Space-like (vs. time-like) collinear limits in QCD: Is factorization violated?

• Autores: Catani, Stefano; de Florian, Daniel Enrique; Rodrigo, Germán
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Hadronic Colliders; Nlo Computations
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We consider the singular behaviour of QCD scattering amplitudes in kinematical configurations where two or more momenta of the external partons become collinear. At the tree level, this behaviour is known to be controlled by factorization formulae in which the singular collinear factor is universal (process independent). We show that this strict (process-independent) factorization is not valid at one-loop and higher-loop orders in the case of the collinear limit in space-like regions (e.g., collinear radiation from initialstate partons). We introduce a generalized version of all-order collinear factorization, in which the space-like singular factors retain some dependence on the momentum and colour charge of the non-collinear partons. We present explicit results on one-loop and two-loop amplitudes for both the two-parton and multiparton collinear limits. At the level of squared amplitudes and, more generally, cross sections in hadron-hadron collisions, the violation of strict collinear factorization has implications on the non-abelian structure of logarithmically-enhanced terms in perturbative calculations (starting from the next-tonext-to-leading order) and on various factorization issues of mass singularities (starting from the next-to-next-to-next-to-leading order). © SISSA 2012.
Fil: Catani, Stefano. Università degli Studi di Firenze; Italia
Fil: de Florian, Daniel Enrique. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina
Fil: Rodrigo, Germán. Consejo Superior de Investigaciones Cientıficas,; España