutes the most precise measurement of a property of antihydrogen. Here, I present the most recent work of the collaboration on antihydrogen in the ALPHA-2 apparatus and an outlook on improving the precision of measurements involving lasers and microwave radiation. 
Dr Stefan Eriksson, Swansea University, UK
Dr Stefan Eriksson, Swansea University, UKStefan Eriksson is a physicist who has conducted pioneering research on both matter and antimatter at temperatures approaching absolute zero. He is known for his contribution to antihydrogen research, in particular the first resonant excitation of the two-photon transition to the first excited state of antihydrogen with the ALPHA collaboration at CERN. He has also developed new techniques to study cold matter with components small enough to create chip-scale devices. His research is currently focused on precision tests of the fundamental symmetries of Nature, and developing new ways to use nanoscale optics in experiments with ultracold atoms. Stefan is currently Reader in Physics at Swansea University. He received is PhD from the University of Helsinki after which he spent an extensive period at Imperial College, London before taking up his current post. He held a Leverhulme Research Fellowship 2014-2016. |
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| 14:00 - 14:15 | Discussion | |
| 14:15 - 14:45 |
ATRAP
Professor Gerald Gabrielse, Harvard University, USA
Professor Gerald Gabrielse, Harvard University, USAGerald Gabrielse is the Leverett Professor of Physics at Harvard and a member of the NAS. His ideas and demonstrations launched and guide the low energy antiproton and antihydrogen physics being pursued by hundreds at a storage ring built for this purpose. His demonstration (with the TRAP collaboration he led) that the antiproton and proton have charge-to-mass ratios that are opposite to 9 parts in 1011 is the most stringent baryon test of the CPT symmetry that is intrinsic to the standard model of particle physics. His proposal to form and trap cold antihydrogen has been realize by the ATRAP team he leads and others. The electron magnetic moment that he measured to 3 parts in 1013 is the most precisely measured property of an elementary particle. This made possible the most precise confrontation of theory and experiment, with his measurement confirming what is the standard model's most precise prediction. His electron electric dipole measurement advanced the state of the art by a factor of 12, constraining proposed extensions to the standard model at the TeV energy scales being investigated at the LHC. Gabrielse chaired the Harvard Physics Department and the DAMOP division of the APS. His many awards include both Harvard’s Levenson prize for exceptional teaching and its Ledlie prize for exceptional research. The APS awarded him both its Davvison-Germer Prize and its Lilienfeld Prize. Germany awarded the Humboldt Research Award and Italy the Tomassoni and Chisesi Prize. He is widely sought after for lectures on his physics research, for science lectures to high school students, teachers and the general public, and for lectures on science and religion. For the latter he received the Trotter Prize. |
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| 14:45 - 15:00 | Discussion | |
| 15:30 - 16:00 |
History and prospects for antihydrogen gravitation measurements
The ALPHA experiment at CERN is focused on performing precision measurements on low energy antihydrogen in an effort to rigorously test symmetries between matter and antimatter underlying many theories in contemporary physics. With the recent observation of the 1S-2S transition in a population of trapped antihydrogen atoms, ALPHA has entered the era on performing high precision atomic physics measurements on this trapped atom. ALPHA-g is a new experiment designed to perform direct free-fall measurements of antihydrogen in Earth’s gravitational field. The goal is to improve on the proof-of-principle experiment conducted in, with the ultimate goal of achieving a 1% measurement on antimatter gravitational acceleration g. This talk will present background on the proposed experiment as well as the current status of the project. 
