Particle Experiments X (3872) Babar, Belle, CDF, D0, LHCb G (3900) Babar, Belle Y (4260) Babar, Belle, CLEO Y (4360) Babar, Belle Z ± c (3895) Belle, BES-III, CLEO Table 1.2: Experimentally confirmed heavy quarkonium-like states. In all cases the number in parentheses indicates the mass in units of MeV. This system of units is called natural units and is discussed in Appendix A. this thesis. 1.2 Hadronic Physics 1.2.1 The Standard Model The Standard Model (SM) of particle physics is an extremely successful theoretical framework that describes all fundamental interactions in nature at the quantum level, apart from gravity. The particle content of the SM is shown in Fig. 1.1. There are three main categories of particles: spin-1 gauge bosons ( g , γ , W , Z ), spin-1/2 leptons ( e , µ , τ , ν$_{e}$ , ν$_{µ}$ , ν$_{τ}$ ), and spin- 1/2 quarks ( u , d , s , c , b , t ). Because they mediate interactions between particles in quantum field theory, gauge bosons are often referred to as force carriers. Leptons are particles that do not experience the strong nuclear force, such as the electron. All of the particles in Fig. 1.1 have been confirmed experimentally. However, the SM also predicts the existence of an additional particle known as the Higgs boson. On July 4, 2012, the ATLAS [1] and CMS [30] collaborations announced the discovery of a particle that is likely to be the Higgs boson. Observation of the Higgs boson is a crucial test of the Higgs mechanism, which is essential to the SM. Experimental work to precisely determine the properties of this particle is ongoing. 3