From about 1000 seconds (for a free neutron) to a negligible fraction of a second (from 10-24 to 10-22 s for resonances).
The structure and behavior of elementary particles is studied by the physics of elementary particles.
Everything elementary particles obey the principle of identity (all elementary particles of the same type in the Universe are completely identical in all their properties) and the principle of particle-wave dualism (each elementary particle corresponds to a de Broglie wave).
All elementary particles have the property of interconversion, which is a consequence of their interactions: strong, electromagnetic, weak, gravitational. The interactions of particles cause transformations of particles and their aggregates into other particles and their aggregates, if such transformations are not prohibited by the laws of conservation of energy, momentum, angular momentum, electric charge, baryon charge, etc.
Basic characteristics of elementary particles: lifetime, mass, spin, electric charge, magnetic moment, baryon charge, lepton charge, strangeness, isotopic spin, parity, charge parity, G-parity, CP-parity.
Classification
By life time
- Stable elementary particles - particles that have infinitely big time life in a free state (proton, electron, neutrino, photon and their antiparticles).
- Unstable elementary particles - particles that decay into other particles in a free state in a finite time (all other particles).
By mass
All elementary particles are divided into two classes:
- Massless particles are particles with zero mass (photon, gluon).
- Particles with non-zero mass (all other particles).
Largest back
All elementary particles are divided into two classes:
By types of interactions
Elementary particles are divided into the following groups:
Compound particles
- Hadrons are particles involved in all kinds of fundamental interactions. They consist of quarks and are subdivided, in turn, into:
- mesons - hadrons with integer spin, that is, they are bosons;
- baryons are hadrons with half-integer spin, that is, fermions. These include, in particular, the particles that make up the nucleus of an atom - the proton and the neutron.
Fundamental (structureless) particles
- Leptons are fermions that look like point particles (that is, they do not consist of anything) up to scales of the order of 10 −18 m. They do not participate in strong interactions. Participation in electromagnetic interactions was experimentally observed only for charged leptons (electrons, muons, tau leptons) and was not observed for neutrinos. There are 6 types of leptons.
- Quarks are fractionally charged particles that make up hadrons. They were not observed in the free state (a confinement mechanism was proposed to explain the absence of such observations). Like leptons, they are divided into 6 types and are considered structureless, however, unlike leptons, they participate in strong interactions.
- Gauge bosons are particles through which interactions are carried out:
- photon - a particle that carries electromagnetic interaction;
- eight gluons - particles that carry strong interactions;
- three intermediate vector bosons W + , W- and Z 0, carrying weak interaction;
- graviton is a hypothetical particle that carries gravitational interaction. The existence of gravitons, although not yet proven experimentally due to the weakness of the gravitational interaction, is considered quite probable; however, the graviton is not part of the Standard Model of elementary particles.
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Elementary particle sizes
Despite the wide variety of elementary particles, their sizes fit into two groups. The sizes of hadrons (both baryons and mesons) are about 10-15 m, which is close to the average distance between the quarks entering them. The sizes of fundamental, structureless particles - gauge bosons, quarks and leptons - agree within the experimental error with their point-like size (the upper limit of the diameter is about 10 −18 m) ( see explanation). If in further experiments the final sizes of these particles are not found, then this may indicate that the sizes of gauge bosons, quarks and leptons are close to the fundamental length (which very likely may turn out to be the Planck length equal to 1.6 × 10 −35 m) ...
It should be noted, however, that the size of an elementary particle is a rather complex concept, not always consistent with classical concepts. First, the uncertainty principle does not allow strictly localizing a physical particle. A wave packet representing a particle as a superposition of precisely localized quantum states always has a finite size and a certain spatial structure, and the size of the packet can be quite macroscopic - for example, an electron in an experiment with interference at two slits “senses” both slits of the interferometer, spaced at a macroscopic distance. Secondly, a physical particle changes the structure of the vacuum around itself, creating a "coat" of short-lived virtual particles - fermion-antifermion pairs (see Vacuum polarization) and bosons-carriers of interactions. The spatial dimensions of this region depend on the gauge charges possessed by the particle and on the masses of intermediate bosons (the radius of a shell of massive virtual bosons is close to their Compton wavelength, which, in turn, is inversely proportional to their mass). Thus, the radius of an electron from the point of view of neutrinos (only weak interaction is possible between them) is approximately equal to the Compton wavelength of W bosons, ~ 3 × 10 −18 m, and the size of the region of strong interaction of a hadron is determined by the Compton wavelength of the lightest of hadrons, pi-meson (~ 10 −15 m), acting here as a carrier of interaction.
