Quarks, bosons and gluons - the standard model on the edge of the fork

Hear about quarks, the strong force and neutrons, and get a little lost? Here is an overview of the accepted theory in particle physics

In every field there is an accepted basic theory. In molecular biology you will find the central example, which explains the transition from nucleotides to proteins, in chemistry you will discover the periodic table and quantum mechanics, and in the physics of elementary particles you will be exposed to the standard model.

The standard model is the theoretical framework that explains the particles that exist in the universe and the interactions between them, or in other words, the forces acting between them.

particles

The standard model includes a certain number of particles, and each particle is coupled to an antiparticle. When a particle meets its antiparticle, both undergo annihilation and each valve turns into energy. Antiparticles are the same as all particles, but their charges are different. For example, the antiparticle of the electron is called a positron (usually the antiparticles are simply called antisomething, for example the antiparticle of a proton will be called an antiproton). It has the same mass as an electron, but its electric charge is positive. The existence of antimatter was theoretically predicted in 1928, and in 1932 the positron was discovered in cosmic rays, and today physicists at CERN laboratories are producing antihydrogen atoms. Just for general knowledge, antimatter is the most expensive material in the world. A gram of antimatter costs several thousand trillion dollars!

According to the standard model, the particles can be divided into several groups. The first division distinguishes between bosons and fermions. The bosons are particles with a complete spin (0,1,2...), and the fermions have a spin of half and its multiples (1/2,3/2...), where spin is a property of elementary particles, their internal angular momentum. Another difference between fermions and bosons is manifested in the fermions' compliance with Pauli's exclusion principle, which states that two particles with the same properties cannot be in the same quantum state. The bosons, on the other hand, are not subject to this prohibition.

It's time to meet the main players. We mentioned the division into fermions and bosons, and now we will explain which particles belong to which group. The bosons are the particles that carry the forces. This group includes the following particles (the column on the right side of the picture): the photon carries the electric force, the gluons carry the strong force, the Z and W carry the weak force and several additional Higgs particles (not shown in the picture), which should explain why particles have mass. Except for the Higgs, all the particles noted so far were discovered in the experiment.

Fermions are divided into two groups, quarks and leptons, with each group having six particles, which are divided into three "flavors" or generations. Each generation differs from the previous one in mass. The group of quarks includes six particles (the upper left part of the picture), whose names (translated into Hebrew) are: up, down, magical, strange, upper and lower (physicists have an interesting sense of humor...). Quarks have an electric charge of 2/3+ or 1/3- of the charge of the electron.

You are probably asking yourself how it is possible for a particle with a charge that is not an integer multiple of the charge of the electron, after all we have always learned that the charge of the electron is the elementary unit of charge in nature. Well, the quarks are always in structures, the sum of whose electric charge is a whole multiple of the charge of the electron. The general name for particles made of quarks is hadrons. The hadrons are divided into baryons and mesons, where the baryons are particles made up of three quarks, similar to protons and neutrons, and the mesons are particles made up of a quark and an antiquark. The proton, for example, is made up of three quarks: up, up and down. In the last year, more exotic particles, made of four and five quarks, were discovered.

The lepton group also includes six particles: the electron and its neutrino, the muon and its neutrino, and the tau and its neutrino. The leptons are not affected by the strong nuclear force. The muon and the tau are similar in their properties and electrical charge to the electron, but just larger. Regarding the valve of the neutrinos, the opinions are slightly divided. Until recently, they were thought to be massless. However, recent discoveries suggest that they have some small mass.
forces

The standard model currently includes three fundamental forces in nature, which are the electromagnetic force, the weak nuclear force and the strong nuclear force. The forces in the standard model are described as an exchange of boson particles.

The electromagnetic force is probably the most familiar force. Its carrier particle is the massless photon. Its range is infinite (remember Coulomb's law? F = kq1q2/r2) and it weakens with the square of the distance between the two particles involved.

The next force is the weak nuclear force. This is the force that is responsible, among other things, for radioactive decays. Its carrier particles are the W and the Z.

The third fundamental force is the strong nuclear force, known as the "color force". The model that describes it attaches to each particle that feels the force (these are quarks) a red, blue or green "color" (it is important to understand that this color has nothing to do with the concept of color we are familiar with. This is a model whose purpose is to explain the behavior of the particles). The way the force works is described as an exchange of gluon particles, when each quark emits a gluon that carries color and anti-color, and while emitting the gluon, the quark changes its color. This is how they constantly change colors. Same colors repel each other, while different colors attract each other.

A phenomenon related to the strong force is confinement, according to which in nature it is not possible to observe colored charged particles, that is, quarks can only be discovered in "colorless" structures. A colorless structure can be three quarks (red + blue + green = white) or a quark and an antiquark (color + anticolor = colorless).

And what about the dependence of the strong force on distance, you ask? Well, unlike the electromagnetic force, for example, whose strength decreases with increasing distance, the strength of the strong force decreases as the particles involved get closer. Admit it, sounds a bit strange. This means that when the particles are very, very close, the force between them tends to zero, and they behave almost like free particles! This is essentially asymptotic freedom, which states that the strength of the strong force between two particles, the distance between them tends to zero, also tends to zero, and they behave as particles free from the influence of the force.

