Physics lesson particle physics. Elementary particles and their properties

Municipal budgetary educational institution –

average secondary school No. 7 Belgorod

Open lesson in physics

11th grade

« Elementary particles»

Prepared and conducted:

physics teacher

Polshchikova A.N.

Belgorod 2015

Topic: Elementary particles.

Lesson type: lesson of studying and primary consolidation of new knowledge

Teaching method: lecture

Form of student activity: frontal, collective, individual

Objective of the lesson: expand students’ understanding of the structure of matter; consider the main stages in the development of elementary particle physics; give the concept of elementary particles and their properties.

Lesson objectives:

Educational : to introduce students to the concept of an elementary particle, the typology of elementary particles, as well as methods for studying the properties of elementary particles;

Developmental: develop cognitive interest students, ensuring their feasible involvement in active cognitive activity;

Educational: education of universal human qualities - awareness of perception scientific achievements in the world; developing curiosity and endurance.

Equipment for the lesson:

Didactic materials: textbook material, cards with tests and tables

Visual aids: presentation

Lesson progress

(Presentation)

1. Organization of the beginning of the lesson.

Teacher's activities: Mutual greetings between the teacher and students, fixing students, checking students’ readiness for the lesson. Organization of attention and inclusion of students in the business rhythm of work.

Predicted student activity: organizing attention and inclusion in the business rhythm of work.

2. Preparation for the main stage of the lesson.

Teacher's activities: Today we will begin to study a new section of “Quantum Physics” - “Elementary Particles”. In this chapter we will talk about the primary, indecomposable particles from which all matter is built, about elementary particles.

Physicists discovered the existence of elementary particles when studying nuclear processes, so until the middle of the 20th century, elementary particle physics was a branch of nuclear physics. Currently, particle physics and nuclear physics are close but independent branches of physics, united by the commonality of many problems considered and the research methods used.

The main task of elementary particle physics is the study of the nature, properties and mutual transformations of elementary particles.

It will also be our main task in studying the physics of elementary particles.

3. Assimilation of new knowledge and methods of action.

Teacher's activities: Lesson topic: "Stages of development of elementary particle physics." In this lesson we will look at the following questions:

The history of the development of ideas that the world consists of elementary particles

What are elementary particles?

How can one obtain an isolated elementary particle and is it possible?

Typology of particles.

The idea that the world consists of fundamental particles has long history. Today, there are three stages in the development of elementary particle physics.

Let's open the textbook. Let's get acquainted with the names of the stages and time frames.

Stage 1. From electron to positron: 1897 - 1932.

Stage 2. From positron to quarks: 1932 - 1964.

Stage 3. From the quark hypothesis (1964) to the present day.

Teacher's activities:

Stage 1.

Elementary, i.e. the simplest, further indivisible, this is how the famous ancient Greek scientist Democritus imagined the atom. Let me remind you that the word “atom” in translation means “indivisible”. For the first time, the idea of ​​the existence of tiny, invisible particles that make up all surrounding objects was expressed by Democritus 400 years BC. Science began to use the concept of atoms only in early XIX century, when on this basis it was possible to explain a whole series chemical phenomena. And at the end of this century it was discovered complex structure atom. In 1911, the atomic nucleus was discovered (E. Rutherford) and it was finally proven that atoms have a complex structure.

Let's remember guys: what particles are part of the atom and briefly characterize them?

Predicted student activity:

Teacher's activities: guys, maybe some of you remember: by whom and in what years were the electron, proton and neutron discovered?

Predicted student activity:

Electron. In 1898, J. Thomson proved the reality of the existence of electrons. In 1909, R. Millikan first measured the charge of an electron.

Proton. In 1919, E. Rutherford, while bombarding nitrogen with particles, discovered a particle whose charge was equal to the charge of an electron, and whose mass was 1836 times greater than the mass of the electron. The particle was named proton.

Neutron. Rutherford also suggested the existence of a chargeless particle whose mass is equal to the mass of a proton.

In 1932, D. Chadwick discovered the particle that Rutherford had suggested and called it the neutron.

Teacher's activities: After the discovery of the proton and neutron, it became clear that the nuclei of atoms, like the atoms themselves, have a complex structure. The proton-neutron theory of the structure of nuclei arose (D. D. Ivanenko and V. Heisenberg).

In the 30s of the 19th century, in the theory of electrolysis developed by M. Faraday, the concept of -ion appeared and the elementary charge was measured. The end of the 19th century - in addition to the discovery of the electron, was marked by the discovery of the phenomenon of radioactivity (A. Becquerel, 1896). In 1905, the idea of ​​electromagnetic field quanta - photons (A. Einstein) arose in physics.

Let's remember: what is a photon?

Predicted student activity: Photon (or quantum electromagnetic radiation) is an elementary light particle, electrically neutral, devoid of rest mass, but possessing energy and momentum.

Teacher's activities: open particles were considered indivisible and unchangeable primary essences, the main building blocks of the universe. However, this opinion did not last long.

Stage 2.

In the 1930s, the mutual transformations of protons and neutrons were discovered and studied, and it became clear that these particles are also not the unchanging elementary “building blocks” of nature.