History
Initially, the term "elementary particle" meant something absolutely elementary, the first brick of matter. However, when hundreds of hadrons with similar properties were discovered in the 1950s and 1960s, it became clear that at least hadrons have internal degrees of freedom, that is, they are not elementary in the strict sense of the word. This suspicion was further confirmed when it turned out that hadrons are composed of quarks.
Thus, physicists have advanced a little further into the structure of matter: leptons and quarks are now considered the most elementary, point-like parts of matter. For them (together with gauge bosons), the term “ fundamental particles ".
String theory, actively developed around the mid-1980s, assumes that elementary particles and their interactions are consequences of different types vibrations of especially small "strings".
Standard model
The standard model of elementary particles includes 12 fermion flavors, their corresponding antiparticles, as well as gauge bosons (photon, gluons, W- and Z-bosons), which transfer interactions between particles, and the Higgs boson discovered in 2012, which is responsible for the presence of inert mass in particles. However, the Standard Model is largely regarded as a temporal theory rather than truly fundamental, since it does not include gravity and contains several tens of free parameters (particle masses, etc.), the values of which do not directly follow from the theory. Perhaps there are elementary particles that are not described by the Standard Model - for example, such as the graviton (a particle that hypothetically carries gravitational forces) or supersymmetric partners of ordinary particles. In total, the model describes 61 particles.
Fermions
12 flavors of fermions are divided into 3 families (generations) of 4 particles each. Six of them are quarks. The other six are leptons, three of which are neutrinos, and the remaining three carry a unit negative charge: an electron, a muon, and a tau lepton.
| First generation | Second generation | Third generation |
|---|---|---|
| Electron: e - | Muon: μ − | Tau lepton: τ − |
| Electronic neutrino: ν e | Muon neutrino: ν μ | Tau neutrino: ν τ (\ displaystyle \ nu _ (\ tau)) |
| u-quark ("up"): u | c-quark ("charmed"): c | t-quark ("true"): t |
| d-quark ("down"): d | s-quark ("strange"): s | b-quark ("adorable"): b |
Antiparticles
There are also 12 fermionic antiparticles corresponding to the above twelve particles.
| First generation | Second generation | Third generation |
|---|---|---|
| positron: e + | Positive muon: μ + | Positive tau lepton: τ + |
| Electronic antineutrino: ν ¯ e (\ displaystyle (\ bar (\ nu)) _ (e)) | Muon antineutrino: ν ¯ μ (\ displaystyle (\ bar (\ nu)) _ (\ mu)) | Tau antineutrino: ν ¯ τ (\ displaystyle (\ bar (\ nu)) _ (\ tau)) |
| u-antiquark: u ¯ (\ displaystyle (\ bar (u))) | c-antiquark: c ¯ (\ displaystyle (\ bar (c))) | t-antiquark: t ¯ (\ displaystyle (\ bar (t))) |
| d-antiquark: d ¯ (\ displaystyle (\ bar (d))) | s-antiquark: s ¯ (\ displaystyle (\ bar (s))) | b-antiquark: b ¯ (\ displaystyle (\ bar (b))) |
Quarks
Quarks and antiquarks have never been found in a free state - this is explained by the phenomenon
An elementary particle is the smallest, indivisible particle that has no structure.
FUNDAMENTALS OF ELECTRODYNAMICS
Electrodynamics- a branch of physics that studies electromagnetic interactions. Electromagnetic interactions- interactions of charged particles. The main objects of study in electrodynamics are electrical and magnetic fields generated by electric charges and currents.
Topic 1. Electric field (electrostatics)
Electrostatics - a branch of electrodynamics that studies the interaction of stationary (static) charges.
Electric charge.
All bodies are electrified.
Electrifying a body means giving it an electric charge.
Electrified bodies interact - attract and repel.
The more electrified bodies are, the more they interact.
Electric charge is physical quantity, which characterizes the property of particles or bodies to enter into electromagnetic interactions and is a quantitative measure of these interactions.
The totality of all known experimental facts leads to the following conclusions:
· There are two kinds of electric charges, conventionally called positive and negative.
Charges don't exist without particles
· Charges can be transferred from one body to another.
· Unlike body weight, electric charge is not an integral characteristic of a given body. One and the same body under different conditions can have a different charge.
· The electric charge does not depend on the choice of the frame of reference in which it is measured. The electric charge does not depend on the speed of movement of the charge carrier.
· Like charges repel, unlike charges attract.
Measurement unit in SI - pendant
An elementary particle is the smallest, indivisible particle that has no structure.
For example, in an atom: electron ( , proton ( , neutron ( .
