Standard Model

The Standard Model of particle physics contains 12 flavors of elementary fermions, plus their corresponding antiparticles, as well as elementary bosons that mediate the forces and the still undiscovered Higgs boson. However, the Standard Model is widely considered to be a provisional theory rather than a truly fundamental one, since it is fundamentally incompatible with Einstein's general relativity. There are likely to be hypothetical elementary particles not described by the Standard Model, such as the graviton, the particle that would carry the gravitational force or the sparticles, supersymmetric partners of the ordinary particles.

Fundamental fermions

The 12 fundamental fermionic flavours are divided into three generations of four particles each. Six of the particles are quarks. The remaining six are leptons, three of which are neutrinos, and the remaining three of which have an electric charge of −1: the electron and its two cousins, the muon and the tauon.

Particle Generations
Leptons
First generation		Second generation		Third generation
Name	Symbol	Name	Symbol	Name	Symbol
electron	e−	muon	μ−	tauon	τ−
electron neutrino	νe	muon neutrino	νμ	tauon neutrino	ντ
Quarks
First generation		Second generation		Third generation
up quark	u	charm quark	c	top quark	t
down quark	d	strange quark	s	bottom quark	b

Antiparticles

There are also 12 fundamental fermionic antiparticles which correspond to these 12 particles. The antielectron (positron) e⁺ is the electron's antiparticle and has an electric charge of +1 and so on:

Particle Generations
Antileptons
First generation		Second generation		Third generation
Name	Symbol	Name	Symbol	Name	Symbol
antielectron (positron)	e+	muon	μ+	tauon	τ+
electron antineutrino	νe	muon antineutrino	νμ	tauon antineutrino	ντ
Antiquarks
First generation		Second generation		Third generation
up antiquark	u	charm antiquark	c	top antiquark	t
down antiquark	d	strange antiquark	s	bottom antiquark	b

I. Reading exercises:

Exercise1. Read and memorize using the dictionary:

substructure, quarks, leptons, gauge bosons, hadrons, mesons, baryons, fermions, spin statistic theorem, identify with, differentiate, half-integer spin, integer spin, mediate, Higgs boson, provisional theory, incompatible, supersymmetric partners, fundamental fermions, muons, tauons, flavours, antiparticles

Exercise 2. Answer the questions:

1. What are the quarks, leptons and gauge bosons in the Standard Model?

2. What are all elementary particles – either bosons or fermions – depending on?

3. How many flavours of elementary fermions does the Standard Model of particle physics contain?

4. What is divided into three generations of four particles each?

5. How many fundamental fermionic antiparticles are there?

Exercise 3. Match the left part with the right:

1. In the Standard Model the quarks, leptons and gauge bosons	a. correspond to these 12 particles.
2. The Standard Model of particle physics contains	b. into three generations of four particles each.
3. The 12 fundamental fermionic flavours are divided	c. 12 flavours of elementary fermions.
4. There are also 12 fundamental fermionic antiparticles which	d. are elementary particles.

Exercise 4. Open brackets using the right words:

All elementary particles are either bosons or fermions (relying/depending) on their spin. The spin-statistics theorem (supports/identifies) the resulting quantum statistics that (differentiates/distinguishes) fermions from bosons.

The Speaking Module

II. Speaking exercises:

Exercise 1. Describe particle physics; electromagnetic radiation; graviton; fermion using the suggested words and expressions:

particle physics concerned with; the branch of physics; understanding the properties and behaviour; especially through study of collisions; of elementary particles; or decays; involving energy of hundreds of mega electron volts example: Particle physics – the branch of physics concerned with understanding the properties and behaviour of elementary particles, especially through study of collisions or decay involving energy hundreds of mega electron volts.

electromagnetic radiation and especially the associated electromagnetic energy; electromagnetic waves

graviton postulated as the quantum; a theoretically deduced particle; of the gravitational field; having a rest mass and charge of zero and a spin of 2

fermion such as the electron, proton or neutron; a particle; that the wave function of several identical particles; which obeys the rule; changes sign; when the coordinates of any pair are interrelated

Exercise 2. Ask questions to the given answers:

1. Question: ____________________________________ ?

Answer: Historically, the hadrons (mesons and baryons such as the proton and neutron) and even whole atoms were once regarded as elementary particles.

