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A possible goal of fundamental physics is to reduce all natural phenomena to a set of basic laws and theories which, at least in principle, can quantitatively reproduce and predict experimental observations. At the microscopic level all the phenomenology of matter and radiation, including molecular, atomic, nuclear, and subnuclear physics, can be understood in terms of three classes of fundamental interactions: strong, electromagnetic, and weak interactions. For all material bodies on the Earth and in all geological, astrophysical, and cosmological phenomena, a fourth interaction, the gravitational force, plays a dominant role, but this remains negligible in atomic and nuclear physics. In atoms, the electrons are bound to nuclei by electromagnetic forces, and the properties of electron clouds explain the complex phenomenology of atoms and molecules. Light is a particular vibration of electric and magnetic fields (an electromagnetic wave). Strong interactions bind the protons and neutrons together in nuclei, being so strongly attractive at short distances that they prevail over the electric repulsion due to the like charges of protons. Protons and neutrons, in turn, are composites of three quarks held together by strong interactions occur between quarks and gluons (hence these particles are called “hadrons” from the Greek word for “strong”). The weak interactions are responsible for the beta radioactivity that makes some nuclei unstable, as well as the nuclear reactions that produce the enormous energy radiated by the stars, and in particular by our Sun. The weak interactions also cause the disintegration of the neutron, the charged pions, and the lightest hadronic particles with strangeness, charm, and beauty (which are “flavour” quantum numbers), as well as the decay of the top quark and the heavy charged leptons (the muon μ and the tau τ). In addition, all observed neutrino interactions are due to these weak forces.

This chapter is devoted to a concise introduction to quantum chromodynamics (QCD), the theory of strong interactions (Gell-Mann, Acta Phys Austriaca (suppl. IX):733, 1972; Gross and Wilczek, Phys Rev Lett 30:1343, 1973; Weinberg, Phys Rev Lett 31:494, 1973) [for a number of dedicated books on QCD, see Dokshitzer and Khoze (In: Frontieres (ed) Basics of perturbative QCD, 1991), and also Altarelli (QCD: the theory of strong interactions. In: Landolt-Boernstein I 21A: Elementary particles 4. Springer, Berlin, 2008)]. The main emphasis will be on ideas without too many technicalities. As an introduction we present here a broad overview of the strong interactions [for reviews of the subject, see, for example, Altarelli (Phys Rep 81:1, 1982) and Altarelli (Ann Rev Nucl Part Sci 39:357, 1989)]. Then some methods of non-perturbative QCD will be briefly described, including both analytic approaches and simulations of the theory on a discrete spacetime lattice. Then we shall proceed to the main focus of the chapter, that is, the principles and applications of perturbative QCD, which will be discussed in detail.

In this chapter, we summarize the structure of the standard EW theory [Some recent textbooks are listed in Langacker (The standard model and beyond, CRC, Boca Raton, FL, 2010; Paschos, Electroweak theory (Cambridge University Press, Cambridge, 2007); Becchi and Ridolfi, An introduction to relativistic processes and the standard model of electroweak interactions, Springer, Berlin, 2006; Horejsi, Fundamentals of electroweak theory, Karolinum, Prague, 2002; Barbieri, Lectures on the electroweak interactions, Publications of the Scuola Normale Superiore, Pisa, 2007). See also Altarelli (The standard model of electroweak interactions. In: Landolt-Boernstein I 21A: Elementary Particles, vol. 3, Springer, Berlin, 2008) and Quigg (Annu Rev Nucl Part Sci 59:505, 2009).] and specify the couplings of the intermediate vector bosons and and those 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 the Higgs mechanism. 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, Commins, Weak interactions, McGraw Hill, New York, 1973; Okun, Leptons and quarks, North Holland, Amsterdam, 1982; Bailin, Weak interactions, 2nd edn. Hilger, Bristol, 1982; Georgi, Weak and modern particle theory, Benjamin, Menlo Park, CA, 1984).