Sudakov Resummation for Subleading SCET Currents and Heavy-to-Light Form Factors

The hard-scattering contributions to heavy-to-light form factors at largerecoil are studied systematically in soft-collinear effective theory (SCET).Large logarithms arising from multiple energy scales are resummed by matchingQCD onto SCET in two stages via an intermediate effective theory. Anomalousdimensions in the intermediate theory are computed, and their form is shown tobe constrained by conformal symmetry. Renormalization-group evolution equationsare solved to give a complete leading-order analysis of the hard-scatteringcontributions, in which all single and double logarithms are resummed. In twocases, spin-symmetry relations for the soft-overlap contributions to formfactors are shown not to be broken at any order in perturbation theory byhard-scattering corrections. One-loop matching calculations in the twoeffective theories are performed in sample cases, for which the relativeimportance of renormalization-group evolution and matching corrections isinvestigated. The asymptotic behavior of Sudakov logarithms appearing in thecoefficient functions of the soft-overlap and hard-scattering contributions toform factors is analyzed.Comment: 50 pages, 10 figures; minor corrections, version to appear in JHE