Currently, about 400 subnuclear particles are known (the particles that make up atoms, which are usually called elementary). The vast majority of these particles are unstable (elementary particles transform into each other).

The only exceptions are the photon, electron, proton and neutrino.

Photon, electron, proton and neutrino are stable particles (particles that can exist in free state unlimited time), but each of them, when interacting with other particles, can turn into other particles.

All other particles undergo spontaneous transformations into other particles at certain intervals, and this main fact their existence.

I mentioned one more particle - the neutrino. What are the main characteristics of this particle? By whom and when was it discovered?

Predicted activity of the student: Neutrino is a particle devoid of electric charge and its rest mass is 0. The existence of this particle was predicted in 1931 by W. Pauli, and in 1955, the particle was experimentally registered. Manifests itself as a result of neutron decay:

Teacher's activities: Unstable elementary particles differ greatly in their lifetimes.

The longest-lived particle is the neutron. The neutron lifetime is about 15 minutes.

Other particles “live” for a much shorter time.

There are several dozen particles with a lifetime exceeding 10 -17 With. On the scale of the microcosm, this is a significant time. Such particles are calledrelatively stable .

Majority short-lived elementary particles have lifetimes of the order of 10-22 -10 -23 s.

The ability for mutual transformations is the most important property of all elementary particles.

Elementary particles are capable of being born and destroyed (emitted and absorbed). This also applies to stable particles, with the only difference being that transformations of stable particles do not occur spontaneously, but through interaction with other particles.

An example would beannihilation (i.e. disappearance ) electron and positron, accompanied by the birth of high-energy photons.

A positron is (an antiparticle of an electron) a positively charged particle that has the same mass and the same (in absolute value) charge as an electron. We'll talk about its characteristics in more detail in the next lesson. Let's just say that the existence of the positron was predicted by P. Dirac in 1928, and discovered in 1932 in cosmic rays K. Anderson.

In 1937, particles with a mass of 207 electron masses were discovered in cosmic rays, calledmuons ( -mesons ). Average life time-meson is equal to 2.2 * 10-6 s.

Then in 1947-1950 they openedpeonies (i.e. -mesons). Average lifetime of neutral-meson - 0.87·10 -16 s.

In subsequent years, the number of newly discovered particles began to grow rapidly. This was facilitated by research into cosmic rays, the development of accelerator technology and the study of nuclear reactions.

Modern accelerators are necessary to carry out the process of creating new particles and studying the properties of elementary particles. The initial particles are accelerated in the accelerator to high energies “on collision courses” and in certain place collide with each other. If the energy of the particles is high, then during the collision process many new particles, usually unstable, are born. These particles, scattering from the point of collision, disintegrate into more stable particles, which are recorded by detectors. For each such act of collision (physicists say: for each event) - and they are recorded in thousands per second! -experimenters as a result determine kinematic variables: the values ​​of the impulses and energies of the “caught” particles, as well as their trajectories (see figure in the textbook). By collecting many events of the same type and studying the distributions of these kinematic quantities, physicists reconstruct how the interaction occurred and what type of particles the resulting particles can be attributed to.

Stage 3.

Elementary particles are combined into three groups: photons , leptons And hadrons (Appendix 2).

Guys, list me the particles belonging to the group of photons.

Predicted student activity: To the group photons refers to a single particle - a photon

Teacher's activities: the next group consists of light particlesleptons .

: this group includes two types of neutrinos (electron and muon), electron and?-meson

Teacher's activities: Leptons also include a number of particles not listed in the table.

Third large group made up of heavy particles called hadrons. This group is divided into two subgroups. Lighter particles form a subgroup mesons .

Predicted student activity: the lightest of them are positively and negatively charged, as well as neutral -mesons. Pions are quanta of the nuclear field.

Teacher's activities: second subgroup -baryons - includes heavier particles. It is the most extensive.

Predicted student activity: The lightest baryons are nucleons - protons and neutrons.

Teacher's activities: they are followed by the so-called hyperons. Omega-minus-hyperon, discovered in 1964, closes the table.

The abundance of discovered and newly discovered hadrons led scientists to believe that they were all built from some other more fundamental particles.

In 1964, the American physicist M. Gell-Man put forward a hypothesis, confirmed by subsequent research, that all heavy fundamental particles - hadrons - are built from more fundamental particles calledquarks.

From a structural point of view, the elementary particles that make up atomic nuclei (nucleons), and in general all heavy particles - hadrons (baryons and mesons) - consist of even simpler particles, which are usually called fundamental. In this role of truly fundamental primary elements of matter are quarks, the electric charge of which is equal to +2/3 or -1/3 of the unit positive charge of a proton.

The most common and light quarks are called up and down and are designated, respectively, u (from English up) and d (down). Sometimes they are also called proton and neutron quarks due to the fact that the proton consists of a combination of uud, and the neutron - udd. The top quark has a charge of +2/3; bottom - negative charge -1/3. Since a proton consists of two up and one down, and a neutron consists of one up and two down quarks, you can independently verify that the total charge of the proton and neutron is strictly equal to 1 and 0.

Two other pairs of quarks are part of more exotic particles. Quarks from the second pair are called charmed - c (from charmed) and strange - s (from strange).

The third pair consists of true - t (from truth, or in the English tradition top) and beautiful - b (from beauty, or in the English tradition bottom) quarks.