Dr. William Bertsche, University of Manchester, UK
Dr. William Bertsche, University of Manchester, UKDr. William Bertsche is presently a Lecturer in the School of Physics and Astronomy at the University of Manchester and a member of the Cockcroft Institute of Accelerator Science. He developed a background in fundamental plasma physics with a focus on the dynamics of single-charge plasmas confined in trap, earning his PhD in 2007 from the University of California, Berkeley. In 2005, he joined the newly-formed ALPHA Collaboration as a student to address the underlying plasma challenges related to the production and trapping of cold antihydrogen atoms. He continued with the collaboration after earning his degree and ultimately participated in the first experiments to directly manipulate the internal states of any neutral antimatter system. In 2012, Dr. Bertsche was appointed as Lecturer and the University of Manchester. He was subsequently elected as the Technical Coordinator for the ALPHA Collaboration, and oversaw the design, commissioning and operation of ALPHA-2, the apparatus that performed the first optical spectroscopic interrogation of antihydrogen. In 2017, he was appointed as a Deputy Spokesperson for ALPHA-g, the next generation atom trap at ALPHA with the goal of performing direct measurements of antimatter gravitation. |
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| 16:00 - 16:15 | Discussion | |
| 16:15 - 17:00 | Poster session |
Chair
Professor Jeffrey S. Hangst, Aarhus University
Professor Jeffrey S. Hangst, Aarhus University
Jeffrey S. Hangst is a graduate of MIT (SB, SM) and of the University of Chicago (PhD). He worked at Fermilab and at Argonne while doing his PhD at Chicago. He moved to Aarhus University in Denmark in 1994 and has been there since. Hangst received the European Physical Society's 1996 accelerator award for a young scientist for his work on laser cooling of stored ion beams in the ASTRID storage ring in Aarhus. He has been stationed at CERN full-time since 2001. He is a founding member of the ATHENA antihydrogen collaboration and was the Physics Coordinator of the experiment that produced the first cold antihydrogen atoms at the CERN Antiproton Decelerator (AD) in 2002. This breakthrough was featured on the cover of the New York Times. He is the founder and Spokesperson of the ALPHA collaboration, which demonstrated trapping of antihydrogen atoms in 2010, and the first laser spectroscopy of antihydrogen in 2016. ALPHA’s trapping of antihydrogen was voted ‘Physics Breakthrough of the Year’ by Physics World magazine in 2010. Hangst was elected to fellowship of the American Physical Society, Division of Plasma Physics, in 2005. He received the John Dawson award for excellence in plasma physics from the APS in 2011, and the Ångstrom medal from Uppsala University in 2013 for his work on trapped antihydrogen. He currently holds an elite Advanced Grant (2013-2018) from the European Research Council, and in 2016, he was awarded a prestigious Semper Ardens grant from the Carlsberg Foundation to pursue work on gravitational studies of antimatter.
| 09:00 - 09:30 |
Challenging the Standard Model by the precise comparisons of the fundamental properties of protons and antiprotons.
The Standard Model (SM) of particle physics is known to be incomplete. This inspires various searches for physics beyond, among them are tests of charge, parity, time (CPT) invariance that compare the fundamental properties of matter/antimatter conjugates at low energy and with high precision. The Japanese/German BASE collaboration at the antiproton decelerator of CERN targets high-precision comparisons of the fundamental properties of antiprotons and protons, namely, charge-to-mass ratios and magnetic moments. To perform these tests we have developed an advanced Penning trap spectrometer which enabled the most precise measurement of the proton magnetic moment with a fractional precision of 3.3 parts in a billion, the most precise comparison of the proton-to-antiproton charge-to-mass ratio, with a fractional precision of 69 parts in a trillion, as well as the most precise measurement of the magnetic moment of the antiproton (0.8 p.p.m). Recent improvements in the stability of the apparatus enabled us to observe single antiproton spin transitions, based on this achievement a 100-fold improved measurement of the antiproton magnetic moment will become possible. This talk will summarise our most recent results and give an overview on the perspectives of BASE in the ELENA era. 
