Complete Anatomy of B -> K*ll and its angular distribution

We present a complete and optimal set of observables for the exclusive 4-body B meson decay B -> K*(->K pi) l+l- in the low dilepton mass region, that contains a maximal number of clean observables. This basis of observables is built in a systematic way. We show that all the previously defined observables and any observable that one can construct, can be expressed as a function of this basis. This set of observables contains all the information that can be extracted from the angular distribution in the cleanest possible way. We provide explicit expressions for the full and the uniangular distributions in terms of this basis. The conclusions presented here can be easily extended to the large-q^2 region. We study the sensitivity of the observables to right-handed currents and scalars. Finally, we present for the first time all the symmetries of the full distribution including massive terms and scalar contributions.Comment: 37 pages, 12 Figures. Corrected typo in Eqs. (29) and (44). Results and conclusions unchange

QCD and strongly coupled gauge theories : challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe

On B -> V l l at small dilepton invariant mass, power corrections, and new physics

We investigate rare semileptonic \bar B -> \bar K^* l^+ l^- decays, providing a comprehensive treatment of theoretical uncertainties in the low-q^2 region as needed for interpreting current and future LHCb and B-factory data in terms of the new physics search. We go beyond the usual focus on form-factor uncertainties, paying proper attention to non-factorizable terms. A central point is the systematic exploitation of the V-A structure of SM weak interactions, which leads to the suppression of two helicity amplitudes and some of the angular coefficients. We review how this works at the level of (helicity) form factors, and show that the hierarchies extend to non-factorizable terms. For virtual charm effects, we give an argument for it in terms of light-cone QCD sum rules that continues to hold at the level of "long-distance" Lambda_QCD^2/m_c^2 power corrections, reducing an important source of theoretical uncertainty in any \bar B, \bar B_s -> V l^+ l^- (or \bar B -> V gamma) decay. The contributions of the remaining hadronic weak Hamiltonian respect a similar hierarchy. We employ a resonance model to preclude (in the \bar B -> \bar K^* case) large long-distance corrections to this. A phenomenological part pays particular attention to the region of lowest dilepton mass, 4 m_l^2 <= q^2 <= 2 GeV^2. Two observables remain theoretically clean, implying a (theoretical) sensitivity to the real (imaginary) part of the "right-handed" Wilson coefficient C_7' to 10% (1%) of C_7^SM, both in the muonic and the electronic mode. We also show that there are two near-exact relations between angular coefficients, even in the presence of new physics and when lepton masses are not neglected