Almost all particles consisting of various combinations of quarks have already been discovered experimentally.

With the acceptance of the quark hypothesis, it was possible to create a harmonious system of elementary particles. Numerous searches for quarks in the free state, carried out at high-energy accelerators and in cosmic rays, have been unsuccessful. Scientists believe that one of the reasons for the unobservability of free quarks is perhaps their very large masses. This prevents the birth of quarks at the energies that are achieved in modern accelerators.

However, in December 2006, a strange message about the discovery of “free top quarks” was broadcast across scientific news agencies and the media.

4. Initial check of understanding.

Teacher's activities: so guys, we've covered:

main stages in the development of particle physics

found out which particle is called elementary

got acquainted with the typology of particles.

In the next lesson we will look at:

more detailed classification of elementary particles

types of interactions of elementary particles

antiparticles.

And now I suggest you take a test to revive in your memory the main points of the material we have studied (Appendix 3).

5. Summing up the lesson.

Teacher's activities: Giving grades to the most active students.

6. Homework

Teacher's activities:

1. § 114 - 115

2. abstract.

Lesson No. 67.

Lesson topic: Problems of elementary particles

Lesson objectives:

Educational: to introduce students to the concept of an elementary particle, with the classification of elementary particles, to generalize and consolidate knowledge about fundamental types of interactions, to form scientific worldview.

Educational: to form a cognitive interest in physics, instilling love and respect for the achievements of science.

Educational: development of curiosity, ability to analyze, independently formulate conclusions, development of speech and thinking.

Equipment: interactive whiteboard(or a projector with a screen).

Lesson type: learning new material.

Lesson type: lecture

Lesson progress:

Organizational stage

Studying a new topic.

In nature, there are 4 types of fundamental (basic) interactions: gravitational, electromagnetic, strong and weak. According to modern ideas, interaction between bodies is carried out through the fields surrounding these bodies. The field itself in quantum theory is understood as a collection of quanta. Each type of interaction has its own interaction carriers and comes down to the absorption and emission of corresponding light quanta by particles.

Interactions can be long-range (manifest at very long distances) and short-range (manifest at very short distances).

Gravitational interaction occurs through the exchange of gravitons. They have not been detected experimentally. According to the law discovered in 1687 by the great English scientist Isaac Newton, all bodies, regardless of shape and size, attract each other with a force directly proportional to their mass and inversely proportional to the square of the distance between them. Gravitational interaction always leads to the attraction of bodies.

Electromagnetic interaction is long-range. Unlike gravitational interaction, electromagnetic interaction can result in both attraction and repulsion. The carriers of electromagnetic interaction are quanta of the electromagnetic field - photons. As a result of the exchange of these particles, electromagnetic interaction arises between charged bodies.

Strong interaction is the most powerful of all interactions. It is short-range, the corresponding forces decrease very quickly as the distance between them increases. The radius of action of nuclear forces is 10 -13 cm

The weak interaction occurs at very short distances. The range of action is approximately 1000 times less than that of nuclear forces.

The discovery of radioactivity and the results of Rutherford's experiments convincingly showed that atoms are composed of particles. They have been found to consist of electrons, protons and neutrons. At first, the particles from which atoms are built were considered indivisible. That's why they were called elementary particles. The idea of ​​a “simple” structure of the world was destroyed when in 1932 the antiparticle of the electron was discovered - a particle that had the same mass as the electron, but differed from it in the sign of the electric charge. This positively charged particle was called a positron... according to modern concepts, every particle has an antiparticle. The particle and antiparticle have the same mass, but opposite signs all charges. If the antiparticle coincides with the particle itself, then such particles are called truly neutral, their charge is 0. For example, a photon. When a particle and antiparticle collide, they annihilate, that is, they disappear, turning into other particles (often these particles are a photon).

All elementary particles (which cannot be divided into components) are divided into 2 groups: fundamental (structureless particles, all fundamental particles at this stage of development of physics are considered structureless, that is, they do not consist of other particles) and hadrons (particles with a complex structure).

Fundamental particles, in turn, are divided into leptons, quarks and carriers of interactions. Hadrons are divided into baryons and mesons. Leptons include the electron, positron, muon, taon, and three types of neutrinos.

Quarks are the particles that make up all hadrons. Participate in strong interactions.

According to modern concepts, each of the interactions arises as a result of the exchange of particles, called carriers of this interaction: a photon (a particle that carries the electromagnetic interaction), eight gluons (particles that carry the strong interaction), three intermediate vector bosons W + , W− and Z 0, carrying the weak interaction, graviton (carrier of gravitational interaction). The existence of gravitons has not yet been proven experimentally.

Hadrons participate in all types of fundamental interactions. They consist of quarks and are divided, in turn, into: baryons, consisting of three quarks, and mesons, consisting of two quarks, one of which is an antiquark.

The strongest interaction is the interaction between quarks. A proton consists of 2 u quarks, one d quark, a neutron consists of one u quark and 2 d quarks. It turned out that at very short distances none of the quarks notice their neighbors, and they behave like free particles that do not interact with each other. When quarks move away from each other, an attraction arises between them, which increases with increasing distance. To split hadrons into individual isolated quarks would require a lot of energy. Since there is no such energy, the quarks turn out to be eternal prisoners and forever remain locked inside the hadron. Quarks are held inside the hadron by the gluon field.

