Chapter 3
The Standard Model of Electroweak
Interactions
Guido Altarelli and Stefano Forte
3.1 Introduction
In this chapter, 1 we summarize the structure of the standard EW theory [1]
and specify the couplings of the intermediate vector bosons W ± , Z and of the
Higgs particle with the fermions and among themselves, as dictated by the gauge
symmetry plus the observed matter content and the requirement of renormalizability.
We discuss the realization of spontaneous symmetry breaking and of the Higgs
mechanism [2]. We then review the phenomenological implications of the EW
theory for collider physics (that is we leave aside the classic low energy processes
that are well described by the “old” weak interaction theory (see, for example, [3])).
Moreover, a detailed description of experiments for precision tests of the EW theory
is presented in Chap. 6.
For this discussion we split the lagrangian into two parts by separating the terms
with the Higgs field:
L = L gauge + L Higgs .
(3.1)
Both terms are written down as prescribed by the SU (2) ⊗ U(1) gauge symmetry
and renormalizability, but the Higgs vacuum expectation value (VEV) induces the
The author “G. Altarelli” is deceased at the time of publication.
1 See Chap. 2 for a general introduction to Chap. 2–4 with updated references.
G. Altarelli
University of Rome 3, Rome, Italy
S. Forte ()
Dipartimento di Fisica, Università di Milano, Milano, Italy
© The Author(s) 2020
H. Schopper (ed.), Particle Physics Reference Library,
https://doi.org/10.1007/978-3-030-38207-0_3
35
The Standard Model of Electroweak
Interactions
Guido Altarelli and Stefano Forte
3.1 Introduction
In this chapter, 1 we summarize the structure of the standard EW theory [1]
and specify the couplings of the intermediate vector bosons W ± , Z and of the
Higgs particle with the fermions and among themselves, as dictated by the gauge
symmetry plus the observed matter content and the requirement of renormalizability.
We discuss the realization of spontaneous symmetry breaking and of the Higgs
mechanism [2]. We then review the phenomenological implications of the EW
theory for collider physics (that is we leave aside the classic low energy processes
that are well described by the “old” weak interaction theory (see, for example, [3])).
Moreover, a detailed description of experiments for precision tests of the EW theory
is presented in Chap. 6.
For this discussion we split the lagrangian into two parts by separating the terms
with the Higgs field:
L = L gauge + L Higgs .
(3.1)
Both terms are written down as prescribed by the SU (2) ⊗ U(1) gauge symmetry
and renormalizability, but the Higgs vacuum expectation value (VEV) induces the
The author “G. Altarelli” is deceased at the time of publication.
1 See Chap. 2 for a general introduction to Chap. 2–4 with updated references.
G. Altarelli
University of Rome 3, Rome, Italy
S. Forte ()
Dipartimento di Fisica, Università di Milano, Milano, Italy
© The Author(s) 2020
H. Schopper (ed.), Particle Physics Reference Library,
https://doi.org/10.1007/978-3-030-38207-0_3
35