Here he is finally here! The "divine particle" - a popular explanation of the Higgs boson

The 2013 Nobel Prize in Physics is awarded to François Englert and Peter Higgs, discoverers of the Braut-Englert-Higgs boson that broke the symmetry in nature and provides the other particles with the mass

The 2013 Nobel Prize in Physics was jointly awarded to François Englert and Peter Higgs for formulating the theory describing the mechanism by which particles obtain their mass. In 1964, the two researchers published their theory for the first time separately (Englert reached the conclusion jointly with his colleague Robert Braut who died last year and did not manage to win the Nobel Prize).

In 2012, the theory of the three was confirmed after the discovery of the Higgs particle at the CERN laboratory in Switzerland.

The mechanism on which the prize was awarded is a central part of the standard model of particle physics that describes how the world is built. According to the Standard Model, all things in the universe, from flowers and people to stars and planets, are made up of a small number of building blocks: the particles of matter. These particles are controlled by forces that mediate with the help of the force particles that ensure that everything works properly. The entire standard model also relies on the existence of a special type of particle: the Higgs particle. This particle is connected to an invisible field that fills all space - even when our universe seems to be empty, this field is there.

More on the subject on the science website

• 49 years after the prediction: Peter Higgs and Francois Engler win the Nobel Prize in Physics for the Higgs boson * Exclusive interview with Prof. Elam Gross
• Prof. Francois Engler, winner of the Nobel Prize in Physics, is also a researcher at the Tel Aviv School of Physics
• Prof. Elam Gross: It is possible to remove the uncertainty regarding the discovery of the Higgs particle

 

The Higgs boson (H) completes the standard model of particle physics that describes the building blocks of the universe. If it were not for the existence of this field, electrons and quarks would be massless, similar to photons, the particles of light, and just like them, and according to the predictions of Einstein's theory, they would move through space at the speed of light, without the possibility of being trapped inside atoms or molecules. In that case nothing of what we know would exist.

The two researchers, François Englert and Robert Braut, were young scientists when in 1964 they separately formulated the theory that saved the Standard Model from total collapse. Almost half a century later, on Wednesday the Fourth of July 2012, they were both in the audience at the European Laboratory for Particle Physics at the Sarn particle accelerator in Geneva, when the discovery of the Higgs boson that finally confirmed the theory was made public.

The model that created order

The idea that the entire universe can be described using a small number of building blocks is an ancient idea. As early as 400 BC, thinker Democritus assumed that everything is made up of atoms (átomos in Greek "indivisible"). Today we know that atoms can be divided. They are made up of the electrons orbiting the nucleus of the atom which itself is made up of neutrons and protons. And they, in turn, consist of even smaller particles called quarks (more on them on Wikipedia). In fact, only electrons and quarks are indivisible according to the standard model. The atomic nucleus consists of two types of quarks: an 'up' quark and a 'down' quark (up and down, respectively). So basically three elementary particles are needed for matter to exist: electrons, 'up' type quarks and 'down' type quarks. However, during the fifties and sixties of the last century, new particles were unexpectedly discovered both in the cosmic radiation in space and in particle accelerators that had been built a long time ago, so that the standard model had to include them in its framework.

Besides matter particles there are also force particles for each of the four forces in nature - gravity, electromagnetism, the strong force and the weak force. The first two forces on the list are the most familiar - they cause repulsion or attraction and we can see their effects with our own eyes. The strong nuclear force acts on the quarks and holds the protons and neutrons together in the atomic nucleus, while the weak nuclear force is responsible for radioactive decay, which is required, for example, for nuclear processes occurring in the core of the sun. The Standard Model of particle physics unites the basic building blocks of nature with three of the four known forces (the fourth force, gravity, remains, as yet, outside this model). The exact interplay of these forces has long been a mystery. For example, how does the piece of metal attracted to the magnet "know" that it is indeed there next to it? And how does the moon "feel" the earth's gravity?
Invisible fields fill the space

The explanation given by the physicists holds that space is full of many invisible fields. The gravitational field, the electromagnetic field, the quark field and all the other fields fill space, or in other words, the four dimensions of space-time, an abstract space in which the theory rules. The Standard Model includes a quantum field theory in which fields and particles are the essential building blocks of the universe.

In quantum physics, everything is treated as a collection of vibrations within the quantum fields. These vibrations are carried through the field in small and discrete packages called 'quanta', which appear to us as particles. There are two types of fields: matter fields with matter particles and force fields with force particles - the mediating factors that carry the force on them. The Higgs particle is also a vibration of its field - sometimes called the Higgs field.