An elementary particle may or may not have a charge: , ,
Elementary charge - the charge belonging to an elementary particle, the smallest, indivisible.
Elementary charge - electron charge modulo.
The charges of an electron and a proton are numerically equal, but opposite in sign:
Electrification of tel.
What does “macroscopic body charged” mean? What determines the charge of any body?
All bodies are composed of atoms, which include positively charged protons, negatively charged electrons and neutral particles - neutrons . Protons and neutrons are part of atomic nuclei, electrons form the electron shell of atoms.
In a neutral atom, the number of protons in the nucleus is equal to the number of electrons in the shell.
Macroscopic bodies consisting of neutral atoms are electrically neutral.
An atom of a given substance can lose one or more electrons or acquire an extra electron. In these cases, a neutral atom turns into a positively or negatively charged ion.
Electrifying bodies– the process of obtaining electrically charged bodies from electrically neutral ones.
Bodies become electrified on contact with each other.
Upon contact, part of the electrons from one body is transferred to another, both bodies are electrified, i.e. receive charges equal in magnitude and opposite in sign:
"Excess" of electrons in comparison with protons creates a "-" charge in the body;
"Lack" of electrons in comparison with protons creates a "+" charge in the body.
The charge of any body is determined by the number of excess or insufficient electrons in comparison with protons.
Charge can be transferred from one body to another only in portions containing an integer number of electrons. Thus, the electric charge of a body is a discrete quantity that is a multiple of the charge of an electron:
Can you briefly and succinctly answer the question: "What is an electric charge?" It may seem simple at first glance, but in reality it turns out to be much more complicated.
Do we know what an electric charge is
The fact is that at the modern level of knowledge we still cannot decompose the concept of “charge” into simpler components. This is a fundamental, so to speak, primary concept.
We know that this is a certain property of elementary particles, the mechanism of interaction of charges is known, we can measure the charge and use its properties.
However, all this is a consequence of empirically obtained data. The nature of this phenomenon is still not clear to us. Therefore, we cannot unambiguously determine what an electric charge is.
For this it is necessary to reveal a whole range of concepts. Explain the mechanism of interaction of charges and describe their properties. Therefore, it is easier to understand what the statement means: "a given particle has (carries) an electric charge."
The presence of an electric charge on a particle
However, later it was possible to establish that the number of elementary particles is much greater, and that the proton, electron and neutron are not indivisible and fundamental building materials of the Universe. They themselves can decompose into components and turn into other types of particles.
Therefore, the name "elementary particle" now includes a fairly large class of particles, smaller in size than the atoms and nuclei of atoms. At the same time, particles can have a wide variety of properties and qualities.
However, such a property as an electric charge is of only two types, which are conventionally called positive and negative. The presence of a charge on a particle is its property to repel or be attracted to another particle, which also carries a charge. The direction of interaction in this case depends on the type of charges.
Charges of the same name are repelled, unlike charges are attracted. In this case, the force of interaction between the charges is very large in comparison with the gravitational forces inherent in all bodies without exception in the Universe.
In the hydrogen nucleus, for example, an electron carrying a negative charge is attracted to a nucleus consisting of a proton and carrying a positive charge, with a force 1039 times greater than the force with which the same electron is attracted by a proton due to gravitational interaction.
Particles may or may not be charged, depending on the type of particle. However, it is impossible to "remove" the charge from the particle, just as the existence of a charge outside the particle is also impossible.
In addition to the proton and the neutron, some other types of elementary particles carry a charge, however, only these two particles can exist for an indefinitely long time.
In the Universe, each body lives in its own time and the basic elementary particles also. The lifetime of most elementary particles is rather short.
Some disintegrate immediately after birth, which is why we call them unstable particles.
After a short time, they decay into stable ones: protons, electrons, neutrinos, photons, gravitons and their antiparticles.
The most important micro-objects in our near space are protons and electrons... Some of the distant parts of the Universe may consist of antimatter, the most important particles there will be antiproton and antielectron (positron).
In total, several hundred elementary particles have been discovered: proton (p), neutron (n), electron (e -), as well as photon (g), pi-mesons (p), muons (m), neutrinos of three types (electron ve, muonic vm, with lepton v t), etc. will obviously bring more new microparticles.
Particle Spawn:
Protons and electrons
The origins of protons and electrons date back to approximately ten billion years.
Another type of micro-objects that play an essential role in the structure of the near space - neutrons having common name with a proton: nucleons. By themselves, neutrons are unstable, they decay about ten minutes after they arise. They can be stable only in the atomic nucleus. A huge number of neutrons are constantly arising in the depths of stars, where the nuclei of atoms are born from protons.
