Antimatter has a big secret, and this is how CERN scientists are trying to unravel it

One of the reasons that antimatter is so interesting not only to particle physicists, but also to people who are passionate about science, is that the tools we have still do not allow us to understand what role it played in the origin of the universe. However, the enigma does not end here; nor do we know what laws govern the fine line that delimits the imbalance between matter and antimatter in which we will investigate in the last section of this article.

Before proceeding further, it is worth stopping a moment to briefly review what antimatter is and what makes it so peculiar. In reality it is nothing more than a form of matter made up of antiparticles, which are particles with the same mass and spin as the particles with which we are familiar, but with the opposite electrical charge. In this way, the antiparticle of the electron is the positron or antielectron. And the antiparticle of the proton is the antiproton.

Antimatter has a surprising property: when it comes into direct contact with matter, they both annihilate, releasing a large amount of energy in the form of high-energy photons, as well as other possible particle-antiparticle pairs. It is currently being studied in many of the world’s leading particle physics specialized research centers in the hope that knowing it better will help us understand some of the mysteries of the cosmos that remain beyond our reach.

CERN has tools to create and manipulate antimatter

Its exotic nature has not prevented scientists from finding a way to obtain it in the laboratory in order to study it and learn more about its characteristics. CERN, which is currently the most advanced particle physics laboratory on the planet, has several experiments specifically designed to investigate the most hidden secrets of antimatter by resorting to very energetic interactions between the particles.

Two of the ones that have already given us some encouraging results, and are still very promising, are ALPHA-g and GBAR. Broadly speaking, in the first, scientists cause the collision of two beams of particles with a high level of energy to obtain an antihydrogen atom made up of an antiproton and a positron, in the same way as protium, which is the isotope of Hydrogen more abundant in nature, is made up of a proton and an electron.

One of the great challenges involved in manipulating antimatter is that, as we have seen, when it comes into contact with matter they both annihilate each other and release a lot of energy. This is the reason why researchers have been forced to devise strategies to keep the antimatter they obtain in the laboratory completely isolated for as long as possible. The most effective ploy is to confine it in a vacuum chamber to prevent it from coming into contact with matter, and fortunately they have already managed to keep it in this state for several minutes.

CERN’s ALPHA-g and GBAR experiments seek to better understand the interaction between antimatter and gravity

ALPHA-g ( Antihydrogen Laser Physics Apparatus-gravity ) studies something as interesting as the interaction that occurs between antimatter and gravity because it is not clear that it has the same characteristics that define the interaction between gravity and ordinary matter. On the other hand, GBAR ( Gravitational Behavior of Antimatter at Rest ) produces anti-ions, cools them until they reach a temperature close to absolute zero, which is -273.15 ° C, and then steals a positron from them to transform them into a non-anti-atom. ionic.

The purpose of these two experiments is to study the interaction of antimatter and gravity as thoroughly as possible, so scientists believe that approaching this task using two different perspectives can help them better understand this fundamental force, and, perhaps, to develop a quantum theory of gravity.

However, CERN’s efforts do not end here. At the end of last year the researchers of the BASE experiment ( Baryon Antibaryon Symmetry Experiment ) devised a surprising device designed to transport antiparticles. It sounds complex, and it also seems dangerous, but it is a very interesting idea because it would allow the antimatter obtained at CERN to be carried to other facilities where it could be studied.

Antimatter at CERN
In this photograph we can see in action one of the CERN technicians involved in the fine-tuning of the sophisticated equipment used in the BASE experiment (Baryon Antibaryon Symmetry Experiment).

This initiative is still under development, but, if all goes as the scientists have planned, it will facilitate collaboration between different institutions that have a common purpose: to better understand the properties of antimatter

The great enigma facing scientists: matter-antimatter asymmetry

And, finally, we come to the great mystery in which antimatter is involved, an enigma that possibly many of the people who are reading this article have heard about: the asymmetry between matter and antimatter.

The big bang model that astrophysicists work with predicts this asymmetry, which is nothing more than a divergence, possibly small if we stick to the cosmological scale, in the initial amounts of antimatter and matter. Presumably the latter had to be more abundant because, otherwise, what it tells us what we know is that we would not exist because the matter would have been annihilated by coming into contact with the primordial antimatter generated during the Big Bang.

The great challenge physicists face is that the standard model has not managed to explain this asymmetry, which, on the other hand, has been partially verified in the laboratory by identifying the violation of CP symmetry (if you want to know more about these experiments I suggest you take a look at this veteran but still valuable article by Francisco R. Villatoro ).

Fortunately, the effort that physicists are making in recent years is paying off in the form of hypotheses that are, to say the least, promising. One of the most interesting is based on the discovery of a meson that has the peculiar ability to change state spontaneously, altering its structure between matter and antimatter.

The oscillation of the ‘charm’ mesons may be the key to explain the matter-antimatter asymmetry of the universe that has made our existence possible

Mesons are subatomic particles belonging to the hadron family that are composed of the same number of quarks and antiquarks, which are held together thanks to the mediation of the strong nuclear force. The change of state that the scientists of the LHCb experiment have observed in the charm mesons may be the key to understanding the mechanism that explains the matter-antimatter asymmetry of the universe. 

There is no doubt that we are living an exciting time for all of us who are interested in particle physics and cosmology. We can be sure that more surprising discoveries will arrive in the coming years that will allow us to know a little better not only our origin, but also our place in the universe.

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