III. Consolidation

Option 1.

Option 2.

3.. How long does a neutron live outside an atom nucleus? A. 12 min B. 15 min

Lesson summary. During the lesson we got acquainted with the particles of the microworld and found out which particles are called elementary.

D/z§ 9.3

Particle name Mass (in electronic masses) Electric charge Life time (s) Antiparticle Stable Neutrino electron Stable Neutrino muon Stable Electron Stable Pi mesons ≈ 10 –10 –10 –8 Eta-null-meson Stable Lambda hyperon Sigma hyperons Xi-hyperons Omega-minus-hyperon

III. Consolidation

Name the main interactions that exist in nature

What is the difference between a particle and an antiparticle? What do they have in common?

Which particles participate in gravitational, electromagnetic, strong and weak interactions?

Option 1.

1. One of the properties of elementary particles is the ability……… A. to transform into each other B. to spontaneously change

2. Particles that can exist in a free state for an unlimited time are called..... A. unstable B. stable.

3. Which particle is stable? A. proton B. meson

4. A long-lived particle. A. neutrino B. neutron

5. Neutrinos are produced as a result of the decay of..... A. electron B. neutron

Option 2.

What is the main factor in the existence of elementary particles?

A. their mutual penetration B. their mutual transformation.

2. Which of the elementary particles is not isolated into a free particle. A. pion B. quarks

3. How long does a neutron live outside an atom nucleus? A. 12 min B. 15 min

Which particle is not stable? A. photon B. lepton

Are there immutable particles in nature? A. yes B. no

Molyanova Nadezhda Mikhailovna ID 011

Topic: The origins of particle physics. Classification of elementary particles.

The main content of the educational material:
- Historical stages of development of elementary particles.
- The concept of elementary particles and their classification, mutual transformations.
- Types of interactions of elementary particles.
- Elementary particles in our life.

Lesson type: generalization and systematization.

Lesson format: Lecture with elements of conversation and independent work students with a textbook and tables. (The tables are on the students’ tables and projected on the screen during the lesson)

Objective of the lesson:
- Expand students’ understanding of the structure of matter, give a classification of elementary particles, their general properties, introduce the main stages of development.
- Develop students’ scientific thinking based on ideas about elementary particles and their interactions

Lesson progress:
1. Organizational moment(1 min.)
2. Learning new material (30 min.)
3. Consolidation of learned knowledge (6 min.)
4. Summing up (2 min.)
5. D/Z (1 min.)

1. Today in the lesson we will talk about the primary, indecomposable particles that make up all matter. You are already more or less familiar with the electron, photon, proton and neutron. But what is an elementary particle?

2. The historical stages of development of elementary particles can be presented in the form of a table.

At the beginning of the 20th century, it was discovered that all atoms are built from neutrons, protons and electrons. Positrons, neutrinos, photons (gamma quantum) were discovered.
Basic characteristics of the most common elementary particles.

Elementary particles, in the precise sense of the word, are the primary, further indecomposable particles from which all substances are composed.
Currently this term is used for large group microparticles that are NOT atoms or nuclei, with the exception of the proton, which is both an elementary particle and the nucleus of a light hydrogen atom.
Elementary particles are characterized by the following parameters: " particle rest mass, spin value, electric charge value, lifetime."
The spin of an elementary particle is equal to the ratio of Planck's constant to 2 n

Particles having spin, etc. are called bosons ; with half-integer spin - fermions , i.e. all elementary particles are divided into particles and antiparticles. They have the same masses, spins, lifetimes and electric charges of equal magnitude.

The positron was discovered in a cloud chamber in 1928. This particle is an electron, but with a positive charge, the positron was discovered in cosmic rays. Later, during the interaction of gamma quanta with matter and in the reaction of converting a proton into a neutron.

The process of interaction of an elementary particle with an antiparticle, as a result of which they turn into other particles or quanta of an electromagnetic field, is called annihilation (disappearance). Annihilation reaction:

The reverse process of annihilation is called birth of a couple .

Question: Think about what structure antideuterium will have?
Answer: consists of an electron and a nucleus (proton and neutron). An antideuterium atom will consist of an antinucleus (an antiproton and an antineutron) and one positron moving around the antinucleus.

Elementary particles participate in four known fundamental types of interaction: strong, electromagnetic, weak and gravitational. (see table 3)


The energies of fundamental interactions are approximately as follows:

Let's look at Table 4
Question: Name the main classes of elementary particles.

Answer: photons, leptons, mesons, baryons.

Question: Name the main characteristics of elementary particles.
Answer: Mass, charge, spin, lifetime.

Question: How are particles and antiparticles different?
Answer: The signs of the electric charges of the particle and antiparticle are opposite.