Neutrino
The Universe also constantly produces neutrinos that are similar to an electron, but without charge and with low mass. In 1936, a kind of neutrino was discovered: muonic neutrinos, which arise when protons turn into neutrons, in the interiors of supermassive stars and during the decay of many unstable micro-objects. They are born when cosmic rays collide in interstellar space.
The Big Bang brought about the appearance of a huge number of neutrinos and muon neutrinos. Their number in space is constantly increasing, because they are not absorbed by practically any matter.
Photon
Like photons, neutrinos and muonic neutrinos fill the entire space. This phenomenon is called the "neutrino sea".
Since Big bang there are a great many photons left, which we call relict or fossil. The entire outer space is filled with them, and their frequency, and hence the energy, is constantly decreasing, as the Universe is expanding.
At present, all cosmic bodies, primarily stars and nebulae, participate in the formation of the photonic part of the Universe. Photons are born on the surface of stars from the energy of electrons.
Particle bonding
V initial stage formation of the Universe, all basic elementary particles were free. Then there were no nuclei of atoms, no planets, no stars.
Atoms, and of them planets, stars and all substances were formed later, when 300,000 years passed and the incandescent matter cooled down sufficiently during expansion. 
Only the neutrino, muonic neutrino and photon did not enter any system: their mutual attraction is too weak. They remained free particles.
Still on initial stage the formation of the Universe (300,000 years after its birth), free protons and electrons combined into hydrogen atoms (one proton and one electron, bound by electric force).
The proton is considered the main elementary particle with a charge of +1 and a mass of 1.672 · 10 −27 kg (slightly less than 2000 times heavier than an electron). The protons, trapped in a massive star, gradually turned into the main building "iron" of the Universe. At the same time, each of them released one percent of their rest mass. In supermassive stars, which at the end of their life are compressed into small volumes as a result of their own gravity, a proton can lose almost a fifth of its rest energy (and hence a fifth of its rest mass).It is known that the "building microblocks" of the Universe are protons and electrons.
Finally, when a proton and an antiproton meet, no system arises, but all their rest energy is released in the form of photons (). 
Scientists argue that as if there is also a ghostly basic elementary particle, graviton, which carries a gravitational interaction similar to electromagnetism. However, the presence of a graviton has been proven only theoretically.
Thus, our Universe, including the Earth, arose and now represent the main elementary particles: protons, electrons, neutrinos, photons, gravitons and many more open and undiscovered micro-objects.
« Physics - Grade 10 "
Let us first consider the simplest case, when electrically charged bodies are at rest.
The section of electrodynamics devoted to the study of the equilibrium conditions of electrically charged bodies is called electrostatics.
What is electrical charge?
What charges are there?
With words electricity, electric charge, electricity you have met many times and have gotten used to them. But try to answer the question: "What is an electric charge?" The very concept charge- this is a basic, primary concept, which at the present level of development of our knowledge is not reduced to any simpler, elementary concepts.
Let's try first to find out what is meant by the statement: “ This body or the particle has an electric charge. "
All bodies are built from the smallest particles, which are indivisible into simpler ones and therefore are called elementary.
Elementary particles have mass and due to this they are attracted to each other according to the law universal gravitation... As the distance between the particles increases, the gravitational force decreases in inverse proportion to the square of this distance. Most of the elementary particles, although not all, in addition, have the ability to interact with each other with a force that also decreases inversely with the square of the distance, but this force is many times greater than the force of gravity.
So in the hydrogen atom, shown schematically in Figure 14.1, an electron is attracted to the nucleus (proton) with a force 10 39 times greater than the force of gravitational attraction.
If particles interact with each other with forces that decrease with increasing distance in the same way as the forces of universal gravitation, but exceed the forces of gravity many times, then they say that these particles have an electric charge. The particles themselves are called charged.
There are particles without an electric charge, but there is no electric charge without a particle.
The interaction of charged particles is called electromagnetic.
Electric charge determines the intensity of electromagnetic interactions, just as mass determines the intensity of gravitational interactions.
The electric charge of an elementary particle is not a special mechanism in a particle that could be removed from it, decomposed into its component parts, and reassembled. The presence of an electric charge in an electron and other particles means only the existence of certain force interactions between them.
We, in essence, know nothing about the charge if we do not know the laws of these interactions. Knowledge of the laws of interactions should be part of our understanding of the charge. These laws are not easy, and it is impossible to summarize them in a few words. Therefore, it is impossible to give a sufficiently satisfactory short definition notion electric charge.
Two signs of electric charges.
All bodies have mass and therefore are attracted to each other. Charged bodies can both attract and repel each other. This the most important fact familiar to you means that in nature there are particles with electric charges of opposite signs; in the case of charges of the same sign, the particles are repelled, and in the case of different ones, they are attracted.