Dr Stefan Ulmer, RIKEN, Japan
Dr Stefan Ulmer, RIKEN, JapanStefan Ulmer is a chief scientist at RIKEN, Japan, founder and spokesperson of CERN’s BASE collaboration. He has received his PhD degree for the “first observation of spin flips with a single trapped proton”, which was a milestone experiment in proton/antiproton magnetic moment measurements. Following his work the BASE collaboration performed the most precise measurement of the magnetic moment of the proton with a fractional precision of 3 parts in a billion. In 2012 he joined the ASACUSA antihydrogen effort as a post-doc where he contributed to the production of the first beam of antihydrogen atoms, setting up the BASE experiment in parallel. In the first run of the BASE experiment (2014) he and his team performed the most precise test of CPT invariance with baryons by comparing the proton-to-antiproton charge-to-mass ratio with a fractional precision of 69 parts in a trillion. He invented a reservoir trap technique which enables BASE to operate antiproton experiments independent of accelerator cycles, and demonstrated in 2016 trapping of antiprotons for more than 405 days. In 2017 BASE reported on the most precise measurement of the magnetic moment of the antiproton with a fractional precision of 0.8 parts in a million. Very recently, BASE published a paper on the first observation of single antiproton spin transitions, which is a major step towards a measurement of the antiproton magnetic moment with a fractional precision on the parts-per-billion level. For his work on high-precision comparisons of the fundamental properties of protons and antiprotons he received the IUPAP young scientist award 2014. |
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| 09:30 - 09:45 | Discussion | |
| 10:15 - 10:45 |
GBAR: leading the dance with ELENA's antiprotons
In order to observe the free fall of antihydrogen atoms, hence measuring the gravitational acceleration of antimatter on Earth, the GBAR experiment aims at producing these antiatoms with velocity of a few m.s-1. This will be achieved by implementing the sympathetic cooling of antihydrogen positive ions, an original idea proposed by J. Walz & T. Hänsch. As ELENA’s first user, GBAR is currently getting ready to receive the first 100 keV antiprotons. The present status of the installation in the AD hall and the planning of the coming years are then detailed. The recording of GBAR’s first antihydrogen free falls will provide a 1% precision on the measurement of g ̅; in order to further improve this precision to 0.01%, a future upgrade of the experiment is already being studied. Finally, it is worth noting that each antiproton bunch delivered by ELENA to GBAR also bears the potentiality of a few hundreds of antihydrogen atoms, while a large part of the antiprotons remains untouched. Ideas proposed to exploit these beams are also sketched. 
Dr Pauline Comini, ETH Zürich, Switzerland
Dr Pauline Comini, ETH Zürich, SwitzerlandPauline Comini obtained her PhD from the Université Pierre et Marie Curie in 2014 on the production of antihydrogen atoms and ions in the GBAR experiment. For this study, she worked with three institutes for the collaboration: the CEA-Saclay, hosting the project, the Institut de Physique et de Chimie des Matériaux from Strasbourg (IPCMS), for the cross section calculations of the atomic processes involved in GBAR, and the Laboratoire Kastler-Brossel (LKB) in Paris, for the assembly of a laser dedicated to positronium excitation. Her doctoral thesis was awarded the 2014 Daniel Guinier price for young physicists by the French Physical Society, and the theoretical part, published in 2013 in New Journal of Physics, was selected in the "Highlights of the year" by the journal. In 2015, as a postdoc at ETH Zurich, she worked on the direct two-photon excitation of positronium to Rydberg states, in preparation for subsequent Stark deceleration. Since 2016, she is a permanent physicist in the GBAR group at CEA-Saclay, focusing on the optimisation of the reaction chamber for the antiproton-positronium interaction. |
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| 10:45 - 11:00 | Discussion | |
| 11:00 - 11:30 |
The ELENA facility
The CERN Antiproton Decelerator AD provides antiproton beams with a kinetic energy of 5.3 MeV to an active users community. This extraction energy is the lowest one possible under good conditions with the given circumference of the AD. 
Dr Christian Carli, CERN, Switzerland
Dr Christian Carli, CERN, SwitzerlandChristian Carli is working as accelerator physicist at CERN. He has contributed to the I-LHC project to upgrade the CERN ion accelerator chain to provide lead ion beams for the LHC and, in particular, led the commissioning of the Low Energy Ion Ring LEIR, the exploitation and improvements of the PS Booster and commissioning of the Antiproton Decelerator AD. He has contributed to the I-LHC project to upgrade the CERN ion accelerator chain to provide lead ion beams for the LHC and, in particular, led the commissioning of the Low Energy Ion Ring LEIR. Furthermore, he has contributed to the exploitation and improvements of the PS Booster and the commissioning of the Antiproton Decelerator AD. |
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| 11:30 - 12:15 | Discussion |
Chair
Professor Walter Oelert, Johannes Gutenberg University, Germany
Professor Walter Oelert, Johannes Gutenberg University, Germany
Walter Oelert is retired from the position as a scientific co-worker at the Research Centre Jülich and as Professor from the Ruhr University Bochum both located in Germany. He still works as a Visiting Scientist at the Research Centre CERN/Genève/Switzerland and as a Supervisory Professor at the Johannes Gutenberg University Mainz/Germany. After starting his career in Nuclear Physics by investigating few nucleon transfer reactions, his work concentrated in the production of baryons and mesons with strangeness at the COSY accelerator in Jülich, the Celsius ring in Uppsala as well as the LEAR facility at CERN.
