Complete basis for power suppressed collinear-ultrasoft operators

Dan Pirjol, Iain W. Stewart

Research output: Contribution to journalArticlepeer-review

83 Scopus citations

Abstract

We construct operators that describe power corrections in mixed collinear-ultrasoft processes in QCD. We treat the ultrasoft-collinear Lagrangian to [Formula Presented] and heavy-to-light currents involving collinear quarks to [Formula Presented] including new three body currents. A complete gauge invariant basis is derived which has a full reduction in Dirac structures and is valid for matching at any order in [Formula Presented] The full set of reparametrization invariance (RPI) constraints is included, and is found to restrict the number of parameters appearing in Wilson coefficients and to rule out some classes of operators. The QCD ultrasoft-collinear Lagrangian has two [Formula Presented] operators in its gauge invariant form. For the [Formula Presented] heavy-to-light currents there are [Formula Presented] subleading (scalar, pseudoscalar, vector, axial-vector, tensor) currents, where [Formula Presented] have coefficients that are not determined by RPI. In a frame where [Formula Presented] and [Formula Presented] the total number of currents reduces to [Formula Presented] but the number of undetermined coefficients is the same. The role of these operators and universality of jet functions in the factorization theorem for heavy-to-light form factors is discussed.

Original languageEnglish
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Volume67
Issue number9
DOIs
StatePublished - 2003

Fingerprint

Dive into the research topics of 'Complete basis for power suppressed collinear-ultrasoft operators'. Together they form a unique fingerprint.

Cite this