General

Why is there more matter than antimatter in the universe?

Why do we exist? This is perhaps the deepest question that may seem completely beyond the scope of elementary particle physics. But our new experiment at the CERN Large Hadron Collider brought us closer to the answer. To understand why we exist, we must first go 13.8 billion years ago, in the time of the Big Bang. This event produced an equal amount of the substance of which we are composed, and antimatter.

It is believed that each particle has a partner fromantimatter, which is almost identical to it, but has an opposite charge. When a particle and its antiparticle meet, they annihilate - disappear in a flash of light.

Where is all the antimatter?

Why is the universe we see composedentirely of matter, it is one of the greatest mysteries of modern physics. If once there was an equal amount of antimatter, everything in the Universe would have annihilated. And so, a recently published study seems to have found a new source of asymmetry between matter and antimatter.

Arthur Schuster was the first to speak about antimatter.In 1896, then in 1928, Paul Dirac gave her a theoretical justification, and in 1932 Karl Anderson discovered it in the form of antielectrons, which were called positrons. Positrons are born in natural radioactive processes, for example, the decay of potassium-40. This means that a regular banana (containing potassium) emits a positron every 75 minutes. He then annihilates with electrons in matter, producing light. Medical applications like PET scanners also produce anti-matter in a similar process.

The main building blocks of substance fromwhich atoms consist, are elementary particles - quarks and leptons. There are six types of quarks: upper, lower, strange, enchanted, true and beautiful. Similarly, there are six leptons: an electron, a muon, a tau, and three kinds of neutrinos. There are also anti-material copies of these twelve particles, which differ only in their charge.

Particles of antimatter in principle should beperfect mirror image of their usual satellites. But experiments show that this is not always the case. Take, for example, particles known as mesons, which consist of one quark and one antiquark. Neutral mesons have an amazing feature: they can spontaneously turn into their own anti-meson and vice versa. In this process, the quark turns into an antiquark, or an antiquark turns into a quark. However, experiments have shown that this can occur more often in one direction than in another - as a result of which matter becomes more with time than antimatter.

The third time - the magic

Among particles containing quarks, such asymmetriesdiscovered only in strange and beautiful quarks - and these discoveries have become extremely important. The very first observation of the asymmetry with the participation of strange particles in 1964 allowed theorists to predict the existence of six quarks - at a time when it was known that there were only three. The discovery of asymmetry in beautiful particles in 2001 was the final confirmation of the mechanism that led to the picture with six quarks. Both discoveries brought Nobel prizes.

Both strange and beautiful quarks carrynegative electric charge. The only positively charged quark that in theory should be able to form particles that can exhibit the asymmetry of matter and antimatter is charmed. The theory suggests that he does this, his effect should be insignificant and difficult to find.

But the LHCb experiment at the Large Hadronthe collider was able to observe such asymmetry in particles called D-mesons, which consist of enchanted quarks - for the first time. This was made possible thanks to the unprecedented number of charmed particles produced directly in collisions at the LHC. The result shows that the probability that this is a statistical fluctuation is 50 per billion.

If this asymmetry is not born from the samethe mechanism itself, which leads to the asymmetries of strange and beautiful quarks, remains space for new sources of matter-antimatter asymmetry, which can add to the general asymmetry of those in the Universe. And this is important, since several known cases of asymmetry cannot explain why there is so much matter in the Universe. One discovery with enchanted quarks will not be enough to fill this problem, but this is an important part of the puzzle in understanding the interaction of fundamental particles.

Next steps

This discovery will be followed by an increase in the numbertheoretical papers that help in interpreting the result. But more importantly, it will outline further tests to deepen the understanding of our discovery - and some of these tests are already underway.

In the coming decade, the upgraded LHCb experiment will increase the sensitivity of such measurements. It will be complemented by the Belle II experiment in Japan, which is just starting to work.

Antimatter also underlies a number of otherexperiments. Whole anti-atoms are produced at the CERN Anti-Proton Retarder, and they provide a variety of high-precision measurements. The AMS-2 experiment aboard the International Space Station is in search of antimatter of cosmic origin. A number of current and future experiments will be devoted to the question of whether there is an asymmetry of matter-antimatter among neutrinos.

Although we still can not fully unravelthe mystery of the asymmetry of matter and antimatter, our latest discovery opened the door to an era of precise measurements that may reveal unknown phenomena. There is every reason to believe that one day physicists will be able to explain why we are here at all.

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