In 1995 his team observed the first ever seen anti-hydrogen atoms. Presently he is involved in the construction of the ELENA ring at CERN, a facility which decelerates the antiproton down to 100 keV, which will increase the experimental efficiency by orders of magnitude.
| 13:15 - 13:45 |
Determination of the antiproton-to-electron mass ratio by laser spectroscopy of antiprotonic helium atoms
The (anti)proton-to-electron mass ratio is a fundamental dimensionless constant of nature that serves as a basis of our international system of units. The Atomic Spectroscopy and Collisions Using Slow Antiprotons (ASACUSA) collaboration at CERN is carrying out precise laser spectroscopy experiments of antiprotonic helium. This is a three-body atom composed of a normal helium nucleus, an electron, and an antiproton occupying a highly excited Rydberg state. Various techniques such as sub-Doppler two-photon laser spectroscopy and buffer gas cooling of the atoms to cryogenic temperature T=1.5-1.7 K are employed to measure their transition frequencies to a precision of 2.5 parts in a billion. By comparing the results with three-body quantum electrodynamics calculations, the antiproton-to-electron mass ratio was determined as 1836.1526734(15). This agreed with the known proton-to-electron mass ratio at a precision of 0.8 parts per billion. This constitutes a consistency test of CPT symmetry. 
Dr Masaki Hori, Max Planck Institute of Quantum Optics, Germany
Dr Masaki Hori, Max Planck Institute of Quantum Optics, GermanyBorn in Tokyo, Japan. Research interests: Particle, nuclear, and atomic physics, lasers. Work experience: PhD, University of Tokyo (2000), CERN fellow (2002-), Group leader, Max-Planck Institute for Quantum Optics (2008-). Inoue Prize for Young Scientists (2002), European Young Investigator’s Award (2007), European Research Council Starting Grant (2012). |
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| 13:45 - 14:00 | Discussion | |
| 14:00 - 14:30 |
AEgIS at ELENA: outlook for physics with a pulsed cold antihydrogen beam
The efficient production of cold antihydrogen atoms in particle traps at CERN's Antiproton Decelerator opened up the possibility to perform direct measurements of Earth's gravitational acceleration on purely antimatter bodies. This is the goal of the AEgIS collaboration: measure the value of g using a pulsed source of cold antihydrogen and a moiré deflectometer/Talbot-Lau interferometer. The milestones achieved so far by AEgIS, on the way of developing a pulsed cold antihydrogen source using resonant charge-exchange between antiprotons and cold Rydberg positronium, are presented. Cold positronium was first formed at room temperature in a dedicated setup. The spectroscopy of its 1-3 and 3-15 transitions was carried out, demonstrating the feasibility of AEgIS' proof-of-concept in-flight laser excitation. Positronium was subsequently formed from the target at 10K temperature inside the 1T magnetic field of the experiment. In parallel, antiprotons were captured from the A.D. using aluminum degraders with 1.5% efficiency and cooled with electrons. These mixed e-/p+ plasma were radially compressed to sub-mm radii applying a rotating-wall drive and progressively reducing the number of cooling electrons. Antiprotons were finally transferred to the antihydrogen production trap with 70% efficiency using an in-flight launch and recapture procedure. Two further critical steps that are germane mainly to charge-exchange formation of antihydrogen - cooling of antiprotons and formation of a beam of antihydrogen - are being addressed in parallel. The coming of ELENA will allow, in the very near future, to increase the number of available antiprotons by up to a factor 50, overcoming the capture efficiency limitation of material degraders. This would be reflected in an increase of produced antihydrogen atoms of nominally the same factor, leading to a significative reduction of measurement times. 
