QCD Sum Rule Analysis of the Subleading Isgur-Wise Form Factor χ2(v⋅v′)\chi_2(v\cdot v')

We present a QCD sum rule calculation of the spin-symmetry violating universal function $\chi_2(v\cdot v')$, which appears at order $1/m_Q$ in the heavy quark expansion of meson form factors. This function vanishes in the standard approximation, where radiative effects are neglected. For the first time, the complete set of diagrams arising at order $\alpha_s$ is evaluated. In particular, we find $\chi_2(1) = -(3.8\pm 0.4)\%$ at zero recoil, indicating that $1/m_Q$ corrections induced by the chromo-magnetic moment operator are small.Comment: (10 pages, REVTEX, 2 figures not included) SLAC-PUB-5915, WIS-92/70/Sep-P

Two-Loop Renormalization of Heavy--Light Currents at Order 1/m_Q in the Heavy-Quark Expansion

We present exact results, at next-to-leading order in renormalization-group improved perturbation theory, for the Wilson coefficients appearing at order 1/m_Q in the heavy-quark expansion of heavy-light current operators. To this end, we complete the calculation of the corresponding two-loop anomalous dimension matrix. Our results are important for determinations of |V_{ub}| using exclusive and inclusive semileptonic B decays. They are also relevant to computations of the decay constant f_B based on a heavy-quark expansion.Comment: 16 pages, 2 figures; third author added and one reference updated, results unchange

Form Factor Relations for Heavy-to-Light Transitions

Assuming simple properties of the spectator particle in weak decays the form factors of hadronic current matrix elements are shown to be related to a single universal function. The Isgur-Wise result for heavy-to-heavy transitions follows as well as similar relations for heavy-to-light decay processes. The approximation should hold for total energies of the final particle large compared to the confinement scale. A comparison with experimentally determined D-decay form factors and QCD sum rule results for B-decays is very encouraging.Comment: 12 pages, Latex; Relativistic covariant form, results unchanged, references added, to be published in Physics Lett.

Model-Independent Analysis of B -> pi K Decays and Bounds on the Weak Phase gamma

A general parametrization of the amplitudes for the rare two-body decays B -> pi K is introduced, which makes maximal use of theoretical constraints arising from flavour symmetries of the strong interactions and the structure of the low-energy effective weak Hamiltonian. With the help of this parametrization, a model-independent analysis of the branching ratios and direct CP asymmetries in the various B -> pi K decay modes is performed, and the impact of hadronic uncertainties on bounds on the weak phase gamma = arg(Vub*) is investigated.Comment: 34 pages, 18 figures, uses JHEP.cls; submitted to JHE

Impact of Four-Quark Shape Functions on Inclusive B Decay Spectra

It has recently been pointed out that a new class of subleading shape functions involving B-meson matrix elements of non-local four-quark operators contributes at order Lambda_{QCD}/m_b to B->X_u+l+nu decay distributions in the endpoint region. The corresponding functions f_u(omega) and f_v(omega) are estimated using the vacuum-insertion approximation. A numerical analysis of various B->X_u+l+nu decay spectra suggests that these power corrections are very small, below present theoretical uncertainties due to other subleading shape-function contributions.Comment: 8 pages, 2 figures; minor revisions and figure added; version to appear in Eur. Phys. J.

Heavy Quark Symmetry

We review the current status of heavy quark symmetry and its applications to weak decays of hadrons containing a single heavy quark. After an introduction to the underlying physical ideas, we discuss in detail the formalism of the heavy quark effective theory, including a comprehensive treatment of symmetry breaking corrections. We then illustrate some nonperturbative approaches, which aim at a dynamical, QCD-based calculation of the universal form factors of the effective theory. The main focus is on results obtained using QCD sum rules. Finally, we perform an essentially model-independent analysis of semileptonic $B$ meson decays in the context of the heavy quark effective theory.Comment: 186 pages (hardcopy of entire manuscript available upon request), SLAC-PUB-626

Effective Field Theory and Heavy Quark Physics

These notes are based on five lectures presented at the 2004 Theoretical Advanced Study Institute (TASI) on ``Physics in D>=4''. After a brief motivation of flavor physics, they provide a pedagogical introduction to effective field theory, the effective weak Lagrangian, and the technology of renormalization-group improved perturbation theory. These general methods are then applied in the context of heavy-quarks physics, introducing the concepts of heavy-quark and soft-collinear effective theory.Comment: Lectures presented at TASI 2004 (39 pages