Without this field the standard model would collapse like a house of cards since quantum field theory includes infinite values ​​required for restraint and symmetries that cannot be seen. It was only after the studies of François Englert and Robert Braut, and Peter Higgs, and then other researchers, who showed that the symmetry of the Standard Model could be broken without destroying the entire theory, that the theory was accepted.
This is in light of the fact that the standard model will only be true if the particles have no mass. As for the electromagnetic force that uses its massless photons as the force carriers, no such problem exists. The weak force, on the other hand, is mediated by three massive particles: two electrically charged particles of type W and one particle of type Z. They do not agree with the hypothesis regarding the nature of the massless photons - how is it possible that the electroweak force, which unites the electromagnetic force together With the weak force, exists? The validity of the standard model has become threatened. This is where the three researchers Englert, Braut and Higgs entered the picture with their ingenious mechanism in which the particles gain mass for themselves and thus saved the standard model.

A 'ghost'-like field - Higgs field

The Higgs field is unlike any other field in physics. All other fields are of variable strength and reach zero strength at their lowest energy level. This is not how the Higgs field behaves - even if the space were completely emptied of its contents, there would still be a ghost-like field that refuses to be extinguished: the Higgs field. We do not notice it; The Higgs field is like air to us, like water to fish. However, in its absence we would not exist at all since the particles obtain mass for themselves only after reacting with it. Particles that do not react with it do not gain mass for themselves, those that react with it weakly become light-mass and those that react with it strongly become heavy particles. For example, electrons that gain their valence from this field play a critical role in creation itself and in holding the atoms and molecules together. If the Higgs field suddenly disappears, all matter will collapse because the electrons that will instantly lose their valence will scatter everywhere at the speed of light.

So what makes the Higgs field special? It breaks the internal symmetry of the world. In nature, symmetry is a common feature - faces take and change shape frequently and flowers have different types of geometric symmetries. Physicists have managed to discover other types of symmetry that can describe our world, although these are types found at a deeper level. One of these symmetries, which is relatively simple, states that it does not matter to the results obtained whether the experiment was carried out in a laboratory in Stockholm or in Paris. And similarly, it doesn't matter when exactly the experiment was conducted. Einstein's theory of relativity refers to symmetries in space and time, and it became the model underlying other theories, such as the standard model of particle physics. The equations of this model are symmetric; Similar to the situation where a sphere looks the same from any angle we look at it, the equations of the standard model remain unchanged even if the viewing direction that defines them has changed.

The principles of symmetry also produced other, somewhat unexpected results. As early as 1918, the German mathematician Emmy Noether was able to show that the conservation laws of physics, for example the law of conservation of energy and the conservation of electric charge, originate in symmetry.

At the same time, symmetry dictates a number of requirements that must be fulfilled. A ball should be perfectly round; The smallest bump will break the spherical symmetry. Equations have other requirements. And one of the symmetry equations of the standard model prohibits the particles from gaining mass. However, we know that this is not true in our real world - so the particles must get their mass from another source. This is where the mechanism on which the Nobel Prize was awarded comes in, providing a way in which symmetry both exists and is not visible to the ordinary eye.

The symmetry is hidden from view but it is still there

Our universe was apparently born symmetrical - at the moment of the big bang all particles were massless and all forces were united into a single primordial force. This original order no longer exists - the symmetry of this situation was hidden from us. A certain event occurred already after 11-10 seconds from the moment of the big bang. The Higgs field has lost its original equilibrium. How did this happen?

Everything started symmetrically. This state can be described as a sphere in the center of a circular bowl, in its lowest energy state. After pushing it, the ball begins to roll, but after a while it returns to the lowest, most stable point from which it came.

However, if a bump appears in the center of the bowl, which now gives it the shape of a Mexican hat, the position in the center of the bowl will still be symmetrical, but it will become unstable. The ball will roll down in any direction. The hat is still symmetrical, but once the ball has rolled down, its location away from the center of the hat "hides" this symmetry. Similarly, the Higgs field broke its symmetry and "found" a stable energy level at a point far from its symmetric point of origin. This spontaneous symmetry breaking is also known as the 'phase transition of the Higgs field'; It's like the point where water freezes into ice.