Photons– particles participating in electromagnetic and gravitational interactions.
Leptons– particles that do not participate in strong interactions, but are capable of the other three.
Hadrons– particles participating in all types of fundamental interactions. This class includes baryons and mesons. Baryons have half-integer spins, and mesons have integer spins. Belonging to a baryon is marked by assigning a baryon charge - a number equal to +1 for a particle, and -1 for an antiparticle. Hadrons include only part of the mesons (P-meson). Nucleons are classified as baryons. Baryons whose mass is greater than the mass of a nucleon are called hyperons.
Belonging to leptons is marked by assigning a leptonic charge to each particle: +1 for particles, -1 for antiparticles.
It has been established that hadrons consist of quarks– six particles having a fractional elementary electric charge. Quarks have not been observed in a free state; they are found only in the very center of the nucleon as independent particles.
In order to penetrate deeper into the microworld, it is necessary to use particles of increasingly higher energies.
It turns out that with the enormous energy existing at temperature, weak and electromagnetic interactions combine into electroweak interactions. When all four interactions are combined, it becomes possible to transform particles of physical matter (fermions) into particles that are carriers of interaction (bosons).
Why is information about elementary particles so necessary?
The most important thing for particle physics is the conclusion about the relationship between mass and energy. The energy of a body or system of topics is equal to the mass multiplied by the square of the velocity.
Something to think about!
A neutrino is a particle that appeared at the moment of the birth of the Universe and carries a lot of information, so neutrino telescopes “catch” particles and scientists study them. There is a positron tomograph device. A radioactive element is introduced into the blood of a living organism, emitting positrons, which react with the body’s electrons, annihilate, and emit gamma rays, which are detected by a detector.
In small doses, gamma rays have a certain benefit on living organisms. Field of application: medicine, science, technology.

3. Using supporting notes, textbook, tables, give answers to questions.

4. All elementary particles transform into each other, i.e. these mutual transformations are the main factor in their existence. Among the properties of elementary particles, the following can be distinguished: instability, interconvertibility and interaction, the presence of an antiparticle in each particle, complex structure, classification.

The world consists of fundamental particles. Any material body has mass. What is mass? The LHC is a particle accelerator that allows physicists to penetrate deeper into matter than ever before.
The creation of the LHC marks the beginning of future advanced research. Researchers hope for new physical phenomena, such as the elusive Higgs particles, or those that form dark matter, making up most of the matter in the Universe. It is impossible to accurately predict the results of the upcoming experiments, but they will definitely have a great impact and not only on particle physics! But the creation of the LHC does not end a page in the history of physics, but rather marks the beginning of future promising research.

5. Homework (on the board)
Paragraphs 115, 116; reference summary
prepare a progress report research work on BAK.

Literature used:
Physics 11 G.Ya. Myakishev, B.B. Bukhovtsev. Bustard.
Physics course. Volume 3 K.A. Putilov, V.A. Fabrikant.
Atomic and nuclear physics. OK. Costco.
Lesson developments in physics. 11th grade. V.A.Volkov.
Uroki. Net

Goal: To tell students about elementary particles, their basic properties and classifications

Lesson progress

New material (given in lecture)

Studies of the structure of the atom and the atomic nucleus have shown that the composition of the atom includes electrons, protons, and neutrons. It was customary to call these particles elementary. Photon(), positron (e +) and neutrino (v), which are directly related to the atom and nucleus, also began to be called elementary particles.

According to the original plan, elementary particles are the simplest particles, from which the substance (atoms) of the existing world is built.

Elementary particles were initially imagined as something eternal, unchanging, indestructible, and the image of an elementary particle was associated with the image of a grain of sand or a structureless small ball.

Nowadays there is no clear criterion for elementaryness. The concept of "elementary particle" is very complex these days.

Let us briefly list the known elementary particles in the order of their historical discovery.

Methodological notes: Students are asked to fill out the following table at the time of further explanation (Appendix 1)

What type does it belong to?	Particle name	Designation	Opening year	Charge q	Particle mass

The electron was discovered by J.J. Thomsan in 1897. The masses of other elementary particles are usually expressed through the mass of the electron.

In 1900 M. Planck and especially, in 19005. A. Einstein showed that light consists of separate portions - photons. A photon has no charge, and its rest mass = 0. A photon can only exist in the process of moving at the speed of light.

Rutherford's experiments on particle scattering in 1911. Led to the discovery of the proton. Proton mass=1836m e

Most physicists were confident that they had finally managed to reduce the entire diversity of chemical elements and substances of nature to two simple entities: electrons and protons. The picture drawn by the physicists of those years on the structure of matter instilled a sense of scientific beauty and grace. In the period from 1911 By 1932 Many scientists were filled with a sense of satisfaction that they were able to fulfill the centuries-old dream of scientific research.

However, in 1928 P. Dirac, and subsequently in 1932 K. Anderson discovered such particles, called positrons(e+)

The positron is the first elementary particle predicted theoretically.

In 1932 D. Chadwig discovered a neutron with mass = 1838 m e

A neutron in a free state, unlike a proton, is unstable and decays into a proton and an electron with a half-life T = 1.01 10 3 s. Inside the nucleus, a neutron can exist indefinitely.

In 1931-1933. W. Pauli, analyzing -decay, suggested that during decay, in addition to the proton and electron, another neutral particle with rest mass = 0 is emitted. This particle was called neutrino()

Only in 1956 K. Cowan and his colleagues discovered an antineutrino() produced in nuclear reactor. It was “caught” when studying the reaction: p+ v n+e + , the neutrino causes the reaction n+p+e - .

