Experimental Results on Heavy Quarks

Accurate studies of the production and decays of beauty and charm hadrons are exploiting a unique laboratory for testing the Standard Model in the fermion sector, for studying QCD in the non-perturbative regime and for searching for New Physics through virtual processes. The first two items are the main subjects of this paper while the latter is discussed in [ 1]. In the Standard Model, weak interactions among quarks are encoded in a 3 × 3 unitary matrix: the CKM matrix. The existence of this matrix conveys the fact that quarks are a linear combination of mass eigenstates [ 2, 3]. The CKM matrix can be parametrized in terms of four free parameters. These parameters can be measured in several physics processes. In a frequently used parametrization these parameters are named: λ, A, ρ̄ and η̄ . The Standard Model predicts relations between the different processes which depend upon these parameters; CP violation is accomodated in the CKM matrix and its existence is related to η̄ 6= 0. The unitarity of the CKM matrix can be visualized as a triangle in the ρ̄ − η̄ plane. Several quantities, depending upon ρ̄ and η̄ can be measured and they must define compatible values for the two parameters, if the Standard Model is the correct description of these phenomena. Extensions of the Standard Model can provide different predictions for the position of the upper vertex of the triangle, given by the ρ̄ and η̄ coordinates.