ON THE ROAD TO PHYSICS WITH ANTIHYDROGEN ATOMS


Winnipeg, June 14, 2004 - Scientists from Harvard University - USA, Forschungszentrum Juelich, Max-Planck-Institut fuer Quantenoptik in Garching, Ludwig-Maximilians-Universitaet in Munich - Germany and York University - Canada do research at CERN/Geneva aiming for the production of trappable antihydrogen atoms and the study of their physical characteristics.

Appropriately 100 years after the birth of Paul Dirac in 1902 - the researchers succeeded in producing thousands of "cold" antihydrogen atoms. Further progress towards the trapping of cold antihydrogen atoms has been made since, and will be presented at the Canadian Association of Physicists (CAP) Congress in Winnipeg on June 14, 2004 at 14:15 by Prof. Walter Oelert from the Research Centre Juelich in Germany on behalf of the ATRAP collaboration. The title of his talk is: "Observation of Cold Antihydrogen - Perspectives for Testing Fundamental Symmetries". The long term goal of the research is a very accurate spectroscopic measurement of antihydrogen - in comparison to hydrogen and the study of the gravitational force between matter and antimatter.

When (1996) the first observation of a few high-velocity atoms of antihydrogen was reported it was realised that these atoms where probably the most expensive stuff in the world; however, speculation on them for financial gain was not advised. Though being unrealistic, this substance is known as the dream material for rocket propulsion in science fiction movies. Antihydrogen is, however, most valuable for studies in science to answer fundamental questions of physics: symmetry, natural constants, gravity, and the existence of the universe consisitng solely of matter. Hydrogen is the simplest matter atom with an electron orbiting a proton. Antihydrogen atoms are the simplest antimatter atoms. The antihydrogen atom is formed when replacing the proton with its antimatter counterpart, the antiproton, and the electron with its antimatter counterpart, the antielectron or positron.

Using purely mathematical considerations Paul Dirac predicted the existence of the antielectron in the late 1920's. Since then it has become a well established fact that for each elementary particle - and thus for the constituent particles of matter atoms - there exists an antiparticle with equivalent properties such as mass but with opposite electrical charge.

Physics is an experimental science. Experiments have to demonstrate or disclaim the exact equivalence of matter and antimatter systems. Though presently accepted theorems in physics predict the identity of such systems, the inequality of matter and antimatter existence in the universe would require that differences between them exist or at least existed during the history of our universe.

The low energy antimatter research is performed at the European Research Centre CERN/Geneva in the Antiproton Decelerator (AD), the only machine in the world for such studies. Recent highlights were and will be reported:

1) Distribution of the antihydrogen atomic states populated via three body recombination and the observation of atomic states that survive an ionization field of 360 Volt/cm, and thus have a radius of 0.1 mu-m or less.

2) First measurements of the velocity of slow antihydrogen atoms. These experiments were made by varying the oscillating frequency of a stripping field. Fast antihydrogen atoms can pass through that field while it is low, while slower atoms are ionized. This first demonstration analyzed only the speeds of the most weakly bound antihydrogen atoms, and these atoms are moving faster than can be trapped.

3) An entirely new method for producing slow antihydrogen atoms was demonstrated. A pair of lasers selects the antihydrogen states that are produced, by exciting Cesium atoms, which then transfer an electron by resonant charge exchange collisions, first to produce positronium atoms and then to form antihydrogen atoms. The results are a clear proof of principle with a rate close to expectation. This method is a basic alternative insofar as the temperature of antihydrogen atoms produced can be much better controlled. This important research was proposed and developed by the Canadian colleagues within the ATRAP research group.

4) A quantitative analysis of the positron cooling of antiprotons and a method for measuring the density and spatial distribution of the trapped antiprotons and trapped positrons used to make slow antihydrogen was completed. This is crucial for quantitative understanding of antihydrogen production.

A comparison of the antimatter system with its normal matter partner would be the most stringent test of the "symmetry between matter and antimatter". This CPT symmetry theorem of physics predicts identical properties for matter and antimatter particles under the exchange of charge (C), the reflection in space (P) and reversal of time (T). Encouraged by the latest progress the scientists are eager to move forward in pursuit of the ambitious goal.

This release is given on the occasion of the presentation of the ATRAP results at the CAP congress. The content of the presentation is based on the scientific work of the ATRAP collaboration.

Figure Caption: During the experiments the trap electrodes for the interaction region and the antiproton trap dip into the top region of the fiber detector systems where the individual fibers are read out at the bottom via photomultipliers.

For images, please visit:
http://hussle.harvard.edu/~atrap/Figures/ATRAP_TRAP_HARVARD.jpg
http://hussle.harvard.edu/~atrap/Figures/ATRAP_Detector_Juelich_01.jpg
http://hussle.harvard.edu/~atrap/Figures/ATRAP_Detector_Juelich_02.jpg

CONTACT:

Professor Gerald Gabrielse (Spokesperson of the ATRAP collaboration)
Department of Physics
Harvard University
Cambridge, MA 02138
USA
Phone: +41 22 767 9813 or +41 792014281 or +41 22 76 79813
Email: gabrielse@physics.harvard.edu or gabrielse@hussle.harvard.edu

Professor Walter Oelert
IKP
Forschungszentrum Juelich GmbH
52425 Juelich
Germany
Phone: +49 2461 61 4156 (4402, 3091), or +41 22 76 79813 (75829)
Email: w.oelert@fz-juelich.de

Professor Theodor Haensch and Dr. Jochen Walz
Max-Planck-Institut fuer Quantenoptik
85748 Garching
Germany
and
Ludwig-Maximilians-Universitaet Muenchen
80799 Muenchen
Germany
Phone: +49 89 32905 281 or +41 22 76 79813 (71757)
Email: t.w.haensch@physik.uni-muenchen.de and jcw@mpq.mpg.de

Professor Eric Hessels
Dept. of Physics and Astronomy
York University
Toronto, ON
Canada, M3J 1P3
Phone: (416) 736 2100 x33040
Email: hessels@yorku.ca