All the available experimental information on open charm and beauty mesons is used to classify the observed states in heavy quark doublets. The masses of some of the still unobserved states are predicted, in particular in the beauty sector. Adopting an effective Lagrangian approach based on the heavy quark and chiral symmetry, individual decay rates and ratios of branching fractions are computed, with results useful to assign the quantum numbers to recently observed charmed states which still need to be properly classified. Implications and predictions for the corresponding beauty mesons are provided. The experimental results are already copious, and are expected to grow up thanks to the experiments at the LHC and to the future high-luminosity flavour and $p-\bar p$ facilities.Comment: RevTex, 15 pages, 1 figure. Corrected Equations (8) and (9

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We use gauge/string duality to investigate the free energy of two static color sources (a heavy quark-antiquark pair) in a Yang-Mills theory in strongly interacting matter, varying temperature and chemical potential. The dual space geometry is Anti-de Sitter with a charged black-hole to describe finite temperature and density in the boundary theory, and we also include a background warp factor to generate confinement. The resulting deconfinement line in the µ − T plane is similar to the one obtained by lattice and effective models of QCD.PACS numbers: 11.25. Tq, 25.75.Nq Consider QCD in a four dimensional Euclidean spacetime and in nuclear matter, and two static color sources, an infinitely heavy quark and an infinitely heavy antiquark, at distance r from each other. It is interesting to investigate how the free energy of such a system behaves against variations of temperature and chemical potential.The study of a strongly coupled Yang-Mills theory, such as QCD, is a challenge in spite of the methods developed so far to deal with it (lattice simulations, models and effective field theories). The formulation of the gauge/gravity (or Anti-de Sitter/conformal field theory) correspondence [1-4] has suggested to face this problem through the identification of a suitable higher dimensional gravity dual. Due to the strong/weak nature of the duality, the gravity dual is a weakly coupled theory defined in a higher dimensional curved spacetime; since QCD is not conformal, a mechanism for breaking conformal invariance must be included in the dual model. This holographic framework can be adopted to analyze finite temperature and density effects. In a bottomup approach, we use the soft wall AdS/QCD model, a five dimensional model formulated on AdS 5 spacetime, in which linear confinement at zero temperature and density is obtained by inserting a background warp factor [5][6][7], bringing a mass scale related to Λ QCD . To describe the boundary theory at finite temperature, a black-hole is included in the five dimensional space, whose horizon position represents the (inverse) temperature [4].On the other hand, in QCD the effect of finite quark density is introduced by adding the term J D = µ ψ † (x)ψ(x) to the Lagrangian in the generating functional, so that the chemical potential µ appears as the source of the quark density operator. According to the AdS/CFT correspondence, the source of a QCD operator in the generating functional is the boundary value of a dual field in the bulk; therefore, the chemical potential can be considered as the boundary value of the time component of a U (1) gauge field A M dual to the vector quark current. Under the ansatz A 0 = A 0 (z) (z is the fifth holographic coordinate) and A i = A z = 0 (i = 1, 2, 3), one can find a solution of the equations of motion of a 5D gravity action with negative cosmological constant interacting with an electromagnetic field: the solution is known as the AdS/Reissner-Nordström black-hole metric, and describes a charged black hole interacting with the electromag...