Particles and force interactions - Structure of matter Flashcards
What are the two types of matter?
Fields and particles.
According to physical conditions, what are the four phases in which matter in the form of particles can exist?
liquid, gas, solid and plasma phase.
What are the characteristic force interactions for matter in the form of fields (four types)?
Gravitational and electromagnetic field - well known from our surroundings.
Strong and weak nuclear fields - existing in the world of atoms.
Explain how individual forms of matter can mutually transform.
E.g. Formation of electromagnetic wave as a consequence of annihilation of particle with its antiparticle.
An example of the opposite transformation is the creation of the pair electron-positron during absorption of γ-radiation.
What two groups of fundamental particles does the corpuscular form of matter consist of?
The first group involves leptons.
The second involves quarks.
Explain leptons.
Leptons do not interact with the strong nuclear force.
Three different generations can be distinguished in the both groups.
First generation of leptons involve electron and electron neutrino.
Second generation of leptons involves muon and muon neutrino.
Third generation of leptons involves the τ (tau) particle and its neutrino.
Explain quarks.
The generations of quarks differ according to the property called flavour.
There are two quarks of this property in each generation.
The first generation includes quarks u (up) and d (down).
The second generation includes quarks c (charm) and s (strange).
The third generation includes quarks t (top) and b (bottom).
The generations of quarks are also characterised by non-integer electric charge.
The charge of the first quark of each pair is +2/3.
The charge for the second quark of the same generation is -1/3.
A further property of quarks is colour.
Each quark may possess red, green or blue colour.
All fundamental particles, leptons and quarks are also characterized by spin that can be +/-1/2.
An antiparticle exists to each particle.
Antiparticle possesses the opposite electronic charge in the case of flavour and colour are these properties called with the prefic anti-, i.e. we spek about flavours (quarks) antiu, antid, and colours antired, antigreen and antiblue.
Quarks are composed of particles called hadrons. (More on hadrons in other card).
Explain hadrons.
Quarks can form composed particles called hadrons.
Hadrons must fulfil two conditions:
Their electric charge must be integer.
Their combination of colours must be colourless (white).
This may be achieved in two ways:
First group of hadrons are composed of two quarks, quark and antiquark and are called mesons.
Mesons have an integer value of spin.
E.g. The particled called pion π; it is formed by quark u and antiu in the case of medon π0, by quark u and antid in the case of meson π+, and by quark antuu and d in the case of meson π-.
The second group of hadrons are called baryons.
Baryons are composed of three quarks of different colours - red, green and blue.
Baryons have a half value spin.
E.g. proton is formed by two quarks u and one quark d, neutron by two quarks d and one quark u.
Two broad groups of hadrons:
- Fermions
- Bosons
Explain the two groups of elementary particles (fundamental hadrons and quanta of fields).
According to the value of spin, the elementary particles (findamental hadrons and quanta of fields) fall into two large groups.
The first group is represented by fermions characterized by half-value of spin.
Their behaviour can be described by so called Fermi-Dirac statistics.
Their basic property lies in the fact that they behave according to the Pauli’s exclusion principle.
- I.e. no two fermions with identical energies can exist in one system.
The second group contains particles called bosons, these posses integer value spin.
Their behaviour is described by Einstein-Bose statistics.
In the case of bosons, the number of particles at the same energy level is not limited.
Summarise antiparticle characteristics, when compared to particles.
The same mass.
Identical value of spin (integer, non-integer).
Opposite rotation (clockwise, anticlockwise).
Opposite magnetic moment (+ve, -ve) - if half value.
Opposite charge - if not without charge.
Opposite colour (anticolour).
Summerise Hadrons.
Particles composed of quarks:
- Must have integer value charge.
- Must be white (colourless).
Mesons:
- 2 quarks (quark + antiquark)
Integer spin
Pion π:
π0 (u, antiu)
π+ (u, antiu)
π- (antiu, d)
Bayrons:
- 3 quarks.
Half-value spin.
Proton = u(red) + u(green) + d(blue)
Neutron = u(red) + d(green) + d(blue)
Explain the force interaction of all types of fields.
The force interaction of all types of fields possesses the exchange charater, i.e. it is realized by the exchange of quanta of these fields.
Basic Bose particles represent the excitations of these fields.
Thus,
- Photon* corresponds to the electromagnetic field.
- Gluons* (of three different colours) correspond to strong nuclear force.
The particles W± and Z± to weak interaction.
Hypothetical gravitation to gravitational interaction.
The range of gravitational field (source is mass) and of electromagnetic field (source is electric charge) is not limited.
The range of strong interaction (source is colour) is of about 10-15m and the range of weak interaction (enabling the change of the flavour) is of about 10-18m.
The last two we call saturated fields.
At distances corresponding to the size of atomic nuclei, I.e. of about 10-15m, the relative ratios of strong, electromagnetic, weak and gravitational interactions are of 1:10-3:10-15:10-40.
Out of particles with the mass different from zero, only electron and proton are stable ones.
Other particles are unstable.
E.g. Free neutron decays after about 103s by the β- decay into proton, electron and electron antineutrino,
n–> pe- ν’e
This decay corresponds to the transmutation of the quark d into quark u.
Out of particles with non-zero mass, muon μ- possesses the longest life span (2.10-6s).
Most hadrons decay immediately after their formation since they exist for time shorter than 10-12s.