In order for such a phase transition to occur, four particles were needed, but only one of them, the Higgs particle, survived. The other three particles disappeared after they transferred the mass property to the mediators of the weak force (two electrically charged particles of type W and one particle of type Z). In this way the symmetry of the electroweak force in the standard model was preserved - the symmetry between the three heavy particles of the weak force and the massless photon of the electromagnetic force remained, only now it is simply hidden from view.

Serious equipment for serious physics

The Nobel Prize winners probably did not believe that they would receive confirmation of their theory in their lifetime. The confirmation required a tremendous effort on the part of physicists from all over the world. For a long time, two laboratories competed with each other in the effort to discover the Higgs particle: Fermilab near Chicago, USA and CERN, on the France-Switzerland border. However, when the particle accelerator at Fermilab was shut down a few years ago, Sarn became the only place in the world where the hunt for the Higgs boson continued.

Seren was founded in 1954 in an attempt to promote pan-European research between the various European countries after World War II. It currently includes twenty countries, and enables researchers from hundreds of different countries around the world to collaborate with each other in research projects.
Saran's most impressive achievement, the LHC (Large Hadron Collider), which is the largest particle accelerator in the world, is probably the most complex machine ever built by mankind. Two research groups including about three thousand researchers will look for the smallest particles that exist with the help of two huge detectors - ATLAS and CMS. The detectors are located about a hundred meters underground and are able to measure 40 million particle collisions per second that occur in a circular tunnel that is 27 kilometers long.

Every ten hours, protons are injected into the accelerator, one beam in each direction. One hundred thousand billion protons are compressed together into one very thin beam - not an easy task at all, especially in light of the fact that protons, charged with a positive electric charge, tend to repel each other. These protons move at a speed equal to 99.99999% of the speed of light and collide when energy is stored in them in the amount of 4 teravolts and a total of 8 teravolts (1 teravolt = one thousand billion electrovolts). Although energy in the amount of 1 teravolt is not that great, and is more or less equal to the energy stored in a flying mosquito, but when the energy is compressed inside a single proton, and you have 500 trillion such protons moving at enormous speed in the accelerator, the energy stored in this beam is equal to the energy of a traveling train at full speed. In 2015 this amount of energy will double its value.

 

A puzzle within a puzzle

Experiments in the field of particles are sometimes compared to striking two Swiss watches against each other in order to check how they are constructed. However, the process is much more difficult than that since the particles the researchers are looking for are completely new - they were created as a result of the enormous energy that was released at the moment of the collision. According to Einstein's famous formula E=mc2 [energy is equal to mass times the square of the speed of light], mass is a form of energy. And the magic inherent in this equation is what allows, even for massless particles, to sometimes create something completely new at the moment of collision; As in the case where two photons collide and create an electron and its antiparticle, the positron, or when a Higgs particle is created following the collision of two gluons, given the sufficient amount of energy.

The protons are like little bags filled with other particles - quarks, anti-quarks and gluons. Most of them cross each other without causing any commotion; On average, every time two clusters of particles collide with each other, only twenty of them are head-on collisions. And only one collision in a billion is worth considering. It seems that this number is relatively low, but it must be remembered that every such collision gives rise to an explosion of about a thousand particles. At an energy of 125 GeV it turns out that the Higgs particle is a hundred times heavier than the mass of the proton and this is one of the reasons why it is so difficult to create it.

However, the experiments in this field have not yet been completed. The scientists at Sern hope to generate more breakthrough discoveries in the coming years. Although the discovery of the Higgs boson is a tremendous achievement - it is the missing piece in the mystery of the standard model - the standard model itself is not the last piece in the puzzle of the universe.

One of the reasons for this is the fact that the standard model treats certain particles, neutrinos, as massless particles, recent studies show that they may have a finite mass. Another reason is that the model refers to visible matter only, which corresponds to only a fifth of all the matter in the universe. The rest is what is known as 'black matter' whose nature is still unknown. This substance is unknown to us, but its influence exists and it is probably responsible for keeping the galaxies together and preventing them from separating from each other.

In all other respects, black matter does not react with visible matter. Admittedly, the Higgs particle is special; Perhaps he will allow us to make contact with the mysterious darkness. The scientists hope to capture, even for a fraction of a moment, the dark matter as they continue to hunt for unknown particles at the LHC particle accelerator for decades to come.

For the in-depth explanation on the Nobel Prize website

Prof. Francois Engler, winner of the Nobel Prize in Physics, is also a researcher at the Tel Aviv School of Physics	235
49 years after the prediction: Peter Higgs and Francois Engler win the Nobel Prize in Physics for the Higgs boson * Exclusive interview with Prof. Elam Gross