In 1937 K. Anderson and S. Nedderman discovered charged particles with a mass of 206.7m e, these particles were called -mesons (+ and -), having a charge of +e and -e. Currently, these particles are called -particles or -muons.

In 1947 English scientists S. Powell, G. Occhialini and others discovered -mesons (-meson is the primary meson, which, when decaying, gives muons)

The meson has a charge of +e and -e, and a mass of 273.2 m e. Somewhat later than 1950, a neutral -meson (o) was discovered, with a mass of 264.2 m e. Currently, three types of -meson are known: -, o, + , they interact intensively with nucleons and are easily created when nucleons collide with nuclei, i.e. are nuclear active. It is currently believed that -mesons are nuclear field quanta responsible for the bulk of nuclear forces.

From 1949-1950 A literal “invasion” of elementary particles began, their number rapidly increasing.

The newly appeared particles can be divided into two groups:

The first group includes particles with masses of about 966 m e and 974 m e, currently called K-mesons. K + and K - mesons are known with masses of approximately 966.3 m e and electric charges +e and -e. Neutral K-mesons (K o and K o) with masses of 974.5 m e are known.

The second group of particles is called hyperons. The following hyperons are currently known:

In 1955 The antiproton was discovered, and in 1956 the antineutron was discovered.

For recent years new quasiparticles (resonance states) with an unusually short lifetime were discovered, on the order of 10 -22 - 10 -23 sec. In this case, it is not even possible to record traces of particles and their existence can be judged only from indirect considerations, from an analysis of the behavior of their decay.

In recent years, a second type of neutrino has been discovered, the so-called muon neutrino (antineutrino) and, which is emitted, for example, during the decay of -mesons;

III group- heavy particles, or baryons

This group includes:

• Nucleons and their antiparticles
• Hyperons and their antiparticles

Application of thermonuclear energy using the example of the Tokamak installation

Students are asked to answer the questions:

• Which nuclear reaction called thermonuclear? (orally)
• How can a thermonuclear reaction be carried out?
• Explain the principle of operation of the Tokamak installation. (in writing, using additional literature)
• Explain the principle of operation of a laser installation for thermonuclear fusion" (in writing, using additional literature)

Physicists discovered the existence of elementary particles when studying nuclear processes, so until the middle of the 20th century, elementary particle physics was a branch of nuclear physics. Currently, elementary particle physics and nuclear physics are close but independent branches of physics, united by the commonality of many problems considered and the research methods used. The main task of elementary particle physics is the study of the nature, properties and mutual transformations of elementary particles.
The idea that the world is made of fundamental particles has a long history. For the first time, the idea of ​​the existence of the smallest invisible particles that make up all surrounding objects was expressed 400 years BC by the Greek philosopher Democritus. He called these particles atoms, that is, indivisible particles. Science began to use the idea of ​​atoms only at the beginning of the 19th century, when on this basis it was possible to explain a number of chemical phenomena. In the 30s of the 19th century, in the theory of electrolysis developed by M. Faraday, the concept of an ion appeared and the elementary charge was measured. The end of the 19th century was marked by the discovery of the phenomenon of radioactivity (A. Becquerel, 1896), as well as the discoveries of electrons (J. Thomson, 1897) and alpha particles (E. Rutherford, 1899). In 1905, the idea of ​​electromagnetic field quanta - photons (A. Einstein) arose in physics.
In 1911, the atomic nucleus was discovered (E. Rutherford) and it was finally proven that atoms have a complex structure. In 1919, Rutherford discovered protons in the fission products of atomic nuclei of a number of elements. In 1932, J. Chadwick discovered the neutron. It became clear that the nuclei of atoms, like the atoms themselves, have a complex structure. The proton-neutron theory of the structure of nuclei arose (D. D. Ivanenko and V. Heisenberg). In the same 1932, a positron was discovered in cosmic rays (K. Anderson). A positron is a positively charged particle that has the same mass and the same (modulo) charge as an electron. The existence of the positron was predicted by P. Dirac in 1928. During these years, the mutual transformations of protons and neutrons were discovered and studied, and it became clear that these particles are also not the unchanging elementary “building blocks” of nature. In 1937, particles with a mass of 207 electron masses, called muons (μ-mesons), were discovered in cosmic rays. Then, in 1947–1950, pions (i.e., π mesons) were discovered, which, according to modern concepts, interact between nucleons in the nucleus. In subsequent years, the number of newly discovered particles began to grow rapidly. This was facilitated by research into cosmic rays, the development of accelerator technology and the study of nuclear reactions.
Currently, about 400 subnuclear particles are known, which are commonly called elementary. The vast majority of these particles are unstable. The only exceptions are the photon, electron, proton and neutrino. All other particles undergo spontaneous transformations into other particles at certain intervals. Unstable elementary particles differ greatly in their lifetimes. The longest-lived particle is the neutron. The neutron lifetime is about 15 minutes. Other particles “live” for a much shorter time. For example, the average lifetime of a μ meson is 2.2·10–6 s, and that of a neutral π meson is 0.87·10–16 s. Many massive particles - hyperons - have an average lifetime of the order of 10–10 s.
There are several dozen particles with a lifetime exceeding 10–17 s. On the scale of the microcosm, this is a significant time. Such particles are called relatively stable. Most short-lived elementary particles have lifetimes of the order of 10–22–10–23 s.
The ability to undergo mutual transformations is the most important property of all elementary particles. Elementary particles are capable of being born and destroyed (emitted and absorbed). This also applies to stable particles, with the only difference being that transformations of stable particles do not occur spontaneously, but through interaction with other particles. An example is the annihilation (i.e., disappearance) of an electron and a positron, accompanied by the birth of high-energy photons. The reverse process can also occur - the birth of an electron-positron pair, for example, when a photon with a sufficiently high energy collides with a nucleus. Such dangerous double What a positron is for an electron, is also for a proton. It's called an antiproton. The electric charge of the antiproton is negative. Currently, antiparticles have been found in all particles. Antiparticles are opposed to particles because when any particle meets its antiparticle, their annihilation occurs, i.e., both particles disappear, turning into radiation quanta or other particles.
The antiparticle has even been found in the neutron. The neutron and antineutron differ only in the signs of the magnetic moment and the so-called baryon charge. The existence of antimatter atoms is possible, the nuclei of which consist of antinucleons, and the shell of positrons. When antimatter annihilates with matter, the rest energy is converted into the energy of radiation quanta. This is enormous energy, significantly exceeding that released during nuclear and thermonuclear reactions.
In the variety of elementary particles known to date, a more or less harmonious classification system is revealed. In table 9.9.1 provides some information about the properties of elementary particles with a lifetime of more than 10–20 s. Of the many properties that characterize an elementary particle, the table shows only the particle’s mass (in electron masses), electric charge (in units of elementary charge) and angular momentum (the so-called spin) in units of Planck’s constant ħ = h / 2π. The table also shows the average particle lifetime.
Group
Particle name
Symbol
Mass (in electronic masses)
Electric charge
Spin
Life time (s)
Particle
Antiparticle
Photons
Photon
γ

