Classification of elementary particles

How diverse elementary particles are, so are their characteristics as diverse. It is on the basis of characteristics that the classification of elementary particles is compiled.

One of the most important indicators is the mass. It is important to take into account the rest mass of the particle, since at the moment of movement, especially at high speeds, it increases significantly. Sometimes, without considering this fact, some scientists announced the discovery of new particles, although they dealt with the long-known. The unit of reference is considered to be the rest mass of the electron, since it is the lightest of them. In our time, the classification of elementary particles in accordance with their rest masses is as follows:

• Photons, which have no rest mass, since they constantly move with light speed;
• Light particles are leptons, which include neutrinos and electrons;
• Average particles that weigh from one electron mass to a thousand;
• Heavy - baryons, which have a mass of more than a thousand electron masses, which include neutrons, protons, hyperons.

The following characteristic, according to which the classification of elementary particles is created, is their electric charge. It is a multiple of the charge of one electron (-1) always. According to this characteristic, all particles are divided into positively charged, negatively charged and with zero charge. It is also assumed the existence of particles having a fractional charge.

Another characteristic by which the classification of elementary particles is created is the time of their life:

• Stable particles, to which the electron, neutrino, photon and proton belong, the neutron remains stable as long as it is in the atomic nucleus, and in the free state it decays within 15 minutes;
• Unstable particles - all the rest. Their lifetime is 10 (-10) - 10 (-24) seconds, and the particles with the shortest lifetime are resonances that are destroyed before they can leave the atomic nucleus or atom. They live 10 (-25) - 10 (-26) seconds. Although the existence of such particles was theoretically calculated, but practically no one recorded them. In the life of a person, the most important role belongs, of course, to stable particles, because it is from them that all macro-bodies are built.

The following classification characteristic is the type of interaction:

• Leptons are particles that participate only in weak and electromagnetic interactions;
• Hadrons are particles that, in addition to the above, also participate in strong interactions.

But the most important characteristic of elementary particles is the spin (the description of the particle momentum). Such a value in classical mechanics describes the characteristic of the rotation of a body. But physics, considering the properties of elementary particles, spin characterizes differently - as the internal degree of freedom of a given particle. It can only take positive values, which are proportional to the Planck constant, in contrast to the spin in mechanics, capable of taking any values. The coefficient expressing its proportionality is called the quantum spin number. For some particles, it can have integer (0, 1, 2), and in others - half-integer (1/2, 3/2) values. A particle with a 0-spin spin looks the same when it is rotated at any angle, with a spin of one - it takes on the same form after turning it 360 degrees, and from the spins to 2 - after a 180-degree turn, with a spin of ½ - At 720 degrees. All particles with a non-integral spin value are called fermions. These include all widely known particles, for example, protons, electrons, neutrons. Their backs are 1/2. And with integer ones, bosons. These substances, in fact, are quanta of fields, but even possessing corpuscular properties, still act as fields in the classical limit. A bright example of bosons is a photon with a spin of 1, as well as mesons with zero spin.