ABSTRACT
In spite of its enormous success in describing the available experimental data with high accuracy, the standard model discussed in Chapter 3 is generally not believed to be the last step in unification. In particular, there are several parameters that are not predicted as you would expect from theory. For example the standard model contains 18 free parameters which have to be determined experimentally:
• the coupling constants e, αS , sin2 θW , • the boson masses mW , mH , • the lepton masses me, mμ, mτ , • the quark masses mu, md, ms, mc, mb, mt and • the CKM matrix parameters: three angles and a phase δ. Including massive neutrinos would add further parameters. In addition, the mass hierarchy remains unexplained, left-handed and right-handed particles are treated very differently, and the quantization of the electric charge and the equality of the absolute values of proton and electron charge to a level better than 10−21 is not predicted.