2. Question: ____________________________________ ?

Answer: A central feature in elementary particle theory is the early 20th century idea of "quanta".

3. Question: ____________________________________ ?

Answer: The Standard Model is widely considered to be a provisional theory rather than a truly fundamental one.

The Writing Module

III. Writing exercises:

Exercise 1. Complete the sentences with the suggested words: as well as; boson; model; contains; widely; fermions; forces; rather; relativity; since:

The Standard ______ of particle physics ______ 12 flavors of elementary ______, plus their corresponding antiparticles, ______ elementary bosons that mediate the ______ and the still undiscovered Higgs ______. However, the Standard Model is ______ considered to be a provisional theory ______ than a truly fundamental one, ______ it is fundamentally incompatible with Einstein's general ______

.Exercise 2. Fill in the table with words from the text. Group the synonyms:

know	little
make up	fundamental
small	comprise
truly	depict
describe	separate
basic	recognize
feature	put together
spin	really
contain	characteristic
divide	bear
carry	rotate

Exercise 3. Compose a story on one of the topics (up to 100 words):

“Standard Model”

“Fundamental fermions”

“Antiparticles”

Lesson 10

The Reading Module

Read the text: Quarks

Quarks and antiquarks have never been detected to be isolated, a fact explained by confinement. Every quark carries one of three color charges of the strong interaction; antiquarks similarly carry anticolor. Color charged particles interact via gluon exchange in the same way that charged particles interact via photon exchange. However, gluons are themselves color charged, resulting in an amplification of the strong force as color charged particles are separated. Unlike the electromagnetic force which diminishes as charged particles separate, color charged particles feel increasing force.

However, color charged particles may combine to form color neutral composite particles called hadrons. A quark may pair up to an antiquark: the quark has a color and the antiquark has the corresponding anticolor. The color and anticolor cancel out, forming a color neutral meson. Alternatively, three quarks can exist together, one quark being "red", another "blue", another "green". These three colored quarks together form a color-neutral baryon. Symmetrically, three antiquarks with the colors "antired", "antiblue" and "antigreen" can form a color-neutral antibaryon.

Quarks also carry fractional electric charges, but since they are confined within hadrons whose charges are all integral, fractional charges have never been isolated. Note that quarks have electric charges of either +2/3 or −1/3, whereas antiquarks have corresponding electric charges of either −2/3 or +1/3.

Evidence for the existence of quarks comes from deep inelastic scattering: firing electrons at nuclei to determine the distribution of charge within nucleons (which are baryons). If the charge is uniform, the electric field around the proton should be uniform and the electron should scatter elastically. Low-energy electrons do scatter in this way, but above a particular energy, the protons deflect some electrons through large angles. The recoiling electron has much less energy and a jet of particles is emitted. This inelastic scattering suggests that the charge in the proton is not uniform but split among smaller charged particles: quarks.

Fundamental bosons

In the Standard Model, vector (spin-1) bosons (gluons, photons, and the W and Z bosons) mediate forces, while the Higgs boson (spin-0) is responsible for particles having intrinsic mass.

Gluons

Gluons are the mediators of the strong interaction and carry both colour and anticolour. Although gluons are massless, they are never observed in detectors due to colour confinement; rather, they produce jets of hadrons, similar to single quarks. The first evidence for gluons came from annihilations of electrons and antielectrons at high energies which sometimes produced three jets — a quark, an antiquark, and a gluon.

Electroweak bosons

There are three weak gauge bosons: W⁺, W⁻, and Z⁰; these mediate the weak interaction. The massless photon mediates the electromagnetic interaction.

Higgs boson

Although the weak and electromagnetic forces appear quite different to us at everyday energies, the two forces are theorized to unify as a single electroweak force at high energies. This prediction was clearly confirmed by measurements of cross-sections for high-energy electron-proton scattering at the HERA collider at DESY. The differences at low energies is a consequence of the high masses of the W and Z bosons, which in turn are a consequence of the Higgs mechanism. Through the process of spontaneous symmetry breaking, the Higgs selects a special direction in electroweak space that causes three electroweak particles to become very heavy (the weak bosons) and one to remain massless (the photon). Although the Higgs mechanism has become an accepted part of the Standard Model, the Higgs boson itself has not yet been observed in detectors. Indirect evidence for the Higgs boson suggests its mass lies below 200-250 GeV. In this case, the LHC experiments may be able to discover this last missing piece of the Standard Model.