Elementary particle charge - protons, which are part of all atomic nuclei, are called positive, and the charge electrons- negative. There is no difference between positive and negative internal charges. If the signs of the charges of the particles were reversed, then the nature of the electromagnetic interactions would not change at all.
Elementary charge.
In addition to electrons and protons, there are several types of charged elementary particles. But only electrons and protons can exist indefinitely in a free state. The rest of the charged particles live for less than a millionth of a second. They are born in collisions of fast elementary particles and, having existed for a negligible time, decay, turning into other particles. You will get acquainted with these particles in the 11th grade.
Particles that have no electrical charge include neutron... Its mass only slightly exceeds the mass of a proton. Neutrons, together with protons, are part of atomic nucleus... If an elementary particle has a charge, then its value is strictly defined.
Charged bodies Electromagnetic forces in nature play a huge role due to the fact that electrically charged particles are part of all bodies. The constituent parts of atoms - nuclei and electrons - have an electrical charge.
The direct action of electromagnetic forces between bodies is not detected, since bodies in their normal state are electrically neutral.
The atom of any substance is neutral, since the number of electrons in it is equal to the number of protons in the nucleus. Positively and negatively charged particles are connected with each other by electric forces and form neutral systems.
A macroscopic body is electrically charged if it contains an excess amount of elementary particles with any one charge sign. So, the negative charge of the body is due to the excess of the number of electrons in comparison with the number of protons, and the positive charge is due to the lack of electrons.
In order to obtain an electrically charged macroscopic body, i.e. to electrify it, it is necessary to separate the part negative charge from the associated positive or transfer a negative charge to a neutral body.
This can be done using friction. If you brush through dry hair, then a small part of the most mobile charged particles - electrons will pass from the hair to the comb and charge it negatively, and the hair will be charged positively.
Equality of charges during electrification
With the help of experience, it can be proved that during electrification by friction, both bodies acquire charges that are opposite in sign, but have the same modulus.
Take an electrometer, on the rod of which a metal sphere with a hole is fixed, and two plates on long handles: one made of ebonite and the other made of plexiglass. When rubbing against each other, the plates become electrified.
Let's bring one of the plates inside the sphere without touching its walls. If the plate is positively charged, then part of the electrons from the arrow and the rod of the electrometer will be attracted to the plate and collect on the inner surface of the sphere. In this case, the arrow will be charged positively and repelled from the rod of the electrometer (Fig. 14.2, a).
If you bring another plate into the sphere, having previously removed the first one, then the electrons of the sphere and the rod will be repelled from the plate and accumulate in excess on the arrow. This will cause the arrow to deviate from the rod, and by the same angle as in the first experiment.
Having lowered both plates inside the sphere, we will not detect the deflection of the arrow at all (Fig. 14.2, b). This proves that the charges of the plates are equal in magnitude and opposite in sign.
Electrification of bodies and its manifestations. Significant electrification occurs when synthetic fabrics are rubbed. If you take off your shirt made of synthetic material in dry air, you can hear the characteristic crackling sound. Small sparks jump between the charged areas of the rubbing surfaces.
In printing houses, the paper becomes electrified during printing, and the sheets stick together. To prevent this from happening, special devices are used to drain the charge. However, the electrification of bodies in close contact is sometimes used, for example, in various electrocopy machines, etc.
Electric charge conservation law.
The experience with electrification of plates proves that during electrification by friction, the existing charges are redistributed between bodies that were previously neutral. A small part electrons are transferred from one body to another. At the same time, new particles do not appear, and previously existing ones do not disappear.
When bodies are electrified, electric charge conservation law... This law is valid for a system that does not enter from the outside and from which charged particles do not leave, i.e., for isolated system.
In an isolated system, the algebraic sum of the charges of all bodies is conserved.
q 1 + q 2 + q 3 + ... + q n = const. (14.1)
where q 1, q 2, etc. are the charges of individual charged bodies.
The charge conservation law has deep meaning... If the number of charged elementary particles does not change, then the fulfillment of the charge conservation law is obvious. But elementary particles can transform into each other, be born and disappear, giving life to new particles.
However, in all cases, charged particles are born only in pairs with charges of the same magnitude and opposite in sign; charged particles also disappear only in pairs, turning into neutral ones. And in all these cases, the algebraic sum of the charges remains the same.
The validity of the law of conservation of charge is confirmed by observations of a huge number of transformations of elementary particles. This law expresses one of the most fundamental properties of electric charge. The reason for the conservation of charge is still unknown.
