No abstract available

[en] 3 assumptions can explain why matter dominates antimatter. The first explanation is to think that matter and antimatter exist equally in the universe but are in 2 different places. We are in the part occupied by matter so naturally we don't find antimatter. The second explanation is to think that matter-anti-matter asymmetry was present at the very beginning of the universe and the third explanation is that something occurred shortly after the big-bang that favored matter at the expense of anti-matter. According to theory, all happened between 10^-35 seconds after the big-bang and 10^-11 seconds, the moment when the weak interaction and the strong interaction differentiated. The third explanation is certainly the most likely: a minimal excess of matter over antimatter is sufficient to explain today's situation. The existence of an initial excess of matter requires 3 conditions according to Sakharov's theory: first, some processes must violate the conservation of the baryonic charge, secondly C and CP symmetries must be broken in some processes and thirdly all that must have happened out of thermal balance. Particle accelerators can create and study anti-matter, the challenge was to keep anti-matter long enough to be able to study it. The Base experiment is able to keep an anti-proton for more than one year while the Alpha experiment can create and keep anti-hydrogen atoms for a quarter of an hour. Preliminary results have shown that the 2 first levels of electrons in hydrogen and those of anti-electrons in anti-hydrogen are identical which is consistent with the standard model. Other experiments like Base or Asacusa have shown no differences between matter and anti-matter. The next step will be to compare the effect of gravity on matter and anti-matter. (A.C.)

[en] In approaching the problem of the amount and astrophysical role of antimatter in the Universe, it is valuable to distinguish between two separate questions. First, must the universe be symmetric. Does an application of the microscopic laws of physics to the macroscopic scale of the Universe require that there be exactly equal numbers of particles and antiparticles. In contrast, is the Universe symmetric. The extent to which these questions can be or have been answered is the subject of this review. 2 tables, 118 refs

[en] The discussion of antiprotonic atoms covers exotic atoms, experimental results, analysis and interpretation of these results, and antiprotonium. (U.S.)

[en] Howard Gordon, a physicist from the U.S. Department of Energy's Brookhaven National Laboratory, and local educators will separate the science facts from the science fiction of 'Angels and Demons,' a major motion picture based on Dan Brown's best-selling novel. The film, which opens nationally in theaters today, focuses on a plot to destroy the Vatican using antimatter stolen from the Large Hadron Collider (LHC) at the European particle physics laboratory CERN. Speakers will explain the real science of the LHC, including antimatter - oppositely charged cousins of ordinary matter with intriguing properties.

[en] For the first time, an experiment has detected a slight difference of behavior between matter and anti-matter. The T2K (Tokai to Kamiokande) experiment in Japan has shown that neutrinos may oscillate more than anti-neutrinos. Other experiments at the CERN could bring a real revolution in anti-matter physics in a near future. 3 experiments (Gbar, Alpha-g and Aegis) will study how antimatter behaves in a gravity field. It is suspected that anti-matter could have a negative gravity which may help solve 3 important cosmological issues: the universe inflation, dark energy and dark matter. (A.C.)

[en] AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is an experiment that aims to perform the first direct measurement of the gravitational acceleration g of anti-hydrogen in the Earth's field. A cold anti-hydrogen beam will be produced by charge exchange reaction between cold antiprotons and positronium excited in Rydberg states. Rydberg positronium (with quantum number n between 20 and 30) will be produced by a two steps laser excitation. The anti-hydrogen beam, after being accelerated by Stark effect, will fly through the gratings of a 'moire' deflectometer. The deflection of the horizontal beam due to its free fall will be measured by a position sensitive detector. It is estimated that the detection of about 10³ anti-hydrogen atoms is required to determine the gravitational acceleration with a precision of 1%. In this report an overview of the AEgIS experiment is presented and its current status is described. Details on the production of slow positronium and its excitation with lasers are discussed. (authors)

[en] Anti-hydrogen experiments are currently based on non neutral electron, positron or antiproton plasma manipulation techniques in cylindrical Malmberg-Penning traps. An experimental study of a plasma manipulation technique based on off-axis diocotron displacement is presented. The use of the auto-resonant excitation of (1,0) diocotron mode of pure electron plasma allows a precise positioning of the plasma by moving it across the magnetic field and allows dumping such plasma in a desired angular position. The experimental procedure described here will pave the way to positron loading into an off-axial Penning trap terminated with a positronium converter target as it is proposed for the AEgIS experimental apparatus. The technique was studied over a range of confining magnetic field values and reproduces experimental conditions similar to most of the currently running anti-hydrogen experiments. The efficiency of the auto-resonant excitation - in terms of plasma expansion rate and particle loss - is analyzed, studying the behaviour of electron plasma subjected to large off-axial displacements, showing that this method fulfills the requirements imposed by the AEgIS experiment. (authors)

[en] This discussion between 2 physicists G. Chardin and L. Blanchet sheds light on a model of anti-gravitation for antimatter. According to the equivalence principle of general relativity, any body falls the same way in a gravitational field whatever its nature: matter or antimatter. This new model studies the consequences of a different behavior of antimatter when submitted to gravitation. A negative mass for antimatter could explain the acceleration of universe expansion without the need for a cosmological constant or black energy. This model gives the right age for the universe and can explain primordial nucleosynthesis on a longer time period: 40 years instead of 3 minutes for the standard model. The future experiments Gbar, Alpha-g and Aegis that will be performed at CERN, will clarify the behaviour of anti-hydrogen toward gravity, and will be a test of this new model. (A.C.)

[en] A popular pastime among amateur scientific historians is tracing key concepts in twentieth century physics back to their origins. Participants at the Antihydrogen Workshop in Munich on July 30-31 were astonished to hear 1989 Nobel prizewinner Wolfgang Paul mention in his introductory remarks that W. Nernst referred to antimatter as far back as 1897