Most of us have learned in school or from books that all the materials around us — everything that we eat, drink, breathe, all living beings, the Earth itself — consists of atoms. They are of the order of 100 types, they are called "chemical elements" and are usually organized in the form of molecules, just as letters can be organized into words. We take these facts about our world as a matter of course, but at the end of the 19th century there was still heated debate on this issue. Only around 1900, when on the basis of several conclusions it became possible to calculate the size of the atoms, and when the electron, the subatomic particle inhabiting the edges of the atoms, was discovered, the atomic picture of the world finally formed.
But today, some parts of this picture are not quite clearly visible. Remains unsolved riddles in a hundred years. And all this hype about the “Higgs boson” is directly connected with these deep-seated questions that are in the very heart of our existence. Soon the vague parts of our picture can become clearer and reveal to us the details about our world, which are still unclear to us.
In school, we taught that the atom has a mass mainly due to its small nucleus. The electrons forming a blurred cloud around the nucleus add to this mass no more than one thousandth of it. But what they usually don’t tell us, unless they are deeply involved in physics, is that the size of an atom depends mainly on the mass of the electron. If you could somehow reduce the mass of the electron, you would find that the atoms grew and became more fragile. Reduce the mass of the electron a thousand times, and the atoms will become so fragile that even the heat left from the Big Bang can destroy them. Therefore, the entire structure and existence of ordinary materials is connected with the seemingly esoteric question: why do electrons have mass in general?
The mass of the electron and its origin have been baffled by physicists since its first measurement. Many discoveries related to other seemingly elementary particles made in the last hundred years have complicated and enriched this riddle. First, it was found that light also consists of particles called photons that have no mass at all. Then, that the atomic nucleus consists of particles called quarks, possessing mass. Recently we have found signs that neutrinos, elusive particles, in herds running from the depths of the Sun, also have a mass, albeit a very small one. Therefore, the question about the electron has moved into the category of larger questions: why do particles, such as electrons, quarks and neutrinos, have mass, but photons do not?
In the middle of the last century, physicists learned how to write equations predicting and describing the behavior of electrons. Although they did not know where the mass of the electron comes from, they found that this mass was quite easily incorporated into the equations manually, and decided that a full explanation of its origin would appear sometime later. But when they delved into the study of weak nuclear interactions, one of the four known ones in nature, they had a serious problem.
Physicists already knew that electrical forces were connected to photons, and then they realized that weak interaction was due to particles called “W” and “Z”. But at the same time, the W and Z particles had a difference from a photon in the form of a mass — they are comparable in mass with the tin atom, more than a hundred thousand times heavier than an electron. Unfortunately, physicists have found that they cannot inject the masses of the particles W and Z into the equations manually: the resulting equations gave meaningless predictions. And when they studied how weak interaction affects electrons, quarks and neutrinos, they found that the old way of introducing mass into the equations does not work — it also breaks the entire system.
To explain how well-known elementary particles can have mass, fresh ideas were required.
This riddle gradually became apparent in the 1950s and 1960s. And in the early 1960s, a possible solution emerged - here we get to know Peter Higgs and others (Braut, Englert, Guralnik, Hagen and Kibble). They suggested what we now call the "Higgs mechanism." Suppose, they say, there is another field in nature that is not yet known - like all fields, it is a kind of substance that exists in all areas of space - non-zero and uniform in all space and time. If this field — which is now called the Higgs field — is of the required type, its presence will cause the particles W and Z to manifest mass, and also allow physicists to return the electron mass to the equations. This will still postpone the question of why the electron mass is such, but at least then it will be possible to write equations in which the electron mass is not zero!
In the decades that followed, the idea of the Higgs mechanism was tested in various ways. Today, from the most detailed studies of W and Z particles, it is known that the solution to the riddle, which appeared due to weak interaction, lies somewhere in this area. But the details of this story are unknown to us.
What is a Higgs field, how to understand it? It is invisible to us and we do not feel it, as a child does not feel the air, or like a fish - water. And even more - because if we grow up, we become aware of the flow of air around our bodies and feel it with the help of touch, no our feelings give us access to the Higgs field. Not only can we not detect it with the help of feelings, we cannot do it directly and with the help of scientific tools. So how can we be sure that it exists? And how can we hope to learn something about him?
The analogy between the air and the Higgs field works well in the following example: if either of these two media is disturbed, they vibrate and create waves. It is easy to create such waves in the air - you can shout or clap your hands - and then our ears will find these waves in the form of sound. In the Higgs field, waves are harder and harder to observe. To do this, you need a giant particle accelerator, the Large Hadron Collider. And for their discovery you need scientific tools the size of a house, for example, ATLAS or CMS.