Stable
Leptons
Neutrino electron
νe

1 / 2
Stable
Neutrino muon
νμ

1 / 2
Stable
Electron
e–
e+

–1 1
1 / 2
Stable
Mu meson
μ–
μ+
206,8
–1 1
1 / 2
2,2∙10–6
Hadrons
Mesons
Pi mesons
π0
264,1

0,87∙10–16
π+
π–
273,1
1 –1

2,6∙10–8
K-mesons
K+
K –
966,4
1 –1

1,24∙10–8
K 0

≈ 10–10–10–8
Eta-null-meson
η0

≈ 10–18
Baryons
Proton
p

1836,1
1 –1
1 / 2
Stable
Neutron
n

Lambda hyperon
Λ0

1 / 2
2,63∙10–10
Sigma hyperons
Σ +

2327,6
1 –1
1 / 2
0,8∙10–10
Σ 0

1 / 2
7,4∙10–20
Σ –

2343,1
–1 1
1 / 2
1,48∙10–10
Xi-hyperons
Ξ 0

1 / 2
2,9∙10–10
Ξ –

2585,6
–1 1
1 / 2
1,64∙10–10
Omega-minus-hyperon
Ω–

–1 1
1 / 2
0,82∙10–11

Table 9.9.1.
Elementary particles are combined into three groups: photons, leptons and hadrons.
The group of photons includes a single particle - a photon, which is the carrier of electromagnetic interaction.
The next group consists of light leptonic particles. This group includes two types of neutrinos (electron and muon), electron and μ-meson. Leptons also include a number of particles not listed in the table. All leptons have spin
The third large group consists of heavy particles called hadrons. This group is divided into two subgroups. Lighter particles make up a subgroup of mesons. The lightest of them are positively and negatively charged, as well as neutral π-mesons with masses of the order of 250 electron masses (Table 9.9.1). Pions are quanta of the nuclear field, just as photons are quanta of the electromagnetic field. This subgroup also includes four K mesons and one η0 meson. All mesons have a spin equal to zero.
The second subgroup - baryons - includes heavier particles. It is the most extensive. The lightest baryons are nucleons—protons and neutrons. They are followed by the so-called hyperons. The omega-minus hyperon, discovered in 1964, closes the table. It is a heavy particle with a mass of 3273 electron masses. All baryons have spin
The abundance of discovered and newly discovered hadrons led scientists to believe that they were all built from some other more fundamental particles. In 1964, the American physicist M. Gell-Man put forward a hypothesis, confirmed by subsequent research, that all heavy fundamental particles - hadrons - are built from more fundamental particles called quarks. Based on the quark hypothesis, not only was the structure of already known hadrons understood, but the existence of new ones was also predicted. Gell-Mann's theory assumed the existence of three quarks and three antiquarks, connecting with each other in various combinations. Thus, each baryon consists of three quarks, and each antibaryon consists of three antiquarks. Mesons consist of quark–antiquark pairs.
With the acceptance of the quark hypothesis, it was possible to create a harmonious system of elementary particles. However, the predicted properties of these hypothetical particles turned out to be quite unexpected. The electric charge of quarks must be expressed in fractional numbers equal to the elementary charge.
Numerous searches for quarks in the free state, carried out at high-energy accelerators and in cosmic rays, have been unsuccessful. Scientists believe that one of the reasons for the unobservability of free quarks is perhaps their very large masses. This prevents the birth of quarks at the energies that are achieved in modern accelerators. However, most experts are now confident that quarks exist inside heavy particles - hadrons.
Fundamental interactions. The processes in which various elementary particles participate differ greatly in their characteristic times and energies. According to modern concepts, there are four types of interactions in nature that cannot be reduced to others, more simple types interactions: strong, electromagnetic, weak and gravitational. These types of interactions are called fundamental.
The strong (or nuclear) interaction is the most intense of all types of interactions. They provide an extremely strong bond between protons and neutrons in the nuclei of atoms. Only heavy particles—hadrons (mesons and baryons)—can take part in strong interactions. Strong interaction manifests itself at distances of the order of less than 10–15 m. Therefore, it is called short-range.
Electromagnetic interaction. Any electrically charged particles, as well as photons - quanta of the electromagnetic field, can take part in this type of interaction. Electromagnetic interaction is responsible, in particular, for the existence of atoms and molecules. It determines many properties of substances in solid, liquid and gaseous states. Coulomb repulsion of protons leads to instability of nuclei with large mass numbers. Electromagnetic interaction determines the processes of absorption and emission of photons by atoms and molecules of matter and many other processes in the physics of the micro- and macroworld.
Weak interaction is the slowest of all interactions occurring in the microcosm. Any elementary particles except photons can take part in it. Weak interaction is responsible for processes involving neutrinos or antineutrinos, for example, neutron beta decay

