# Particle Physics, Interaction Lagrangian Su(2) X U(1), Electroweak theory.

Deadline 23rd April 2013

This is the baisic outline of the problem, but I will upload the actual question sheet.

1) Solve the interaction Lagrangian to show the interactions between the Z boson with quarks.

2) Derive expressions (in terms of the Weinberg angle) for the decay rate of Z to each type of quark and lepton.

Evaluate these decay rates (in units of GeV; remember these formulae are quoted in

h = c = 1 units). Add them up to show that the total decay rate of the Z (i.e. the width

of the Z resonance) is 2.5 GeV.

Specific requirements:

Must have step by step workings and adhere to the form of the Lagrangian in the question. No index notation to be used.

Second question requires that:

CL for neutrinos = 1/2

CL for electrons = -1/2 + Sin^2(Theta_w)

CR for electrons = Sin^2(Theta_w)