In conclusion…

The Standard Model is the current theory in the field of elementary particles. It passed many experimental tests and managed to provide good and accurate predictions. Today, the standard model is considered almost complete in terms of experimental discoveries. The missing piece of the puzzle is the Higgs boson particle, which should explain why particles have mass.

Another unresolved question is the asymmetry between matter and antimatter. Although in principle they should behave exactly the same, and in the big bang equal amounts of both should have been created, this did not happen, and observations in experiments revealed a violation of this symmetry. There is a pretty conclusive proof of the asymmetry between matter and antimatter, and it is our very existence. Guess how exactly? Hint: Think about the ionization process mentioned earlier.

Despite the many successes of the standard model, many searches are underway, both among theorists and experimenters, for physics "beyond the standard model". These are new theories that want to replace or expand the standard model. We will briefly mention a few names, since any such theory could fill countless articles. One candidate is supersymmetry, which predicts the existence of a corresponding supersymmetric particle for every particle in the standard model. Another theory is the string theory, which holds that all the particles in our world are vibrations of tiny strings.

To test these theories and the standard model, various experiments are conducted around the world. Two of the most notable are the experiments that will be conducted in the LHC accelerator at CERN, which will begin operation in 2007. It will be the largest and most powerful accelerator in the world, with energies of 14 teU (more than any accelerator ever). In experiments at the LHC, physicists will search for elusive higgs, exotic supersymmetric particles, and possibly tiny black holes. For sure, it will be interesting.

The meaning of all this

Many of the readers must feel a little strange at the strange theories and amusing names. Try to remember that the purpose of theories is to explain and predict particle behavior. In the case of the "power of color" for example, the model manages to explain the behavior of power in simple and clear terms such as color. There is no doubt that the theory itself is much deeper, and it certainly includes a lot of mathematics and precise predictions, but there is great beauty in explaining the behavior of power in such a picturesque and simple way. As you can see, many times the reality is stranger than any imagination.

Take everything said in the article with a grain of salt and research the subject a little yourself, if you are interested. Nice links attached. This is only the tip of the iceberg of an interesting and intriguing field, which continues to develop. The purpose of the article was to provide a brief and general explanation of what is happening in the field of elementary particle physics and to stimulate the interest of the readers.
Questions and references to websites and answers can be directed to my email slartibartfastush@hotmail.com

Colorful Nobel Prize in Physics

What are the smallest building blocks in nature? How do these particles build all the matter around us? What forces work in nature, and what is their mode of action?

The 2004 Nobel Prize in Physics deals with these fundamental questions, problems that troubled the minds of physicists throughout the twentieth century and still continue to challenge theorists and experimentalists alike.

David Gross (Gross), David Politzer (Politzer) and Frank Wilczak (Wilczak) reached an important theoretical discovery regarding the strong force, known as the "color force". The strong force is the force that acts between the quarks inside the protons and neutrons and is responsible for the nucleus of the atom. The recipients of the award discovered a fact, which at first glance seemed contrary to common sense. The interpretation of the math results they made said that the closer two quarks are to each other, the weaker their "color charge" gets. When the quarks are really close together, the force is so weak that they behave almost like free particles. This phenomenon was named "asymptotic freedom". This behavior reverses as the particles move further apart. The power gets stronger as the distances increase. This behavior is similar to that of a rubber band. The tighter the rubber band, the greater the force.

Their discovery was summarized in 1973 in an elegant mathematical framework, which led to the birth of a completely new theory, called quantum chromodynamics (Quantum Chromo Dynamics) and QCD for short. This theory was an important contribution to the Standard Model, the theory that describes all physics related to the electromagnetic force (acting between charged particles), the weak nuclear force (which plays an important role in the Sun's energy production process) and the strong nuclear force (acting between quarks). With the help of QCD physicists can finally explain why quakers behave as free particles only at high energies. In protons and neutrons the quarks can only be found in triplets.

Thanks to their discovery, David Gross, David Pulitzer and Frank Wilczak brought physics one step forward on the way to realizing the great dream of building a unified theory, which also includes gravity - a theory of everything.

David Gross Born in 1941 (he is 63 years old today) in Washington, DC in the United States (Gross is a citizen of the United States). He received his doctorate in physics in 1966 from the University of California at Berkeley. He currently serves as a professor at the Kabali Institute for Theoretical Physics at the University of California at Santa Barbara in the United States.

David Pulitzer A citizen of the United States, he received his doctorate in physics in 1974 from Harvard University. He is currently a professor in the Department of Physics at the California Institute of Technology (Caltech) in Pasadena, California, United States.

Frank Wilczak Born in 1951 (now 53 years old) in Queens, New York in the United States (citizen of the United States). Received his doctorate in physics in 1974 from Princeton University. Currently serves as a professor of physics in the physics department at the Massachusetts Institute of Technology (MIT) in Cambridge, United States.

Recommended sites:

A particle adventure

The Atlas experiment

The accelerator at Fermi

The accelerator at Stanford

The quantum universe

The elegant universe plan