As well as neutrino-free particle decay processes with a long lifetime (τ ≥ 10–10 s).
Gravitational interaction is inherent in all particles without exception, however, due to the small masses of elementary particles, the forces of gravitational interaction between them are negligible and their role in the processes of the microworld is insignificant. Gravitational forces play a decisive role in the interaction of space objects (stars, planets, etc.) with their enormous masses.
In the 30s of the 20th century, a hypothesis arose that in the world of elementary particles, interactions are carried out through the exchange of quanta of some field. This hypothesis was originally put forward by our compatriots I. E. Tamm and D. D. Ivanenko. They suggested that fundamental interactions arise from the exchange of particles, similar to covalent chemical bond atoms arise from the exchange of valence electrons, which combine on unfilled electron shells.
The interaction carried out by the exchange of particles is called exchange interaction in physics. For example, electromagnetic interaction between charged particles arises due to the exchange of photons - quanta of the electromagnetic field.
The exchange interaction theory gained recognition after Japanese physicist H. Yukawa theoretically showed in 1935 that the strong interaction between nucleons in atomic nuclei can be explained if we assume that nucleons exchange hypothetical particles called mesons. Yukawa calculated the mass of these particles, which turned out to be approximately equal to 300 electron masses. Particles with such a mass were subsequently actually discovered. These particles are called π-mesons (pions). Currently, three types of pions are known: π+, π– and π0 (see Table 9.9.1).
In 1957, the existence of heavy particles, the so-called vector bosons W+, W– and Z0, was theoretically predicted, causing the exchange mechanism of the weak interaction. These particles were discovered in 1983 in accelerator experiments using colliding beams of high-energy protons and antiprotons. The discovery of vector bosons was a very important achievement in particle physics. This discovery marked the success of the theory, which combined the electromagnetic and weak forces into a single so-called electroweak force. This new theory considers the electromagnetic field and the weak interaction field as different components of one field, in which vector bosons participate along with the electromagnetic field quantum.
After this discovery in modern physics, the confidence that all types of interaction are closely related to each other and, in essence, are different manifestations of some single field has increased significantly. However, the unification of all interactions remains only an attractive scientific hypothesis.
Theoretical physicists make significant efforts in attempts to consider on a unified basis not only the electromagnetic and weak, but also the strong interaction. This theory was called the Great Unification. Scientists suggest that gravitational interaction should also have its own carrier - a hypothetical particle called a graviton. However, this particle has not yet been discovered.
It is now considered proven that a single field that unites all types of interaction can exist only at extremely high particle energies, unattainable with modern accelerators. Particles could have such high energies only in the very early stages of the existence of the Universe, which arose as a result of the so-called big bang(Big Bang). Cosmology - the study of the evolution of the Universe - suggests that the Big Bang occurred 18 billion years ago. In the standard model of the evolution of the Universe, it is assumed that in the first period after the explosion the temperature could reach 1032 K, and the particle energy E = kT could reach 1019 GeV. During this period, matter existed in the form of quarks and neutrinos, and all types of interactions were combined into a single force field. Gradually, as the Universe expanded, the particle energy decreased, and from the unified field of interactions, the gravitational interaction first emerged (at particle energies ≤ 1019 GeV), and then the strong interaction separated from the electroweak interaction (at energies of the order of 1014 GeV). At energies of the order of 103 GeV, all four types of fundamental interactions turned out to be separated. Simultaneously with these processes, the formation of more complex forms of matter took place - nucleons, light nuclei, ions, atoms, etc. Cosmology in its model tries to trace the evolution of the Universe on different stages its development from the Big Bang to the present day, based on the laws of elementary particle physics, as well as nuclear and atomic physics.