QCD Sum Rules, a Modern Perspective

An introduction to the method of QCD sum rules is given for those who want to learn how to use this method. Furthermore, we discuss various applications of sum rules, from the determination of quark masses to the calculation of hadronic form factors and structure functions. Finally, we explain the idea of the light-cone sum rules and outline the recent development of this approach.Comment: 84 pages, 14 figures, Latex,epsfig,sprocl.sty. To be published in the Boris Ioffe Festschrift ''At the Frontier of Particle Physics / Handbook of QCD'', edited by M. Shifman (World Scientific, Singapore, 2001)

Rare semileptonic B→K∗ℓ+ℓ−B\to K^* \ell^+ \ell^- decays in RSc_c model

Recent LHCb measurements show small discrepancies with respect to the Standard Model (SM) predictions in selected angular distributions of the mode $B^0 \to K^{*0} \mu^+ \mu^-$. The possibility of explaining such tensions within theories beyond the SM crucially depends on the size of the deviations of the Wilson coefficients of the effective Hamiltonian for this mode, in comparison to their SM values. We analyse this issue in the framework of the Randall Sundrum model with custodial protection (RS$_c$); in our study we also consider the mode with $\tau$ leptons in the final state. We discuss the small deviations of RS$_c$ results from SM ones, found scanning the parameter space of the model.Comment: RevTex, 18 pages,18 figures. Published versio

Exotic JPC=1−+J^{PC}=1^{-+} mesons in a holographic model of QCD

Mesons with quantum numbers $J^{PC}=1^{-+}$ cannot be represented as simple quark-antiquark pairs. We explore hybrid configurations in the light meson sector comprising a quark, an antiquark and an excited gluon, studying the properties of such states in a phenomenological model inspired by the gauge/gravity correspondence. The computed mass, compared to the experimental mass of the $1^{-+}$ candidates $\pi_1(1400)$, $\pi_1(1600)$ and $\pi_1(2015)$, favous $\pi_1(1400)$ as the lightest hybrid state. An interesting result concerns the stability of hybrid mesons at finite temperature: they disappear from the spectral function (i.e. they melt) at a lower temperature with respect to other states, light vector and scalar mesons, and scalar glueballs.Comment: 11 pages, 7 figure

Nonleptonic BsB_s to charmonium decays: analyses in pursuit of determining the weak phase βs\beta_s

We analyze nonleptonic $B_s$ decays to a charmonium state and a light meson, induced by the $b \to c {\bar c}s$ transition, which are useful to access the $B_s$-${\bar B}_s$ mixing phase $\beta_s$. We use generalized factorization and $SU(3)_F$ symmetry to relate such modes to correspondent $B$ decay channels. We discuss the feasibility of the measurements in the various channels, stressing the importance of comparing different determinations of $\beta_s$ in view of the hints of new physics effects (NP) recently emerged in the $B_s$ sector. Finally, adopting a general parametrization of NP contributions to the decay amplitudes, we discuss how to experimentally constrain new physics parameters.Comment: LaTeX, 17 pages, 2 Eps figure

Open charm meson spectroscopy: Where to place the latest piece of the puzzle

We discuss how to classify the $c{\bar s}$ meson $D_{sJ}(3040)$ recently discovered by the BaBar Collaboration. We consider four possible assignments, together with signatures useful to distinguish among them.Comment: RevTeX, 5 pages, 1 eps figur