Leptonic Interactions

Question 1

What are virtual particles, and why are they called “virtual”?

Answer 1

Virtual particles are particles that appear as intermediate states in Feynman diagrams but cannot be directly observed in isolation in free space. They are called “virtual” because they violate energy conservation and exist only transiently within the framework of quantum field theory.

Question 2

What are Feynman diagrams, and what do they represent in particle interactions?

Answer 2

Feynman diagrams are graphical representations used to depict particle interactions. They represent the basic processes involved, such as particle emission, absorption, and exchange.

Question 3

What conservation laws are associated with each generation of leptons in the standard model?

Answer 3

Each generation of leptons is associated with a conservation law: electron lepton number (Le), muon lepton number (Lµ), and tau lepton number (Lτ).

Question 4

Describe the basic vertices for weak interactions involving Z0 boson exchange.

Answer 4

The basic vertices for Z0 interactions involve the emission or absorption of a Z0 boson by a lepton. These interactions conserve charge and lepton number at each vertex.

Question 5

What characterizes the strength of weak interactions, and how is it related to the mass of the exchange particle?

Answer 5

The strength of weak interactions is characterized by the Fermi coupling constant (GF). It is related to the mass of the exchange particle (MW) through the equation GF √2 = (4παW) / (MW c^2)^2, where αW is a dimensionless parameter analogous to the fine structure constant.

Question 6

Charged current interaction

Answer 6

Weak interactions involving W+- bosons

Question 7

Neutral current interaction

Answer 7

Weak interaction involving Z0 bosom