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Physics of the nucleus |Физика ядра

Lesson 9

Read the text: Elementary Particle

     In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which all other particles are made. In the Standard Model, the quarks, leptons, and gauge bosons are elementary particles.

     Historically, the hadrons (mesons and baryons such as the proton and neutron) and even whole atoms were once regarded as elementary particles. A central feature in elementary particle theory is the early 20th century idea of "quanta", which revolutionised the understanding of electromagnetic radiation and brought about quantum mechanics.

     All elementary particles are either bosons or fermions (depending on their spin). The spin-statistics theorem identifies the resulting quantum statistics that differentiates fermions from bosons. According to this methodology: particles normally associated with matter are fermions, having half-integer spin; they are divided into twelve flavours. Particles associated with fundamental forces are bosons, having integer spin.

Fermions:

Quarks — up, down, charm, strange, top, bottom

Leptons — electron neutrino, electron, muon neutrino, muon, tauon neutrino, tauon

Bosons:

Gauge bosons — gluon, W and Z bosons, photon

Other bosons — Higgs boson, graviton

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.

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:

 

1. 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.

 

2. 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 ______.