I. Reading exercises:

Exercise1. Read and memorize using the dictionary:

confinement, limitation, strong interaction, similarly, via, gluon, amplification, diminish, composite particles, hadrons, pair up, cancel out, meson, baryon, antibaryon, fractional, confine, within, integral, evidence, deep in elastic scattering, firing, deflect, angles, recoiling, jet of particles, uniform, intrinsic, mediator, massless, detector, color confinement, annihilations of electrons, weak gauge bosons, weak interaction, Higgs mechanism, spontaneous symmetry breaking

Exercise 2. Answer the questions:

1. What do these three colored quarks together form?

2. What do quarks also carry?

3. When should the electric field around the proton be uniform?

4. What are the mediators of the strong interaction?

5. What do the gluons carry?

Exercise 3. Match the left part with the right:

1. Every quark carries one of three color charges	a. a color-neutral baryon.
2. However, color charged particles may combine	b. forming a color neutral meson.
3. The color and anticolor cancel out,	c. to form color neutral composite particles called hadrons.
4. These three colored quarks together form	d. of the strong interactions.

Exercise 4. Open brackets using the right words:

Quarks also (bear/carry) fractional electric charges, but since they are (confined/interned) within (mesons/hadrons) whose charges are all (universal/integral), fractional charges have never been (separated/isolated).

The Speaking Module

II. Speaking exercises:

Exercise 1. Describe quark; boson; Higgs boson; Higgs mechanism; gluon; photon using the suggested words and expressions:

quark having charges; one of the hypothetical basic particles; whose magnitudes are 1/3 or 2/3 of the electron charge; in theory may be built up; from which many of the elementary particles example: Quarks – one of the hypothetical basic particles having charges whose magnitudes are one-third or two-thirds of the electron charge, from which many of the elementary particles in theory may be built.

boson obeys Bose-Einstein statistics; a particle that; includes photons, pi mesons and all nuclei; having an even number of particles with integer spin

Higgs boson whose existence; massive scalar mesons; is predicted by; of the weak and electromagnetic interactions; certain unified gage theories

Higgs mechanism that the goldstone bosons do not appear as physical particles; the feature of the spontaneously broken gage symmetries.

gluons hypothetical massive particles; one of eight; with spin quantum number; that mediate; and negative parity; strong interactions between quarks

photon the quantum of the electromagnetic field; a massless particle; carrying energy; and angular momentum; momentum

Exercise 2. Ask questions to the given answers:

1. Question: ____________________________________ ?

Answer:

Evidence for the existence of quarks comes from deep inelastic scattering.

2. Question: ____________________________________ ?

Answer: In the Standard Model vector, bosons, gluons, photons and the W and Z bosons mediate forces.

3. Question: ____________________________________ ?

Answer: The Higgs boson (spin-0) is responsible for particles having intrinsic mass.

4. Question: ____________________________________ ?

Answer: The first evidence for gluons came from annihilations of electrons and antielectrons at high energies.

The Writing Module

III. Writing exercises:

Exercise 1. Complete the sentences with the suggested words: at; high; weak; two; appear; unify:

Although the ______ and electromagnetic forces ______ quite different to us ______ everyday energies, the ______ forces are theorized to ______ as a single electroweak force at ______ energies.

Exercise 2. Fill in the table with words from the text. Group the synonyms:

detect	limitation
isolated	decrease
confinement	subsist
carry	dispensation
amplification	reconciler
diminish	find
combine	insulated
cancel	overstatement
exist	obliterate
integral	proof
evidence	test
distribution	bring
deflect	unite
mediator	entire
direction	divert
experiment	guidance

Exercise 3. Compose a story on one of the topics (up to 100 words):

“Fundamental bosons”

“Electroweak bosons. W and Z bosons”

“Higgs bosons”