Martin Beneke

QCD factorization for exclusive non-leptonic B-meson decays: General arguments and the case of heavy-light final states

We provide a rigorous basis for factorization for a large class of non-leptonic twobody B-meson decays in the heavy-quark limit. The resulting factorization formula incorporates elements of the naive factorization approach and the hard-scattering approach, but allows us to compute systematically radiative (“non-factorizable”) corrections to naive factorization for decays such as B → Dπ and B → ππ. We first discuss the factorization formula from a general point of view. We then consider factorization for decays into heavy-light final states (such as B → Dπ) in more detail, including a proof of the factorization formula at two-loop order. Explicit results for the leading QCD corrections to factorization are presented and compared to existing measurements of branching fractions and final-state interaction phases.

QCD factorization in B ---> pi K, pi pi decays and extraction of Wolfenstein parameters

Abstract In the heavy-quark limit, the hadronic matrix elements entering nonleptonic B-meson decays into two light mesons can be calculated from first principles including “nonfactorizable” strong-interaction corrections. The B→πK, ππ decay amplitudes are computed including electroweak penguin contributions, SU(3) violation in the light-cone distribution amplitudes, and an estimate of power corrections from chirally-enhanced terms and annihilation graphs. The results are then used to reduce the theoretical uncertainties in determinations of the weak phases γ and α. In that way, new constraints in the ( ρ , η ) plane are derived. Predictions for the B→πK, ππ branching ratios and CP asymmetries are also presented. A good global fit to the (in part preliminary) experimental data on the branching fractions is obtained without taking recourse to phenomenological models.

Soft collinear effective theory and heavy to light currents beyond leading power

Abstract An important unresolved question in strong interaction physics concerns the parameterization of power-suppressed long-distance effects to hard processes that do not admit an operator product expansion (OPE). Recently Bauer et al. have developed an effective field theory framework that allows one to formulate the problem of soft-collinear factorization in terms of fields and operators. We extend the formulation of soft-collinear effective theory, previously worked out to leading order, to second order in a power series in the inverse of the hard scale. We give the effective Lagrangian and the expansion of “currents” that produce collinear particles in heavy quark decay. This is the first step towards a theory of power corrections to hard processes where the OPE cannot be used. We apply this framework to heavy-to-light meson transition form factors at large recoil energy.

Symmetry-breaking corrections to heavy-to-light B meson form factors at large recoil

Recently it has been shown that symmetries emerging in the heavy quark and large recoil energy limit impose various relations on form factors that parameterize the decay of B mesons into light mesons. These symmetries are broken by perturbative effects. In this paper we discuss the structure of heavy-to-light form factors including such effects and compute symmetry-breaking corrections to first order in the strong coupling. As an application of our results we consider the forward–backward asymmetry zero in the rare decay B→Vl+l− and the possibility to constrain potential new physics contributions to the Wilson coefficient C9.

Systematic approach to exclusive B→Vℓ+ℓ−, Vγ decays

We show -- by explicit computation of first-order corrections -- that the QCD factorization approach previously applied to hadronic two-body decays and to form factor ratios also allows us to compute non-factorizable corrections to exclusive, radiative B meson decays in the heavy quark mass limit. This removes a major part of the theoretical uncertainty in the region of small invariant mass of the photon. We discuss in particular the decays B\to K^* \gamma and B\to K^* l^+l^- and complete the calculation of corrections to the forward-backward asymmetry zero. The new correction shifts the asymmetry zero by 30%, but the result confirms our previous conclusion that the asymmetry zero provides a clean phenomenological determination of the Wilson coefficient C_9.

Exclusive radiative and electroweak

Abstract.We provide standard model expectations for the rare radiative decays

b \to d

B\to K^*\gamma

and

,

b \to s

B\to \rho\gamma

penguin decays at NLO

and