How it works? Clapping hands will surely create loud sound waves. The collision of two high-energy protons at the LHC will create very quiet Higgs waves, and this is not necessary - only one collision out of ten billion will result in this. The resulting wave will be the quietest of the possible waves in the Higgs field (in technical terms, one quantum of this type of wave). We call this wave the “Higgs particle” or the “Higgs boson”.
Sometimes the media calls it "a piece of God." This term was coined by one publisher to make his book sell better, so it comes from advertising, not science or religion. Scientists do not use this term.
Creating a Higgs particle is only part of the process and is relatively easy. Much harder to find it. Sound waves move freely from your palms across the room to the ear of another person. And the Higgs particle disintegrates into others faster than you can say the Higgs boson. In fact, faster than light takes to go through the diameter of an atom. ATLAS and CMS only carefully measure the remnants of an exploded Higgs particle and try to rewind what happened, like detectives, unraveling the evidence, to determine if the Higgs particle could be the source of these residues.
In fact, it is still more difficult. It is not enough to create one Higgs particle, since its remains cannot be distinguished. Often, the collision of two protons leads to the appearance of debris, resembling what results from the decay of the Higgs particle. So how do we establish that a Higgs particle has arisen? The key is that although Higgs particles are rare, their fragments appear quite regularly, while other processes occur frequently, but in a more random fashion. Just as your ear can recognize a singing voice even through heavy interference on the radio, experimenters can make out the regular ringing of the Higgs field among the random cacophony created by other similar processes.
Rotate all this is extremely difficult and difficult. But this was done in the framework of the triumph of human ingenuity.
Why was it to be engaged in such Hercules feats? Because of the extreme importance of the Higgs field for our very existence. Only our ignorance about its origin and properties can be compared with this importance in magnitude. We do not even know whether there is one such field; there may be several of them. The Higgs field may itself be a composite consisting of other fields. We do not know why it is non-zero, and we do not know why it interacts differently with different particles, and gives, say, an electron, a mass completely different from the mass of the upper quark. Since mass plays an important role not only in determining the size of atoms, but also in many other properties of nature, our understanding of the Universe and ourselves cannot be complete and satisfactory, as long as the Higgs field remains so mysterious. Studying the Higgs particles - waves in the Higgs field - will give us a deep knowledge of the nature of this field, just as one can learn about the air by sound waves, the stone by studying earthquakes, and the sea by watching the waves on the beach.
Some of you will surely (and fairly) ask: this is all very inspiring, but what benefits can it bring to society in a practical sense? You may not like the answer. History shows that the social benefits of research on fundamental issues may not manifest themselves for decades, even a century. I suspect that you used a computer today. I doubt that when Thompson discovered electrons in 1897, someone from his entourage could guess how much electronics could change society. We do not hope to present the technology of the next century, or how the seemingly esoteric knowledge gained today can affect the distant future. Investing in basic research is always a bit of a gamble, but on the basis of knowledge. In the worst case, we’ll learn something deep about nature that has unexpected consequences. Such knowledge, although not valuable in monetary terms, is priceless in both senses.
For the sake of brevity, I simplified something. It didn’t have to be that way. It was possible that the waves on the Higgs field could not be detected - this could resemble an attempt to create waves on an asphalt lake or in thick syrup. The waves could have subsided even before they were fully formed. But we know enough about the particles of nature to know that such an option would be possible only if there were other undiscovered particles and interactions — and some of them could certainly be found at the LHC. Or else a Higgs particle (s) could exist, but in such a way that it would be much more difficult to produce, or it could disintegrate in some unexpected way. In all such cases, it would have been a few more years before the Higgs field began to reveal its secrets. So we were ready to wait, although we hoped that we would not have to explain to the media all these difficulties.
But we were worried for nothing.
The discovery of the Higgs particle is a turning point in history. The triumph of those who proposed the Higgs mechanism and those that work for the LHC, ATLAS and CMS. But it does not mean the completion of our riddles connected with the mass of known particles — this is only the beginning of our hope to solve these riddles. In the future, the energy and the number of collisions at the LHC will increase, and ATLAS and CMS will comprehensively and systematically investigate the Higgs particle. What they learn may allow us to solve the riddles of this mass-producing ocean, in which we all swim, and will guide us further along an epic path that began more than a hundred years ago, which can take decades and centuries, and extends beyond our present horizons.