Tragic: The researchers did not detect the existence of antihydrogen atoms until they hit the wall of the experimental facility and were destroyed. The destruction of the antiproton produced four charged pions (yellow traces), and the destruction of the positron produced two photons (red traces). The red and yellow blocks are detectors. (Source: CERN)
An international research team at the European Nuclear Research Center CERN in Geneva can generate 50, 000 antihydrogen atoms within a few minutes. With this large amount of antimatter, the standard theory of particle physics will be tested. That could clarify the question of why there is virtually no antimatter in our universe. The researchers present the structure of their experiment ATHENA in a pre-publication of the journal Nature (DOI: 10.1038 / nature01096). According to the standard theory of particle physics, antimatter in a certain sense behaves exactly "mirror-image" to matter. This makes it extremely difficult to understand why our universe apparently consists exclusively of matter. Because according to this "mirror image theory" particles can only be generated together with their associated antiparticles of pure energy or destroyed to energy. How could it have come to the observed surplus of matter in our universe?

One possible answer to be tested at CERN would be a tiny deviation of antimatter from the mirror-image behavior asserted by standard theory. Antihydrogen is particularly suitable for this test because a certain property of the hydrogen atom is extremely well known.

In the hydrogen atom, an electron revolves around a proton. According to quantum mechanics, the electron can not move on arbitrary orbits around the proton, but only has specific orbits to choose from. The frequency with which the electron changes from the lowest to the highest level under certain conditions is known to within a trillionth of a percent.

The CERN physicists want to compare this frequency with the corresponding frequency in the antihydrogen atom. The accuracy of this comparison should be one to a trillion (a one with 18 zeros). To achieve this accuracy, the temperature of the antihydrogen must be close to absolute zero at minus 273 degrees Celsius. Because you can not just cool antihydrogen for obvious reasons? the electrons and protons of the atoms of the cooling medium would immediately destroy themselves together with the corresponding antiparticles of the antihydrogen? physicists produce antihydrogen even at this low temperature. display

Another experiment planned with antihydrogen is the general relativity test. One wants to know if antihydrogen atoms fall as fast as hydrogen atoms under the influence of gravity. With individual elementary particles such as electrons or positrons, such a test is difficult to carry out because these particles are deflected by the smallest electromagnetic fields due to their electric charge. On the other hand, the (anti) hydrogen atom is neutral to these fields.

Axel Tilleman


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