Space-like (vs. time-like) collinear limits in QCD: is factorization violated?
By S. Catani, D. Florian, G. Rodrigo. 2011
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A bstractWe 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 initial-state 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-to-next-to-leading order) and on various factorization issues of mass singularities (starting from the next-to-next-to-next-to-leading order).
Subfields: Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/6adb3eb7c19f9ab2c6158dfef0ab45dedbf0cd74
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In Nuclear and High Energy Physics
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- Looking Inside Jets (2019, background): “nsverse momentum pt. In that case, we will be able to identify Q min = m. 1However, examples of short-distance processes that exhibits collinear factorisation breaking have been identied and studied [24,25,26,27]. CHAPTER 2. INTRODUCTION TO QCD AT COLLIDERS 15 Protons consist of many partons, each c”
- The Lund jet plane (2018, background): “enhancements, i.e. terms of the form n sL m where Lmay generically be either ln1= or ln1 =. Ignoring potential subleading-N c factorisation violation issues, or equivalently super-leading logarithms [63,64], there are strong reasons to believe that with the C/A algorithm the highest logarithmic enha”
- Boosted objects and jet substructure at the LHC. Report of BOOST2012, held at IFIC Valencia, 23rd–27th of July 2012 (2013, background): “,31] for the case of CambridgeAachen and k talgorithms. Furthermore, recent studies have shown that strict collinear factorization is violated if the observable considered is not suciently inclusive [32,33]. As a consequence, coherence-violating (or super-leading) logarithms appear, which further co”