Dr Michael Doser, CERN
Dr Michael Doser, CERNMichael Doser is a senior research physicist at CERN, the European Center for Nuclear Research in Geneva, Switzerland, who has specialized in working with antimatter, using it either as a tool (to study the strong interaction), or as an object of study itself (formation of anti-atoms, study of matter-antimatter asymmetry, measurement of the gravitational interaction between matter and antimatter). Since 2009, he is the spokesperson of the AEgIS experiment at CERN. He has been member of a number of scientific program committees and international organizing committees for scientific conferences, and for close to two decades has been an editor for the journal Physics Letters B, as well as of the bi-annual compendium of particle properties, the Review of Particle Properties." |
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| 14:30 - 14:45 | Discussion | |
| 15:00 - 15:30 |
The ASACUSA antihydrogen and hydrogen program: results and prospects
The goal of the ASACUSA CUSP collaboration at the Antiproton Decelerator of CERN is to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. A milestone was achieved in 2012 through the successful detection of 80 antihydrogen atoms 2.7 meters away from their production region. This was the first observation of “cold” antihydrogen in a magnetic field free region and opened the way toward precision spectroscopy of antimatter atoms in a beam. In parallel to the progress on the antihydrogen production, the spectroscopy beamline intended to be used for antihydrogen spectroscopy was tested with a source of hydrogen. This led to a measurement at a relative precision of 109 which constitues the most precise measurement of the hydrogen hyperfine splitting in a beam. This measurement also enabled to forecast the necessary conditions to achieve a measurement at the ppm level with antihydrogen. Unlike for hydrogen, the antihydrogen experiment is complicated by the difficulty of synthesizing enough cold antiatoms in ground state. A first measurement of the hyperfine splitting of antihydrogen with a precision 3 orders of magnitude worse than what was achieved with the same spectroscopy setup with hydrogen would however provide one of the most stringent CPT test on an absolute energy scale. My talk will present the latest developments and results with an emphasis on the spectroscopy apparatus. The coming years challenges within the ELENA era will also be discussed. 
Chloé Malbrunot, CERN, Switzerland
Chloé Malbrunot, CERN, SwitzerlandChloé Malbrunot is a CERN research staff since 2016. She completed her PhD in Particle Physics at TRIUMF in 2012. After a postdoc at the Austrian Academy of Science she became a CERN research fellow in 2013 and has since been working on two experiments at the CERN antiproton decelerator – ASACUSA and AEGIS. Both experiments aim at forming antihydrogen atoms and precisely measure their spectroscopic properties (ASACUSA) and test the effect of gravity on anti-matter (AEgIS). |
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| 15:30 - 15:45 | Discussion | |
| 15:45 - 16:30 |
Overview, closing remarks and perspective on future
Professor Klaus Jungmann, University of Groningen, Netherlands
Professor Klaus Jungmann, University of Groningen, NetherlandsKlaus Jungmann was educated at the University of Heidelberg, Germany, and earned a diploma in physics and a doctoral degree in 1985. He has been a postdoc at the IBM Almaden Research Laboratory in San Jose, USA. Back at Heidelberg from 1987 he became a research group leader and extraordinary professor of physics. He has led as a spokesperson for several international collaborations and he has contributed as a member to several high precision experiments in muon physics at PSI (Switzerland), RAL (UK), LAMPF (USA) and BNL (USA). Most precise values of fundamental constants have been obtained. Since 2001 he is full professor at the University of Groningen, Netherlands, where he was leading a national programme located at the Kernfysisch Versneller Institute (KVI) on precision experiments at the interfaces of atomic, nuclear and particle physics. He was scientific deputy director (2003-2008) and director (2009-2012) of KVI. He has been co-founder of the Van Swinderen institute for Particle Physics and Gravity (VSI) at the Faculty of Sciences and Engineering of the University of Groningen. VSI started in 2014 and it includes experimental as well as theoretical physics. Klaus Jungmann has been an invited keynote and plenary speaker at conferences covering atomic, nuclear and low energy particle physics and he has been active in both national and international collaboration and policy making committees as well as reviews. He has over 150 reviewed publications, more than 250 conference contributions and 225 invited lectures and colloquia. |