Will anti-apple fall towards the earth

Record at Cern: the coldest antiproton gas on earth

Is an anti-hydrogen atom simply a hydrogen atom in which the signs of the charge are reversed? To know it, it is necessary to be able to cool a gas of such atoms almost to absolute zero. The physicists of the CERN-ALPHA experiment are trying to do this, and they have just reached a new record: an antiproton gas at 9 Kelvin.

$ config [ads_text] not found

According to the known laws of physics, all phenomena are unchanged according to the so-called CPT symmetry. An apple and the earth must be attracted in the same way as an anti-earth and an anti-apple from antimatter. Likewise, an anti-apple should be drawn to the earth and fall in the same way as an apple. But is that true? To find out, you need anti-hydrogen gas. Credit: Cern-Abhijit Tembhekar (apple).

Discovery of antiparticles

By looking for a relativistic form of the Schrödinger equation for the electron, i.e. combining the laws of restricted larativity and the laws of quantum mechanics, the physicist Paul Diracfut leads to the discovery that it must exist in the world. Universe a twin particle for all known particles that only differ in the sign of the charge. This was the prediction of the existence of antimatter.

The antiparticle of the electron, lepositron, was first identified by Dirac Auproton. However, the latter knew that his equation implied that the electrons with a positive charge must have a similar element. Since he did not want to multiply the number of elementary particles known at the time, he thought that an unknown solution to this problem must exist. He had to admit that this was not possible when Carl Anderson discovered the positron in 1932. The latter actually had a mass identical to that of the electron.

One cannot avoid the conclusion that there must be an antimatter particle with a negative charge for the proton. The latter was discovered in 1955 by Emilio Segrè, Clyde Wiegand, Edward Lofgren, Owen Chamberlain and Thomas Ypsilantis. Named Antiproton, it won the 1959 Nobel Prize in Physics from Emilio Segrèet Owen Chamberlain.

Today antimatter and antiprotons are part of normal physicists. For example, beams of protons and antiprotons routinely collide with Tevatron. Antimatter has not yet delivered all of its secrets, however. In particular, we fail to understand why our observable universe is mostly made up of particles, while the laws of known physics imply that matter and antimatter should have been created in equal amounts at the time of the Big Bang. This is the problem with cosmic antimatter.

From left to right, Emilio Segrè, Clyde Wiegand, Edward Lofgren, Owen Chamberlain and Thomas Ypsilantis, the team members who discovered the antiproton. Credit: Lawrence Berkeley National Laboratory.

Some have long wondered whether antimatter and matter cannot repel due to an antigravity effect. One could perhaps also explain why our observable universe consists mainly of matter by assuming an early separation of matter and antimatter in certain zones of the cosmos under the effect of a hypothetical antigravity.

However, we can give theoretical and experimental arguments that are unfavorable for such a hypothesis, but a slight doubt remains. Therefore it would be interesting to have a large number of anti-hydrogen atoms and to check whether, like hydrogen atoms, they fall well into the earth's gravitational field, or whether they are repelled against it.

More generally, the problem of the absence of antimatter in the universe can mean that subtle differences exist between particles and particles that would not be identical to the signs of their charges. It has recently been shown that the antineutrin does not appear to have exactly the same properties as the neutrinos, although this has not really been proven yet.

If this were to happen, the foundations of the quantum theory of relativistic fields would have to be reconsidered because a famous theorem of the latter, CPT invariance, would be violated. The latter also implies that all properties of a hydrogen atom, its magnetic moment, its energy levels and its atomic transitions under the influence of laser radiation should not differ from those of a hydrogen atom.

More generally, this should apply to reactions between elementary particles under a combination of changes known as CPT lasymetry. If we find out, we should introduce a new type of physics, like string theory.

Temperature recording for an antiproton gas

Faced with such challenges, physicists set out in search of anti-hydrogen atoms. This was the case with the ATHENAauCern experiment, which was followed a few years ago by the ALPHA experiment (Anti-Hydrogen Laser Physics Apparatus).

The main problem is not so much the production of anti-hydrogen atoms, especially since we have long known positrons and antiprotons, which bind easily enough to form anti-atoms.

No, what is crucial is to be able to cool the atoms of the anti-hydrogen almost absolutely at a temperature on the order of 0.5K. The thermal movement of these atoms is then low enough to achieve one. English: www.dlr.de/en/desktopdefault.aspx/t…1_read-6388/ The German Society for Environmental Research (IKB) can carry out tests with the required precision, which go beyond the previously known limits of possible differences in the behavior of hydrogen and anti-hydrogen atoms, which are caused by a violation of the CPT symmetry.

We are not there yet ...

However, researchers of the ALPHA experiment have achieved a great achievement by using antiprotons to put into practice the technology that has already proven itself in the case of ultra-cold atoms of evaporative cooling.

About 40,000 antiprotons are formed first and some of the antiprotons can evaporate like the water molecules in a cup of coffee. In the end, only about 4,000 antiprotons gave up their energies to those who escaped the trap.

Whereas previously with antiprotons temperatures in the order of magnitude of 1000 K were reached, they succeeded in descending to 9 K, which corresponds to an increase of two orders of magnitude. The results obtained are in agreement with the predictions, and should be possible to fall further using this technique. These antiprotons can be used to form anti-hydrogen atoms that are cold enough to start experiments and look for signs of CPT injury.

In the meantime, the results of the ALPHA collaboration have been published.